catalysts

Article Ene-yne Cross-Metathesis for the Preparation of 2,3-Diaryl-1,3-

Meriem K. Abderrezak 1,2, Zahia Kabouche 1, Christian Bruneau 2,* and Cédric Fischmeister 2,* ID

1 Laboratory of Therapeutic Substances Obtention (LOST), Department of Chemistry, Université Frères Mentouri Constantine, Chaabet Ersas Campus, Constantine 25000, Algeria; [email protected] (M.K.A.); [email protected] (Z.K.) 2 UMR6226 CNRS, Institut des Sciences Chimiques de Rennes, Université de Rennes 1, Organometallics: Materials and , Centre for Catalysis and Green Chemistry, Campus de Beaulieu, 35042 Rennes CEDEX, France * Correspondence: [email protected] (C.B.); cedric.fi[email protected] (C.F.); Tel.: +33-2-23-23-62-83 (C.B.); +33-2-23-23-59-98 (C.F.)

Received: 10 November 2017; Accepted: 21 November 2017; Published: 27 November 2017

Abstract: Ene-yne cross-metathesis from and ethylene is a useful method to produce substituted conjugated derivatives. If this method has been used with aliphatic alkynes, it has however never been used starting from diarylacetylenes as internal alkynes. We show that the ene-yne cross-metathesis catalyzed by the second generation Hoveyda ruthenium catalyst provides the 2,3-diarylbuta-1,3-dienes under 3 atm of ethylene at 100 ◦C. The scope and limitations of the reaction have been evaluated starting from unsymmetrical functionalized diarylacetylene derivatives hence leading to unsymmetrical 2,3-diarylbuta-1,3-dienes in a straightforward and environmentally acceptable manner.

Keywords: 1,3-dienes; ene-yne metathesis; ruthenium catalysis

1. Introduction Depending on the substitution pattern of the 1,3- motif, different families of products in terms of electron delocalization are available. 2,3-Diarylbuta-1,3-dienes A consisting of branched π-electron frameworks are cross-conjugated compounds related to (4)-dendralenes featuring two terminal double bonds (Figure1) [ 1], whereas 1,3- that are di-substituted in 1,4-position by aryl groups lead to highly conjugated compounds B with alternating single and double bonds. The 1,1-, 1,2-, and 1,3-diphenylbuta-1,3-dienes (C–E) present at the same time three conjugated double bonds and a cross-conjugated (3)-dendralene structure. Because of their conjugated 1,3-diene structure, these products are perfect starting substrates for the construction of complex molecules [2–4]. Besides the classical [4 + 2] cycloadditions, 1,3-butadiene itself and aliphatic 1,3-butadiene substrates have been efficiently transformed via transition metal-catalyzed reactions. Among them, ruthenium-catalyzed addition of aldehydes [5] and [6], nickel-catalyzed multicomponent coupling with alkynes or aldehydes and dimethylzinc in the presence of carbon dioxide [7,8], rhodium-catalyzed asymmetric [4 + 3] cycloaddition with vinylcarbenoids [9], palladium-catalyzed telomerization with various nucleophiles [10–12], hydroamination [13,14] and hydroamidocarbonylation [15], are representative examples. However, monoarylated 1,3-dienes have been used for triflic acid-catalyzed synthesis of indenes [16], ruthenium-catalyzed isomerization [17], palladium-catalyzed hydroarylation with boronic esters [18], cobalt-catalyzed hydrosilylation [19], asymmetric hydrovinylation with ethylene [20] and enantioselective cycloaddition with internal alkynes [21]. 2-Aryl- and 2,3-diaryl-dienes of type A have been extensively studied for the access to cyclic products resulting from Diels–Alder [4,22]

Catalysts 2017, 7, 365; doi:10.3390/catal7120365 www.mdpi.com/journal/catalysts Catalysts 2017, 7, 365 2 of 9 Catalysts 2017, 7, 365 2 of 9

Theyand hetero-Diels–Alder have also been recently reactions involved [23,24]. Theyin iridium have also‐catalyzed been recently hydrohydroxymethylation involved in iridium-catalyzed [25] and rutheniumhydrohydroxymethylation‐catalyzed hydroxymethylation [25] and ruthenium-catalyzed [26]. hydroxymethylation [26].

Figure 1. Different types of disubstituted 1,3-butadienes.1,3‐butadienes.

Elimination reactions reactions such such as as the the thermal thermal decomposition decomposition of of 3,4 3,4-diaryldihydrothiophene-‐diaryldihydrothiophene‐1, 1,1-dioxides1‐dioxides [27] [27 and] and the the acid acid-catalyzed‐catalyzed dehydration dehydration of 1,2 of‐diol 1,2-diol derivatives derivatives [28] have [28] been have used been for used the synthesisfor the synthesis of 2,3‐ ofdiaryl 2,3-diaryl-buta-1,3-dienes‐buta‐1,3‐dienes of type of type A. ABut. But-2-yn-1,4-diol‐2‐yn‐1,4‐diol biscarbonates biscarbonates have have been efficientlyefficiently coupled with aryl and heteroaryl boronic acids in the presence of a palladium catalyst to give 2,3-diarylated2,3‐diarylated 1,3 1,3-dienes‐dienes [1,29,30]. [1,29,30]. 1,4 1,4-Dimethoxybut-2-yne‐Dimethoxybut‐2‐yne was was also also found found to to be an excellent substrate for the copper(I)-catalyzedcopper(I)‐catalyzed SN2’substitution with aryl Grignard reagents to produce symmetrical 2,3 2,3-diarylbuta-1,3-dienes‐diarylbuta‐1,3‐dienes [31]. [31]. Symmetrical 2,3 2,3-diaryl-1,3-dienes‐diaryl‐1,3‐dienes AA have also been obtained byby homocoupling homocoupling methods methods starting starting directly directly from ketones from orketones the corresponding or the corresponding hydrazones. Thesehydrazones. homocoupling These homocoupling reactions have reactions been performed have been directly performed from acetophenone directly from substrates acetophenone upon substratestreatment with upon SmI treatment2/Ac2O[ 32with], or fromSmI2/Ac the2O derived [32], hydrazonesor from the following derived a hydrazones copper-mediated following Shapiro a copperreaction‐mediated [33] or palladium-catalyzed Shapiro reaction [33] coupling or palladium under‐catalyzed oxidative coupling conditions under [34, 35oxidative]. The preparation conditions [34,35].of 2,3-diaryllbuta-1,3-diene The preparation of 2,3 derivatives‐diaryllbuta has‐1,3 been‐diene achieved derivatives by has homocoupling been achieved of styrylmagnesiumby homocoupling ofbromide styrylmagnesium in the presence bromide of an organocatalystin the presence [36 of], an styryl organocatalyst bromide catalyzed [36], styryl by Pd/C bromide in the catalyzed presence by of Pd/Cindium in [the37], presence and styrylboronic of indium acid [37], catalyzed and styrylboronic by a palladium(II) acid catalyzed complex by a in palladium(II) the presence complex of KMnO in4 theor oxygen presence as of oxidant KMnO [384 or]. Theoxygen same as symmetrical oxidant [38]. 1,3-dienes The same cansymmetrical be obtained 1,3 by‐dienes palladium-catalyzed can be obtained bycross-coupling palladium‐catalyzed of 2,3-bis(pinacolatoboryl)buta-1,3-diene cross‐coupling of 2,3‐bis(pinacolatoboryl)buta with aryl iodides‐1,3 under‐diene basic with conditions aryl iodides [39]. underIt is noteworthy basic conditions that the[39]. preparation It is noteworthy of unsymmetrical that the preparation 2,3-diarylbuta-1,3-dienes of unsymmetrical 2,3 with‐diarylbuta different‐1, 3aryl‐dienes groups, with is different much less aryl documented. groups, is much The less few documented. reported methods The few rely reported on palladium-catalyzed methods rely on palladiumcross-coupling‐catalyzed of p-tolyl cross iodide‐coupling with of 3-silyl-3-phenylbuta-1,3-diene p‐tolyl iodide with 3‐silyl‐3‐phenylbuta in 40% yield‐1,3 [‐39diene] and in styryl 40% yieldtriflates [39] with and styryl styryl boronates triflates with [40]. Anstyryl unsymmetrical boronates [40]. 2,3-bis(2-nitrophenyl)-1,3-butadiene An unsymmetrical 2,3‐bis(2‐nitrophenyl) derivative‐1, 3has‐butadiene been prepared derivative in 61% has yieldbeen byprepared a Pd-catalyzed in 61% yield Stille by cross-coupling a Pd‐catalyzed [41 Stille], whereas cross‐coupling the tentative [41], whereascross-coupling the tentative of two different cross‐coupling hydrazones of ledtwo to different modest yieldshydrazones in the unsymmetrical led to modest product yields besidesin the unsymmetricalthe symmetrical product ones [16 besides]. Because the itsymmetrical is a straightforward ones [16]. atom Because economic it is a reaction, straightforward ene-yne atom cross economicmetathesis reaction, has been appliedene‐yne ascross an efficient metathesis method has for been the constructionapplied as an of 1,3-dienesefficient method [4,42–45 ].for Using the constructionethylene as olefinic of 1,3‐dienes substrate [4,42–45]. allows theUsing production ethylene of as buta-1,3-dienes olefinic substrate with allows two terminal the production methylene of butagroups‐1,3 according‐dienes with to atwo catalytic terminal cycle methylene initially proposedgroups according by M. Mori to a [catalytic46] and furthercycle initially studied proposed in more bydetails M. Mori by S. T.[46] Diver and [ 47further,48]. However, studied in if manymore examplesdetails by involving S. T. Diver ruthenium-catalysis [47,48]. However, have if many been examples involving ruthenium‐catalysis have been described starting from aliphatic including benzylic and propargylic alkynes [49–52], much less data are available from aromatic alkynes in the

Catalysts 2017, 7, 365 3 of 9

Catalysts 2017, 7, 365 3 of 9 Catalysts 2017, 7, 365 3 of 9 described starting from aliphatic including benzylic and propargylic alkynes [49–52], much less data literature. A few mono‐substituted 2‐arylbuta‐1,3‐dienes have been obtained from terminal literature.are available A fromfew aromaticmono‐substituted alkynes in the2‐arylbuta literature.‐1,3‐ Adienes few mono-substituted have been obtained 2-arylbuta-1,3-dienes from terminal arylacetylenes [25,26,53–56], but to the best of our knowledge only one example of synthesis of arylacetyleneshave been obtained [25,26,53–56], from terminal but to arylacetylenes the best of our [25, 26knowledge,53–56], but only to the one best example of our knowledgeof synthesis only of 2,3‐diphenylbuta‐1,3‐diene via ene‐yne cross‐metathesis starting from an internal has been 2,3one‐diphenylbuta example of synthesis‐1,3‐diene of via 2,3-diphenylbuta-1,3-diene ene‐yne cross‐metathesis viastarting ene-yne from cross-metathesis an internal alkyne starting has frombeen reported [57]. reportedan internal [57]. alkyne has been reported [57]. Herein, we report on the application of ruthenium‐catalyzed ene‐yne cross‐metathesis for the Herein, we report on the applicationapplication of ruthenium-catalyzedruthenium‐catalyzed ene-yneene‐yne cross-metathesiscross‐metathesis for the direct preparation of 2,3‐diarylbuta‐1,3‐dienes of type A from ethylene and a variety of internal direct preparation of 2,3-diarylbuta-1,3-dienes2,3‐diarylbuta‐1,3‐dienes of of type A from ethylene and a variety of internal alkynes. We focused on a new preparation of unsymmetrical dienes performed in one step with alkynes. WeWe focusedfocused on on a a new new preparation preparation of unsymmetricalof unsymmetrical dienes dienes performed performed in one in stepone withstep atomwith atom economy from suitably designed internal alkynes. This process competes in terms of productivity atomeconomy economy from suitablyfrom suitably designed designed internal internal alkynes. alkynes. This This process process competes competes in terms in terms of productivity of productivity and and environmental impact with the methods based on palladium‐catalyzed cross‐coupling of andenvironmental environmental impact impact with the with methods the basedmethods on palladium-catalyzedbased on palladium cross-coupling‐catalyzed cross of functionalized‐coupling of functionalized that produce the desired products in moderate yields together with functionalizedalkenes that produce alkenes the that desired produce products the in desired moderate products yields together in moderate with stoichiometric yields together amount with of stoichiometric amount of wastes [39,41]. wastesstoichiometric [39,41]. amount of wastes [39,41].

2. Results and Discussion 2. Results and Discussion The feasibility of the ene-yneene‐yne cross-metathesiscross‐metathesis between 1,2-diphenylacetylene1,2‐diphenylacetylene with ethylene The feasibility of the ene‐yne cross‐metathesis between 1,2‐diphenylacetylene with ethylene was firstfirst evaluated in the presence of the second generation Grubbs (I) and Hoveyda (II) ruthenium was first evaluated in the presence of the second generation Grubbs (I) and Hoveyda (II) ruthenium catalysts (Figure2 2,, Scheme Scheme1 ).1). catalysts (Figure 2, Scheme 1).

Figure 2. Ruthenium catalysts used in the screening experiments. Figure 2. Ruthenium catalysts used in the screening experiments.

Scheme 1. Ene‐yne cross‐metathesis of 1,2‐diphenylacetylene with ethylene. Scheme 1. EneEne-yne‐yne cross cross-metathesis‐metathesis of 1,2 1,2-diphenylacetylene‐diphenylacetylene with ethylene. The first attempts carried out with 1 atm of ethylene in the presence of 2 mol% of Grubbs The first attempts carried out with 1 atm of ethylene in the presence of 2 mol% of Grubbs catalystThe I firstat room attempts temperature carried in out dimethyl with 1 atmcarbonate of ethylene (DMC) in or the dichloromethane presence of 2 mol%(DCM) of were Grubbs not catalyst I at room temperature in dimethyl carbonate (DMC) or dichloromethane (DCM) were not successfulcatalyst I at (Table room 1, temperature entries 1–3). in Increasing dimethyl carbonatethe ethylene (DMC) pressure or dichloromethane to 5 atm and the (DCM) temperature were not to successful (Table 1, entries 1–3). Increasing the ethylene pressure to 5 atm and the temperature to 80successful °C in DMC (Table or1 ,100 entries °C in 1–3). toluene Increasing made the the ene ethylene‐yne cross pressure‐metathesis to 5 atm possible and the but temperature with modest to 80 ◦°C in DMC or 100 ◦°C in toluene made the ene‐yne cross‐metathesis possible but with modest conversion80 C in DMC (Table or 1, 100 entriesC in 4 toluene and 5). Further made the increase ene-yne of reaction cross-metathesis pressure possibleand reaction but time with in modest DMC conversion (Table 1, entries 4 and 5). Further increase of reaction pressure and reaction time in DMC ledconversion to 90% (Tableconversion1, entries of the 4 andalkyne 5). Further(Table 1, increase entry 6). of A reaction similar pressure beneficial and effect reaction of increasing time in led to 90% conversion of the alkyne (Table 1, entry 6). A similar beneficial effect of increasing ethyleneDMC led pressure to 90% conversion from 1 to of 6 the atm alkyne had (Tablebeen observed1, entry 6). during A similar the beneficial ene‐yne cross effect‐metathesis of increasing of ethylene pressure from 1 to 6 atm had been observed during the ene‐yne cross‐metathesis of ethylene with pressure terminal from propargylic 1 to 6 atm acetates had been [47]. observedThese results during indicated the ene-yne that the cross-metathesisene‐yne metathesis of ethylene with terminal propargylic acetates [47]. These results indicated that the ene‐yne metathesis ofethylene 1,2‐diphenylacetylene with terminal propargylic required acetateshigher pressure [47]. These than results the indicatedene‐yne metathesis that the ene-yne of the metathesis terminal of 1,2‐diphenylacetylene required higher pressure than the ene‐yne metathesis of the terminal phenylacetylene,of 1,2-diphenylacetylene which was required carried higher out in pressure short reaction than the time ene-yne under metathesis1 atm of C of2H4 the at 80 terminal °C in phenylacetylene, which was carried out in short reaction time under 1 atm of C2H4◦ at 80 °C in phenylacetylene,toluene with catalyst which I was [26,53–55], carried outand in even short at reaction room timetemperature under 1 atm with of Ca 2bimetallicH4 at 80 C ruthenium in toluene toluene with catalyst I [26,53–55], and even at room temperature with a bimetallic ruthenium withmetathesis catalyst catalyst I [26,53 precursor–55], and [56]. even The at room Hoveyda temperature catalyst with II was a bimetallic then evaluated ruthenium under metathesis various metathesis catalyst precursor [56]. The Hoveyda catalyst II was then evaluated under various experimental conditions. In dimethyl carbonate, the conversion of 1a at 80 °C under 5 atm of C2H4 experimental conditions. In dimethyl carbonate, the conversion of 1a at 80 °C under 5 atm of C2H4 was similar to that obtained with catalyst I under related conditions (Table 1, entries 4 and 7). It was was similar to that obtained with catalyst I under related conditions (Table 1, entries 4 and 7). It was

Catalysts 2017, 7, 365 4 of 9 catalyst precursor [56]. The Hoveyda catalyst II was then evaluated under various experimental ◦ conditions. In dimethyl carbonate, the conversion of 1a at 80 C under 5 atm of C2H4 was similar to that obtained with catalyst I under related conditions (Table1, entries 4 and 7). It was possible to improve the conversion of the alkyne by increasing the initial concentration of the substrate from 0.06 M to 0.3 M (Table1, entries 8–10). It must be noted that in all the experiments performed in DMC solvent, the formation of 1,2-diphenylbuta-1,3-diene 2a’ resulting from hydrovinylation of the alkyne by ethylene was observed as a byproduct in variable amounts. This side reaction might be attributed to the formation of Ru–H species resulting from the reaction of ruthenium species with MeOH arising from DMC decomposition. It is interesting to note that the formation of 2a’ has been reported only once by reaction of alkynes with ethylene and that a ruthenium hydride was assumed to be essential for this catalytic reaction [58]. Such Ru–H species were also previously proposed to be responsible of carbon–carbon double bonds migration during olefin metathesis reactions performed in boiling DMC [59]. Toluene appeared to be a better solvent as the reaction carried out under 3 atm of ethylene at 100 ◦C for 17 h gave full conversion of the alkyne (Table1, entry 11). Not only the conversion of the alkyne was better, but the selectivity in favor of the 2,3-diphenylbuta-1,3-diene was excellent since 2a’ could not be detected. Optimization of the reaction in toluene revealed that 100 ◦C, 17 h were the optimum experimental conditions whereas a higher pressure of ethylene had a negative effect inhibiting the catalytic reaction, and lower catalyst loading led to decreased activity (Table1, entries 12–15). The first generation catalyst III utilized in the conditions of entry 7 led to only 10% conversion [60] and a high proportion of hydrovinylation product 2a’. The conditions reported in entry 11 appeared to be the best to investigate the scope of the reaction focused on the synthesis of unsymmetrical 2,3-diarylbuta-1,3-dienes.

Table 1. Optimization of the ene-yne cross-metathesis of 1,2-diphenylacetylene with ethylene a.

Catalyst Ethylene Conversion c Entry Solvent T (◦C) t (h) (mol%) Pressure (atm) (%) 1 I (2 mol%) 1 DMC 0.01 M 25 4 0 2 I (2 mol%) 1 DCM 0.06 M 25 4 0 3 I (2 mol%) 1 DMC 0.06 M 25 4 5 4 I (2 mol%) 5 DMC 0.06 M 80 17 60 d 5 I (2 mol%) 5 toluene 0.06 M 100 17 64 d 6 I (2 mol%) 7 DMC 0.06 M 80 22 90 d 7 II (2 mol%) 5 DMC 0.06 M 80 24 50 d 8 II (2 mol%) 5 DMC 0.1 M 80 23 94 d 9 II (2 mol%) 5 DMC 0.3 M 90 b 17 92 d 10 II (2 mol%) 3 DMC 0.3 M 90 b 17 95 d 11 II (2 mol%) 3 toluene 0.3 M 100 17 100 (90%) e 12 II (2 mol%) 3 toluene 0.3 M 70 17 67 13 II (2 mol%) 3 toluene 0.3 M 120 8 90 14 II (2 mol%) 25 toluene 0.3 M 100 72 0 15 II (1 mol%) 3 toluene 0.3 M 100 17 80 a Tolane (0.51 mmoles); b DMC boiling point under atmospheric pressure; c Determined by gas chromatography using tetradecane as internal standard; d presence of 1,2-diphenylbuta-1,3-diene 2a’ (up to 15% determined by 1H Nuclear Magnetic Resonance); e (isolated yield).

The unsymmetrical phenylacetylene derivatives 1b–s were prepared according to the Sonogashira method from phenylacetylene and the desired substituted halogenated aryl derivatives in the presence of catalytic amounts of PdCl2(PPh3)2 and CuI (See Supplementary Materials). Several alkynes presenting different electronic and steric properties were prepared in order to evaluate the full potential of the synthetic method. The results of the ene-yne cross-metathesis reactions of these substrates with C2H4 (Scheme2) are gathered in Table2. Catalysts 2017, 7, 365 5 of 9 Catalysts 2017, 7, 365 5 of 9

CatalystsCatalystsCatalystsCatalysts 2017 2017 2017 ,2017 ,7 7, ,365 ,365 7, 7, ,365 365 55 of of 59 95 of of 9 9 Catalysts 2017, 7, 365 5 of 9 CatalystsCatalystsCatalysts 2017 2017 2017, ,7 7, ,365, 3657, 365 55 of of 59 9 of 9 CatalystsCatalystsCatalystsCatalysts 2017 2017 ,2017 20177,, 7365,, ,3657 7 , ,365 365 5 of5 of95 5 9of of 9 9

Scheme 2. EneEne-yne‐yne cross cross-metathesis‐metathesis of unsymmetrical diarylacetylenes. SchemeScheme 2. Ene 2. Ene‐yne‐yne cross cross‐metathesis‐metathesis of unsymmetrical of unsymmetrical diarylacetylenes. diarylacetylenes. SchemeSchemeSchemeScheme 2. 2. Ene Ene 2. 2. ‐Ene yneEne‐yne‐ ‐ynecrossyne cross cross cross‐metathesis‐metathesis‐‐metathesismetathesis of of unsymmetrical unsymmetricalof of unsymmetrical unsymmetrical diarylacetylenes. diarylacetylenes. diarylacetylenes. diarylacetylenes. SchemeSchemeSchemeScheme 2. 2. Ene 2.Ene 2. Ene ‐Eneyne‐yne‐yne‐ crossyne cross cross cross‐metathesis‐metathesis‐metathesis‐metathesis of of unsymmetrical of unsymmetricalof unsymmetrical unsymmetrical diarylacetylenes. diarylacetylenes. diarylacetylenes. diarylacetylenes. The presence Scheme of Scheme an electron electron-donating2. Ene 2. ‐Eneyne‐donating‐ crossyne cross‐metathesis‐ metathesis or ‐ -withdrawingwithdrawing of unsymmetrical of unsymmetrical groups diarylacetylenes. indiarylacetylenes. para-position‐position of one of the aryl TheTheThe The presencepresence presence presence ofof an anof of electronanelectron an electron electron‐‐donatingdonating‐donating‐donating oror ‐ ‐orwithdrawing withdrawingor ‐ ‐withdrawingwithdrawing groupsgroups groups groups inin para parain in para ‐para‐positionposition‐position‐position ofof one oneof of one one ofof the theof of the arylthearyl aryl aryl groupsTheThe Thedid Thepresence presence notpresence presence inhibit of of an ofan of theanelectron electronan electron cross-metathesiscrosselectron‐donating‐‐donatingmetathesis‐donating‐donating or or ‐ or ‐withdrawing with orwithdrawing ‐ ‐withdrawingwithdrawing ethylene groups groups and groups groups the in in para correspondinginpara in para ‐paraposition‐position‐position‐position of of one ofdienes one of one oneof of the of the 2bof the aryl– thearylh aryl were aryl groupsgroupsgroupsgroupsTheThe diddid TheThepresence didpresence didnotnot presencepresence not inhibitnotinhibit ofinhibit inhibitof an ofan ofthethe electron an an electron the crossthecross electronelectron cross cross‐‐‐metathesisdonatingmetathesis‐donating‐metathesis‐‐donatingmetathesisdonating or withorwith ‐ withdrawing ‐ or orwith withdrawingwith ‐ ‐ ethylenewithdrawingethylenewithdrawing ethylene ethylene andand groups groupsand and the groupsthegroups the correspondingtheincorresponding in paracorresponding corresponding inparain para‐paraposition‐position‐‐positionposition dienesdienes of of dienes onedienes ofoneof 2b one2bofone of – –2bthe h 2bh oftheof –werewere –haryl thetheh arylwere were aryl aryl isolatedgroupsgroupsgroupsgroups did didin did highdidnot not not inhibitnot inhibityields inhibit inhibit the afterthe the cross thecross 17–24cross cross‐metathesis‐metathesis‐ metathesis‐hmetathesis (Table with with2, with withentries ethylene ethylene ethylene ethylene 1–7). and and andTotal andthe the the corresponding thecorrespondingconversion corresponding corresponding of dienes thedienes dienes dienesparapara 2b 2b‐ –halogenated2b– h2bh –were were–hh were were isolatedgroupsisolatedisolatedgroupsisolatedgroupsisolatedgroups did in in indid high inhighdid not highdidin not high high notinhibit notyieldsyields yieldsinhibit yields inhibitinhibityields aftertheafter afterthe after crosstheafterthe 17–24cross17–24 17–24 crosscross17–24 ‐17–24metathesis‐ metathesishh‐ ‐ metathesis(Table h (Tablemetathesish h (Table (Table (Table 2,2,with 2 with entries entries,2, 2, entries with with entries ethyleneentries ethylene ethylene1–7).ethylene1–7). 1–7). 1–7). 1–7). andTotalTotal and Total Total and Totalandthe conversiontheconversion correspondingthe conversiontheconversion correspondingconversion correspondingcorresponding ofof theofthe ofof thedienes the parathe paradienes paradienes dienes‐para‐halogenatedhalogenated 2b‐ halogenated‐2b-halogenatedhalogenated– h2b–2b hwere– –werehh werewere derivativesisolatedisolatedisolatedisolated in in high in1i highin –high khigh yields wereyields yields yields obtainedafter after after after 17–24 17–24 17–24 17–24under h h (Table (Tableh h similar(Table (Table 2, 2, entries 2, entries conditions2, entries entries 1–7). 1–7). 1–7). 1–7). Totaland Total Total Totalthe conversion conversion dienesconversion conversion 2i of –ofk the of weretheof the para thepara isolatedpara ‐parahalogenated‐halogenated‐halogenated‐halogenated in 89–90% derivativesisolatedderivativesisolatedderivativesisolatedderivativesisolated in in high 1i 1i in1ihighin–– –k1i k highhigh1ik wereyields–were –werekyieldsk were yieldswereyields obtainedobtained after obtained afterobtained obtained afterafter 17–24 17–24 under under 17–2417–24 under under hunder h(Table similar similar (Tablehh similar (Tablesimilar(Table similar 2, conditions2, conditionsentries 2,entries conditions2,conditions conditions entriesentries 1–7). 1–7). andand 1–7).1–7). Totaland and theTotalthe Total Total the thedienesthedienesconversion conversion dienes dienes conversionconversion 2i2i–– k2ik 2i were–ofwere–k– ofk k thewere wereofweretheof isolatedisolated parathethe paraisolated isolated isolated para‐parahalogenated‐halogenated inin‐‐halogenated halogenated 89–90% 89–90%in in in89–90% 89–90% 89–90% yieldderivativesderivativesderivativesderivatives without 1i 1i– – 1ik knoticeable1i –were were–kk were were obtained obtained obtained obtained dehalogenation. under under under under similar similar similar similar conditionsCompounds conditions conditions conditions and and and2i andthe the and the dienes thedienes dienes 2kdienes 2i are2i– –2ik k2i particularly–were were–kk were were isolated isolated isolated isolated interestingin in 89–90% in89–90% in 89–90% 89–90% for yieldderivativesyieldderivativesyieldderivativesyieldderivatives withoutwithout withoutwithout 1i 1i– noticeableknoticeable –noticeable 1i1i kwere – – noticeablewerekknoticeable werewere obtained obtained dehalogenation. obtaineddehalogenation.obtaineddehalogenation. dehalogenation.dehalogenation. under under underunder similar similar similarsimilar CompoundsCompoundsCompounds conditions CompoundsconditionsCompounds conditionsconditions and2i2i2i and and and 2i andandthe2i the and2k and dienes the2kthe2k dienesare 2k dienesaredienesare2k particularly 2i are are particularlyparticularly2i–k – 2i particularly2i kwereparticularly– –werekk werewere isolated interestingisolated interesting isolatedinterestingisolated interestinginteresting in in 89–90% in89–90%in for 89–90% 89–90%forfor further for for yieldyieldyieldyield withoutwithout without without noticeablenoticeable noticeable noticeable dehalogenation.dehalogenation. dehalogenation. dehalogenation. CompoundsCompounds Compounds Compounds 2i2i and2i and2i and and 2k2k 2k are2kare are areparticularlyparticularly particularly particularly interestinginteresting interesting interesting forfor for for furtheryieldfurthercross-couplingfurtheryieldfurtheryieldfurtheryield without crosswithoutcross without withoutcross cross‐‐coupling‐coupling couplingnoticeable ‐ reactions.couplingnoticeable‐coupling noticeablenoticeable reactions.reactions. reactions. reactions.dehalogenation. The reactions.dehalogenation. dehalogenation.dehalogenation. mixed TheThe The The The mixed phenylmixed mixed mixed mixed Compounds phenylCompoundsphenyl 2-thiophenyl Compounds phenylCompoundsphenyl phenyl 22‐‐thiophenyl thiophenyl 2 2‐2i thiophenyl‐2ithiophenyl and butadiene 2i2iand and and2k butadiene2kbutadiene are2k 2k butadiene arebutadienebutadiene 2l areparticularlyare wasparticularly particularly particularly2l2l isolated waswas2l 2l2l was was was isolatedisolatedinteresting interesting inisolated isolated isolatedinterestinginteresting 60% inin yield 60% in60% infor infor60% 60% afterfor60%for furtherfurtherfurtherfurther cross cross cross cross‐coupling‐coupling‐coupling‐coupling reactions. reactions. reactions. reactions. The The The Themixed mixed mixed mixed phenyl phenyl phenyl phenyl 2 2‐thiophenyl‐ thiophenyl2 2‐thiophenyl‐thiophenyl butadiene butadiene butadiene butadiene 2l 2l was 2l was2l was wasisolated isolated isolated isolated in in 60% in 60%in 60% 60% yieldfurtheryieldcompletefurtheryieldfurtheryieldfurther afterafter cross aftercrossafter conversion completecrosscompletecrosscomplete‐coupling ‐ completecouplingcomplete‐‐couplingcoupling conversion conversion conversion ofreactions. conversionreactions.conversion the reactions.reactions. starting Theofof The of the ofthe Theof Themixed the alkyne themixed thestartingstarting mixed mixed starting starting startingphenyl 1lphenyl phenylalkyne(Tablephenylalkyne alkyne alkyne2alkyne ‐2thiophenyl‐2 thiophenyl 21l,21l‐‐ entrythiophenyl thiophenyl (Table 1l(Table1l (Table(Table(Table 11). butadiene 2, 2,butadiene Substitutionentry butadiene2,entrybutadiene2, entryentry 11). 11).2l 2l 11). was11). 11).Substitution 2lSubstitutionwas2l at was Substitutionwas isolatedSubstitutionSubstitution theisolated isolatedisolatedortho in at atin 60%-position the inatthein60%at at 60% the 60% the the yieldyieldyieldyield afterafter after after completecomplete complete complete conversionconversion conversion conversion ofof theof theof the thestartingstarting starting starting alkynealkyne alkyne alkyne 1l1l (Table1l (Table1l (Table (Table 2,2, entry2, entry2, entry entry 11).11). 11). 11). SubstitutionSubstitution Substitution Substitution atat theat theat the the orthoyieldorthoofyield oneorthoyieldorthoyield‐ ‐positionpositionafter phenylafter‐position‐ positionafterafter complete complete of of of groupcompletecomplete one ofone oneof one one phenylphenylconversion wasphenylconversion phenyl phenylconversionconversion more groupgroup group group group problematic.of of waswas the ofwasof thewas was morethestartingmorethe startingmore more morestartingstarting problematic.problematic. Indeed, problematic.problematic.alkyne problematic.alkyne alkynealkyne with1l 1l Indeed, Indeed,(Table 1l1l(Table the Indeed, Indeed, Indeed,(Table(Tableo -cyano 2, with with2, entry with2, 2,entrywith the theentryentry group 11). the otheo11).‐‐cyano cyano 11).o 11). Substitutiono‐o incyano‐‐Substitutioncyanocyano 1mSubstitution Substitution groupgroup agroup group verygroup inin at 1min1m low at in the in at1m at thea1ma yield1m the the a a a orthoorthoorthoortho‐position‐position‐position‐position of of one of oneof one onephenyl phenyl phenyl phenyl group group group group was was was wasmore more more more problematic. problematic. problematic. problematic. Indeed, Indeed, Indeed, Indeed, with with with with the the the o theo‐cyano‐ cyanoo ‐ocyano‐cyano group group group group in in 1m in 1min 1m a 1ma a a veryorthoveryoforthovery 18%orthoveryortho ‐ lowpositionlow‐position waslow‐ ‐lowposition positionyieldyieldyield yield obtained yieldof of ofofone of ofone18% of18%of18% one onephenyl 18% 18% phenyl whereaswaswas phenylwasphenyl was was obtainedgroupobtained obtainedgroup obtained obtainedgroupgroup no was reactionwas whereaswhereas was wasmore whereas whereasmorewhereas moremore problematic. took noproblematic.no problematic. noproblematic. noreactionreactionno place reaction reaction with Indeed, took tookIndeed, tookIndeed,tookIndeed,took the placeplace with o place place-OMewithplace withwith the withthewith and othethethe ‐ocyano ‐ thecyano otheootheo‐‐-NOcyano‐OMecyano OMe o o‐groupoOMe‐ ‐OMegroupOMe and substratesgroupandgroup andin and oandino ‐1m‐ NO NOin1min oo‐ NO‐1mao21mNO2 ‐ aNO1n 2 a a2, o 2 very low yield of 18% was obtained whereas no reaction took place with the o‐2OMe and o‐NO2 2 veryvery lowlow yieldyield ofof 18%18% waswas obtainedobtained whereaswhereas nono reactionreaction tooktook placeplace withwith thethe oo‐OMe‐OMe andand oo‐NO‐NO2 2 substratessubstratesverysubstratesveryvery low lowlow 1n 1nyield , o yield1n,yieldo (Table ,(Tableo of (Table of of18% 2, 18% 18%2, entries 2, wasentries entries waswas obtained 13 obtained obtained13 and13 and and 14) whereas 14) 14) whereasevenwhereas even even when no when when no no reactionextended reactionreaction extended took reaction tooktook reactionreactionplace placeplace time with time withtimewith or the higher or theorthe highero higher ‐ OMeoo‐ temperaturesOMe‐OMe temperatures and temperatures andand o ‐NO oo‐NO‐ NO2 2 very(Tablesubstratessubstratesverysubstrates substrateslow2, entries lowyield 1n 1n ,yield o,1n o1n (Tableof (Table, 13o, o 18% (Table of(Table and 2,18% 2,was entries 14) entries2, 2, was entries entriesobtained even 13 obtained13 and when 13 and13 and whereasand14) 14) extended whereaseven14) 14)even even even whenno when reactionwhen nowhen reaction extended extendedreaction extended extended took time reactiontook reaction place reaction orreaction place higher withtime time withtime time orthe temperaturesor higher orhigher theoor‐ OMehigher higher o‐ temperaturesOMe temperatures and temperatures temperatures and wereo‐NO o‐ used.2NO 2 wereweresubstratessubstratesweresubstratessubstrates used.used. used. 1nBoth 1nBoth ,1n o ,Both1no (Table , (Tableothe, othe (Table (Table thesteric steric2, 2,steric entries 2, entries 2,hindrance entries entrieshindrance hindrance 13 13 and13 13and and and14) and 14)and 14) the even14) even the theeven potentialeven when potentialwhenpotential when when extended extended catalyst extended extended catalyst reactioninhibition reaction reaction inhibitionreactioninhibition time time bytime time or bycoordination orby higheror higherorcoordination coordinationhigher higher temperatures temperatures temperatures temperatures of theseof of these these substratesBothwereweresubstrateswerewere theused. used. steric used. used.1n Both ,Botho 1n hindrance(Table BothBoth ,othe the (Table thesteric the2,steric entries steric steric2, and hindrance entrieshindrance the hindrance 13hindrance and potential 13 and 14)and and even14)andthe the catalyst even thepotential thewhenpotential potential potentialwhen inhibition extended catalyst extendedcatalyst catalystcatalyst byreaction inhibition inhibition coordination reaction inhibitioninhibition time by time byor coordination by higherbycoordination of or coordination these coordinationhigher temperatureso-substituents temperatures of of these oftheseof thesethese to owere‐substituentswereowere‐weresubstituents used. used. used. used. Both Both to Both Both thetothe the thethe metalthesteric steric metalsteric steric centerhindrance hindrance centerhindrance hindrance might might and and be and and theat bethe the atthepotential potential theoriginpotential potential origin ofcatalyst catalyst theofcatalyst catalyst thelow inhibition lowinhibition reactivity.inhibition inhibition reactivity. by by Limitations by coordination bycoordination Limitationscoordination coordination were of wereof theseof alsoofthese these alsothese wereothe‐osubstituents‐substituentswereo metalo‐ ‐substituentsused.substituents used. center Both to toBothto the mightthe the totheto thestericmetal themetal be metalstericmetal athindrancecenter centercenter the hindrance centercenter origin might mightmight mightandmight ofbe andbe thebe the at beatbe atthepotential low the at atthe theoriginpotential theorigin reactivity. origin originorigin catalyst of of theof catalyst oftheof Limitations the thelow thelowinhibition low low low reactivity. inhibitionreactivity. reactivity. reactivity.reactivity. wereby coordinationLimitations byLimitations also LimitationscoordinationLimitationsLimitations observed were wereof were thesewere withwere ofalso also these also 1qalsoalso – s observedo‐osubstituents‐observedsubstituentsoo‐substituents‐substituents with with to1q to the–to 1qthesto thefor –metalthe smetal forwhichmetal metal whichcenter center center stericcenter stericmight might hindrancemight might hindrancebe be beat beat theat theat( 1qthe originthe ()origin1q ororigin origin) substrateor of of substrate theof theof the lowthe low additional low lowreactivity. additionalreactivity. reactivity. reactivity. coordination Limitations Limitationscoordination Limitations Limitations sitewere were sitewere were(1r also ,also(s1r )also also ,s ) oobservedfor‐observedsubstituentso whichobservedobserved‐substituents with with stericwith with withto 1q 1q 1qthe hindrance –to – –1qs1q smetalthefor –for–ss forwhichmetal forwhich center which (which1q centersteric ) stericsteric ormight stericsteric substrate hindrancemight hindrancehindrance be hindrancehindrance at be the additionalat ( 1q(originthe 1q( 1q) ( ()1q or1q origin)or ) or) substrate of orsubstrateor coordination substrate the substrateofsubstrate lowthe additional lowadditionalreactivity. additional additionaladditional reactivity. site (coordination 1rLimitationscoordination, s coordinationcoordination coordination)Limitations might be weresite site responsible were site site( site1ralso(1r, s (, (1r)salso (1r )1r ,s,s,)s) ) mightobservedobservedmightobservedobserved be withbe responsiblewith with withresponsible 1q 1q –1q s–1q sfor– –fors s for fromwhichfor which fromwhich which the steric steric thesteric stericlack hindrance lackhindrance hindrance ofhindrance ofreactivity. reactivity.( 1q(1q ( )1q( )1qor or ) )substrateorOn orsubstrate substrate Onsubstratethe the contrary,additional additional contrary,additional additional thecoordination coordination thecoordination coordinationarylalkylacetylene arylalkylacetylene site site site site( 1r(1r ,( s1r(,) s1r ), s,s) ) observedmightfrommightobservedmightmight the bebe lack with beresponsibleberesponsibleresponsible with of1qresponsibleresponsible reactivity.– s1q for–s whichforfromfrom Onwhichfromfrom stericthe thethethe thesteric the contrary, lack lackhindrancelack lack lack hindranceof of of theofreactivity. ofreactivity. reactivity. (reactivity.1q arylalkylacetylenereactivity. )( 1qor ) substrate orOnOn Onsubstrate On Onthethe the theadditional thecontrary,contrary, hex-1-yn-1-ylbenzene additionalcontrary,contrary,contrary, coordinationthethe thecoordinationthe thearylalkylacetylenearylalkylacetylene arylalkylacetylenearylalkylacetylene site1p site(led1r, s( to)1r , fulls) hexmightmighthex‐might1might‐yn ‐1 be‐‐ynbe1 ‐beylbenzene ‐beresponsible1responsible ‐ ylbenzeneresponsibleresponsible 1p from1pledfrom from ledfromto the fulltothe the full the conversionlacklack conversionlacklack ofof of reactivity.ofreactivity. and reactivity.reactivity. and an anexcellent On Onexcellent On On thethe 97%the the contrary, contrary,97% contrary,isolatedcontrary, isolated the yieldthe the theyield arylalkylacetylenearylalkylacetylene of arylalkylacetylenearylalkylacetylene 2pof , 2pa class, a class of of mighthexconversionhexmight‐hexhex1‐1‐ yn‐‐ynbe‐11‐‐ 1 ‐yn1yn1‐‐beresponsibleylbenzene‐ andylbenzene‐ylbenzene‐1 1‐‐ylbenzeneresponsibleylbenzene an excellent 1p 1pfrom led 1p 1pledfrom 97% led to led totothe full to fullfullto isolated the lackfullconversionfull conversion conversion lack conversionconversionof yield reactivity.of and ofreactivity.and and 2p and andan an, a an excellent anOn classexcellentan excellent excellent excellentOnthe of 1,3-dienesthe97% contrary,97% 97% 97% 97%contrary,isolated isolated isolated isolated scarcelythe yield yield the arylalkylacetylene yieldyieldyield of reported arylalkylacetyleneof 2p of2pof, ,2p a 2pa class , class, employing, a aa class classclass of of of ofof 1,3hexhex‐hexdienes‐hex1‐‐1yn‐1yn‐1‐‐yn‐ 1‐scarcelyyn‐1ylbenzene‐1ylbenzene‐1‐ylbenzene‐ylbenzene reported 1p 1p 1p led 1pled employing led toled to fullto fullto full fullconversion conversion olefinconversion conversion metathesis and and and andan an an excellent an[57].excellent excellent excellent 97% 97% 97% 97% isolated isolated isolated isolated yield yield yield yield of of 2pof of2p ,2p ,a2p a,class ,aclass a class class of of of of hex1,31,3‐‐hex1,3dienes1‐‐yndienes‐‐dienes1‐‐1yn ‐ scarcelyscarcelyylbenzene‐ 1scarcely ‐scarcelyylbenzene reported reported reported1p reported led1p employingledto employing employing fullemploying to fullconversion conversionolefin olefin olefin olefin metathesis and metathesismetathesis metathesis andan excellentan [57]. excellent [57]. [57]. 97% 97% isolated isolated yield yield of 2p of, a2p class, a class of of olefin1,31,3‐1,3dienes‐1,3dienes‐ metathesisdienes‐dienes scarcely scarcely scarcely scarcely [ 57reported reported]. reported reported employing employing employing employing olefin olefin olefin olefin metathesis metathesis metathesis metathesis [57]. [57]. [57]. [57]. 1,31,3‐dienes1,31,3‐dienes‐‐dienesdienes scarcely scarcely scarcelyscarcely reported reported reportedreported employing employing employingemploying olefin olefin olefinolefin metathesis metathesis metathesismetathesis [57]. [57]. [57].[57]. a a TableTable 2. Ene 2. Ene‐yne‐yne cross cross‐metathesis‐metathesis of unsymmetrical of unsymmetrical diarylacetylenes diarylacetylenes with with ethylene ethylene a. .a TableTable 2. Ene 2. ‐Eneyne‐ ynecross cross‐metathesis‐metathesis of unsymmetrical of unsymmetrical diarylacetylenes diarylacetylenes with with ethylene ethylene .a a.aa TableTableTable 2.2. Ene-yneEne 2. Ene‐yne‐yne cross cross-metathesiscross cross‐‐metathesismetathesis‐metathesis of of unsymmetrical of unsymmetrical unsymmetrical diarylacetylenes diarylacetylenesdiarylacetylenes diarylacetylenes with with withwith ethylene ethylene ethyleneethylenea . .. TableTable 2. Ene 2. Ene‐yne‐yne cross cross‐metathesis‐metathesis of unsymmetrical of unsymmetrical diarylacetylenes diarylacetylenes with with ethylene ethylene .a a.a TableTableTableTable 2. 2.Ene Ene 2.2. ‐ EneyneEne‐yne‐ ‐crossyneyne cross crosscross‐metathesis‐metathesis‐‐metathesismetathesis of of unsymmetrical ofunsymmetricalof unsymmetricalunsymmetrical diarylacetylenes diarylacetylenes diarylacetylenesdiarylacetylenes with with with withethylene ethylene ethyleneethylene a. . a..

ConversionConversionConversionConversionConversion c EntryEntryEntry SubstrateSubstrate Substrate t (h)t (h)t (h) ConversionConversionb ProductProductProduct YieldYield Yield (%) (%)(%) cc c c EntryEntry SubstrateSubstrate t (h)t (h) ConversionConversionb b ProductProduct YieldYield (%) (%) c c EntryEntry SubstrateSubstrate t (h)t (h) Conversion(%)ConversionConversion(%)(%) b b ProductProduct YieldYield (%) (%)c c EntryEntry SubstrateSubstrate t (h)t (h) ConversionConversion(%) (%) b b ProductProduct YieldYield (%) (%)c c c EntryEntryEntry SubstrateSubstrateSubstrate t (h)tt (h) (h) (%)(%)b b ProductProductProduct YieldYieldYield (%) (%) c(%) c EntryEntry SubstrateSubstrate t (h)t (h) (%)(%)(%) b b b ProductProduct YieldYield (%) (%) (%)(%) (%)b(%) b 1 11 1b 1b1b 24 24 24100100 100 2b 2b 91 91 11 11 1b1b 1b1b 2424 2424 100100 100100 2b2b 2b2b 9191 9191 1 1 11 1b 1b 1b 1b 242424 24 24 100100100100 100 2b2b 2b 2b 9191 91 9191 1 1 1b 1b 24 24 100 100 2b 2b 91 91

2 2 1c 1c 17 17 100100 2c 2c 98 98 22 22 1c1c 1c 1c1c 1717 171717 100100 100 100100 2c2c2c 2c2c 9898 98 9898 2 2 22 1c 1c 1c 1c 171717 17 17 100100100100 100 2c2c 2c 2c 9898 98 9898 2 2 1c 1c 17 17 100 100 2c 2c 98 98

OO OO 3 3 O O O O 1d 1d 17 17 100100 2d 2d 99 99 3 3 O O O1d 1d 17 17 100 100 2d 2d 99 99 3 33 OO O O1d1d 1d 17 1717 100 100100 2d2d 2d 9999 99 3 O OO 1d 17 100 2d 99 3 3 33 O OO 1d1d 1d 171717 17 100100100100 2d2d 2d 9999 9999 3 3 O O O1d 1d 17 17 100 100 2d 2d 99 99

4 4 1e 1e 17 17 100100 2e 2e 91 91 4 4 1e 1e 17 17 100 100 2e 2e 91 91 44 444 1e1e 1e1e 1e 1717 17 1717 100100 100 100 2e2e2e 2e 2e 9191 9191 91 44 4 44 1e 1e 1e 1e 171717 17 17 100100100 100100 2e2e 2e 2e 9191 91 9191

55 55 1f1f 1f1f 1717 1717 100100100 100 2f2f 2f2f 9999 9999 55 55 1f1f 1f1f 1717 17 17 100100100 100 2f2f 2f2f 9999 99 99 55 5 55 1f 1f 1f 1f 1f 171717 17 17 17 100100100 100 100100 2f 2f 2f2f 9999 9999 9999

6 6 1g 1g 24 24 100100 2g 2g 97 97 66 66 1g1g 1g1g 2424 2424 100100 100100 2g2g 2g2g 9797 9797 6 6 66 1g 1g 1g 1g 2424 24 24 100100100 100 2g2g 2g 2g 9797 97 97 66 6 1g 1g 1g1g 2424 24 24 100100 100 100 2g 2g2g 97 979797

7 7 1h 1h 24 24 92 92 2h 2h 92 92 77 77 1h1h 1h1h 2424 2424 9292 9292 2h2h 2h2h 9292 9292 7 7 77 1h 1h 1h 1h 2424 24 24 9292 92 92 2h2h 2h 2h 9292 92 92 77 7 1h 1h 1h 2424 24 92 9292 2h 2h2h 92 9292

8 8 1i 1i 17 17 100100 2i 2i 90 90 88 88 1i1i 1i1i 1717 1717 100100 100100 2i2i 2i2i 9090 9090 8 8 88 1i1i 1i 1i 1717 17 17 100100100 100 2i2i 2i 2i 9090 90 90 8 8 1i 1i 17 17 100 100 2i 2i 90 90 8 1i 17 100 2i 90

CatalystsCatalysts 2017, 72017, 365, 7, 365 5 of 9 5 of 9 CatalystsCatalysts 2017, 72017, 365, 7, 365 5 of 9 5 of 9

SchemeScheme 2. Ene 2.‐yne Ene cross‐yne ‐crossmetathesis‐metathesis of unsymmetrical of unsymmetrical diarylacetylenes. diarylacetylenes. SchemeScheme 2. Ene 2.‐yne Ene cross‐yne ‐crossmetathesis‐metathesis of unsymmetrical of unsymmetrical diarylacetylenes. diarylacetylenes.

The presenceThe presence of an of electron an electron‐donating‐donating or ‐withdrawing or ‐withdrawing groups groups in para in‐ paraposition‐position of one of ofone the of aryl the aryl The presenceThe presence of an of electron an electron‐donating‐donating or ‐withdrawing or ‐withdrawing groups groups in para in‐ positionpara‐position of one of of one the of aryl the aryl groupsgroups did notdid inhibitnot inhibit the cross the cross‐metathesis‐metathesis with withethylene ethylene and theand corresponding the corresponding dienes dienes 2b–h 2b were–h were groupsgroups did not did inhibit not inhibit the cross the cross‐metathesis‐metathesis with withethylene ethylene and theand corresponding the corresponding dienes dienes 2b–h 2b were–h were isolatedisolated in high in highyields yields after after17–24 17–24 h (Table h (Table 2, entries 2, entries 1–7). 1–7). Total Total conversion conversion of the of para the ‐parahalogenated‐halogenated isolatedisolated in high in highyields yields after after17–24 17–24 h (Table h (Table 2, entries 2, entries 1–7). 1–7).Total Total conversion conversion of the of para the‐ halogenatedpara‐halogenated derivativesderivatives 1i–k 1iwere–k were obtained obtained under under similar similar conditions conditions and theand dienes the dienes 2i–k 2iwere–k were isolated isolated in 89–90% in 89–90% derivativesderivatives 1i–k 1iwere–k were obtained obtained under under similar similar conditions conditions and the and dienes the dienes 2i–k 2iwere–k were isolated isolated in 89–90% in 89–90% yieldyield without without noticeable noticeable dehalogenation. dehalogenation. Compounds Compounds 2i and 2i and2k are 2k particularlyare particularly interesting interesting for for yieldyield without without noticeable noticeable dehalogenation. dehalogenation. Compounds Compounds 2i and 2i and2k are 2k particularlyare particularly interesting interesting for for furtherfurther cross cross‐coupling‐coupling reactions. reactions. The mixedThe mixed phenyl phenyl 2‐thiophenyl 2‐thiophenyl butadiene butadiene 2l was 2l wasisolated isolated in 60% in 60% furtherfurther cross cross‐coupling‐coupling reactions. reactions. The mixedThe mixed phenyl phenyl 2‐thiophenyl 2‐thiophenyl butadiene butadiene 2l was 2l isolatedwas isolated in 60% in 60% yieldyield after aftercomplete complete conversion conversion of the of startingthe starting alkyne alkyne 1l (Table 1l (Table 2, entry 2, entry 11). Substitution11). Substitution at the at the yieldyield after aftercomplete complete conversion conversion of the of startingthe starting alkyne alkyne 1l (Table 1l (Table 2, entry 2, entry 11). Substitution11). Substitution at the at the orthoortho‐position‐position of one of phenylone phenyl group group was wasmore more problematic. problematic. Indeed, Indeed, with withthe o the‐cyano o‐cyano group group in 1m in a 1m a ortho‐orthoposition‐position of one of phenylone phenyl group group was morewas more problematic. problematic. Indeed, Indeed, with withthe o ‐thecyano o‐cyano group group in 1m in a 1m a very verylow lowyield yield of 18% of 18%was wasobtained obtained whereas whereas no reaction no reaction took tookplace place with withthe othe‐OMe o‐OMe and ando‐NO o2‐ NO2 very verylow yieldlow yield of 18% of 18%was wasobtained obtained whereas whereas no reaction no reaction took tookplace place with withthe othe‐OMe o‐OMe and oand‐NO o2‐ NO2 substratessubstrates 1n,o 1n(Table,o (Table 2, entries 2, entries 13 and 13 14)and even 14) even when when extended extended reaction reaction time timeor higher or higher temperatures temperatures substratessubstrates 1n,o (Table1n,o (Table 2, entries 2, entries 13 and 13 14) and even 14) evenwhen when extended extended reaction reaction time timeor higher or higher temperatures temperatures werewere used. used. Both Both the stericthe steric hindrance hindrance and theand potentialthe potential catalyst catalyst inhibition inhibition by coordination by coordination of these of these werewere used. used. Both Boththe steric the steric hindrance hindrance and theand potential the potential catalyst catalyst inhibition inhibition by coordination by coordination of these of these o‐substituentso‐substituents to the to metal the metal center center might might be at be the at origin the origin of the of low the reactivity.low reactivity. Limitations Limitations were were also also o‐substituentso‐substituents to the to metal the metal center center might might be at bethe at origin the origin of the of low the reactivity.low reactivity. Limitations Limitations were were also also observedobserved with with1q–s 1q for–s which for which steric steric hindrance hindrance (1q) (or1q substrate) or substrate additional additional coordination coordination site (site1r,s )( 1r,s) observedobserved with with1q–s 1qfor– swhich for which steric steric hindrance hindrance (1q) or(1q substrate) or substrate additional additional coordination coordination site (site1r,s )( 1r,s) mightmight be responsiblebe responsible from from the thelack lackof reactivity.of reactivity. On Onthe thecontrary, contrary, the thearylalkylacetylene arylalkylacetylene mightmight be responsiblebe responsible from fromthe lackthe lackof reactivity.of reactivity. On theOn contrary,the contrary, the arylalkylacetylenethe arylalkylacetylene hex‐1hex‐yn‐‐11‐‐ynylbenzene‐1‐ylbenzene 1p led 1p to led full to conversionfull conversion and anand excellent an excellent 97% 97%isolated isolated yield yield of 2p of, a 2p class, a class of of hex‐1hex‐yn‐‐11‐‐ynylbenzene‐1‐ylbenzene 1p led 1p to led full to conversion full conversion and anand excellent an excellent 97% isolated97% isolated yield yield of 2p of, a 2p class, a classof of 1,3‐dienes1,3‐dienes scarcely scarcely reported reported employing employing olefin olefin metathesis metathesis [57]. [57]. 1,3‐dienes1,3‐dienes scarcely scarcely reported reported employing employing olefin olefin metathesis metathesis [57]. [57].

TableTable 2. Ene 2.‐yne Ene cross‐yne ‐crossmetathesis‐metathesis of unsymmetrical of unsymmetrical diarylacetylenes diarylacetylenes with withethylene ethylene a. a. TableTable 2. Ene 2.‐yne Ene cross‐yne ‐crossmetathesis‐metathesis of unsymmetrical of unsymmetrical diarylacetylenes diarylacetylenes with ethylenewith ethylene a. a.

ConversionConversion EntryEntry SubstrateSubstrate t (h) t (h)Conversion Conversion ProductProduct YieldYield (%) c(%) c EntryEntry SubstrateSubstrate t (h) t (h) (%) b(%) b ProductProduct YieldYield (%) c (%) c (%) b(%) b

1 11 1b 1b1b 24 2424 100 100100 2b 2b2b 91 9191 1 1b 24 100 2b 91

2 2 1c 1c1c 17 17 100 100 2c 2c2c 98 98 2 2 1c 17 17 100 100 2c 98 98

O O 3 33 O O O 1dO 1d1d 17 1717 100 100100 2d 2d2d 99 9999 3 O 1dO 17 100 2d 99

4 4 1e 1e 17 17 100 100 2e 2e 91 91 4 4 1e 1e 17 17 100 100 2e 2e 91 91 Catalysts 2017, 7, 365 6 of 9

5 5 1f 1f 17 17 100 100 2f 2f 99 99 5 5 1f 1f 17 17 Table100 2. Cont.100 2f 2f 99 99

1g Conversion 2g c 6 Entry6 Substrate 1g1g 24 24t (h) 100 100b Product2g2g Yield 97 (%)97 6 6 1g 24 24 100(%) 100 2g 97 97

7 77 1h 1h1h1h 24 2424 92 9292 2h2h 2h2h 9292 92 7 7 1h 24 24 92 92 2h 92 92

8 8 1i 1i 17 17 100 100 2i 2i 90 90 Catalysts8 Catalysts 201788 , 7 ,2017 365 , 7, 365 1i 1i1i 17 1717 100 100100 2i2i 2i 90906 of90 9 6 of 9 CatalystsCatalystsCatalystsCatalysts 2017 2017, 7,2017 ,7 3652017, 365, 7, , 7365, 365 6 6of of 9 96 of6 of9 9 CatalystsCatalysts 2017, 7 20172017, 365,, 77,, 365365 6 of 9 66 ofof 99 CatalystsCatalystsCatalysts 2017 2017, , 7 20177, ,365 365, 7 , 365 66 of of 9 9 6 of 9 CatalystsCatalystsCatalystsCatalysts 2017 2017, ,72017 20177, ,365 365, , 7 7 , ,365 365 66 of of 9 9 6 6 of of 9 9

9 999 1j 1j1j1j22 222222 100 100100100 2j2j 2j2j 92 92 9292 9 9 1j 1j 22 22 100 100 2j 2j 92 92 9 9 1j 1j 22 22 100 100 2j 2j 92 92 99 9 1j 1j 1j 2222 22 100100 100 2j2j 2j 9292 92 9 9 1j 1j 22 22 100 100 2j 2j 92 92

10 101010 1k 1k1k1k17 171717 100 100100100 2k2k 2k2k 91 91 9191 10 10 1k 1k 17 17 100 100 2k 2k 91 91 10 10 1k 1k17 17 100 100 2k 2k 91 91 1010 10 1k 1k 1k17 17 17 100100 100 2k 2k 2k 9191 91 10 10 1k 1k 17 17 100 100 2k 2k 91 91

11 1111 1l 1l1l27 2727 100 100100 2l 2l2l 60 6060 11 11 11 1l 1l 27 27 27100 100 100 2l2l 2l 60 6060 11 11 1l 1l 27 27 100 100 2l 2l 60 60 1111 11 1l1l 1l 2727 27 100100 100 2l2l 2l 6060 60 11 11 1l 1l 27 27 100 100 2l 2l 60 60

12 12 1m 1m48 48 40 40 2m 2m 18 18 12 1212 1m 1m1m 48 4848 40 4040 2m 2m2m 18 1818 12 12 12 1m 1m1m48 48 4840 40 2m2m 2m 18 1818 1212 12 1m1m 1m48 48 48 4040 40 2m 2m 2m 1818 18 1212 1212 1m1m 1m1m48 48 4848 4040 4040 2m2m 2m2m 1818 1818

13 13 1n 1n24 24 0 0 2n 2n 0 0 13 1313 1n 1n1n 24 2424 0 0 0 2n 2n2n 0 0 0 13 13 1n 1n24 24 0 0 2n 2n 0 0 1313 13 13 1n 1n 1n1n24 24 24 2400 0 2n 2n 2n 00 0 0 1313 1313 1n1n 1n1n 24 24 2424 00 00 2n2n 2n2n 00 00

14 14 1o 1o24 24 0 0 2o 2o 0 0 1414 1414 1o1o 1o1o 2424 2424 00 0 0 2o2o 2o2o 00 0 0 14 14 1o 1o24 24 0 0 2o 2o 0 0 1414 14 14 1o 1o 1o1o24 24 24 2400 0 2o 2o 2o 00 0 0 14 1414 1o 1o1o 24 2424 0 00 2o 2o2o 0 00

15 1515 1p 1p1p24 2424 100 100100 2p 2p2p 97 9797 15 15 1p 1p 24 24 100 100 2p 2p 97 97 15 15 1p 1p24 24 100 100 2p 2p 97 97 1515 15 15 1p1p 1p1p24 24 24 24100100 100 2p2p 2p 9797 9797 15 15 1p 1p 24 24 100 100 2p 2p 97 97

16 16 1q 1q17–48 17–48 10 10 2q 2q 0 0 1616 1616 1q1q 1q17–481q17–48 17–48 17–48 1010 1010 2q2q 2q2q 00 0 0 16 16 1q 1q17–48 17–48 10 10 2q 2q 0 0 1616 16 16 1q1q 1q1q17–4817–48 17–48 17–48 1010 10 2q2q 2q 00 0 0 16 1616 1q 1q1q17–48 17–4817–48 10 1010 2q 2q2q 0 00

17 17 1r 1r24 24 0 0 2r 2r 0 0 1717 1717 1r1r 1r1r 2424 2424 00 0 0 2r2r 2r2r 00 0 0 17 17 1r 1r 24 24 0 0 2r 2r 0 0 1717 17 1r1r 1r 2424 24 00 0 2r 2r 2r 00 0 1717 1717 17 1r1r 1r1r 24 24 2424 2400 00 2r2r2r 2r2r 00 0 00

18 18 1s 17–481s 17–48 0 0 2s 2s 0 0 1818 1818 1s 1s 1s17–481s17–48 17–48 17–48 00 0 0 2s2s 2s2s 00 0 0 18 18 1s 1s17–48 17–48 0 0 2s 2s 0 0 1818 18 1s1s 1s17–4817–48 17–48 00 0 2s2s 2s 00 0 18 a18 18 a 1s 1s17–48 17–48 17–48 0 00 2s2s 2s 0 0 0 a Reactiona conditions: alkyne (0.5 mmol), catalyst II (2 mol%), C2H4 (3 2atm),4 temperature 100 °C, a a ReactionReaction conditions:conditions: alkynealkyne (0.5(0.5 mmol),mmol), catalystcatalyst IIII (2(2 mol%),mol%),2 4 CC2HH4 (3(3 atm),atm), temperaturetemperature 100100 °C,°C, a Reaction Reactiona Reaction conditions: conditions: conditions: alkyne alkyne alkyne (0.5 (0.5 mmol), (0.5mmol), mmol), catalyst catalyst catalyst II II (2 (2 mol%),II mol%), (2 mol%), C C2HH4 C(3 2(3H atm), 4atm), (3 atm),temperature temperature temperature 100 100 °C, 100°C, °C, a Reactiona Reaction conditions: conditions:b alkyneb alkyne (0.5 mmol), (0.5 mmol), catalyst catalyst II (2 mol%),II (2 mol%), C2H4 C(322 Hatm),44 (3 atm),temperature temperature 100 °C, 100 °C, aa tolueneReactiona Reaction (2 conditions: mL). conditions: b Conversion alkyneb alkyne (0.5 detemined mmol), (0.5 mmol), catalyst by Gascatalyst II Chromatography(2 mol%),II (2 mol%), C2H4 C (3analysis2 Hatm),4 (3 atm),temperature with temperature tetradecane 100 °C, 100as °C, aa ReactionReactiona tolueneReactiontoluene conditions:conditions: (2 (2conditions:b mL).mL). b alkyne alkyne ConversionConversion alkyne (0.5(0.5 mmol), mmol),(0.5 detemineddetemined mmol), catalystcatalyst catalyst by by IIII Gas(2Gas(2 mol%),IImol%), ChromatographyChromatography(2 mol%), CC2HH 4 C (3(32 H atm),atm),4 (3 analysisanalysis atm), temperaturetemperature temperature withwith◦ tetradecane tetradecane100100 °C, °C,100 °C, asas atoluene toluene ReactionReactionatoluenea Reaction (2 (2 conditions:mL). conditions: mL).(2 mL).conditions: b Conversion Conversion alkyneb alkyneConversion alkyne (0.5(0.5detemined detemined mmol), mmol), (0.5detemined mmol), catalystby catalystby Gas Gasbycatalyst IIChromatography GasIIChromatography (2(2 mol%),ChromatographyIImol%), (2 mol%), CC2HH4 analysis C(3(32analysis2 H atm),4atm), 4 analysis(3 atm), temperaturewith temperaturewith withtemperaturetetradecane tetradecane tetradecane 100100 °C, °C,as 100as °C,as toluene Reaction tolueneReaction (2 conditions:mL). (2 conditions: conditions: mL).b Conversionc balkyne Conversion alkyne alkyne (0.5 (0.5detemined mmol), mmol),(0.5 detemined mmol), catalyst catalystby Gascatalyst by II II (2 ChromatographyGas mol%),(2 II mol%),Chromatography (2 C mol%),2H 4C(3H atm), C(3analysisH atm), temperature (3analysis atm), temperaturewith temperature 100withtetradecaneC, tetradecane toluene100 °C, 100as (2 mL);°C, as toluenetoluene (2 mL). (2 mL).bb Conversion b Conversioncc detemined detemined by Gas by ChromatographyGas Chromatography analysis analysis with withtetradecane tetradecane as as toluenetolueneinternalbtolueneinternal (2 (2standard; mL).mL). (2 standard; mL).bb c ConversioncConversion Isolated bc Conversion Isolated yield. detemineddetemined yield. detemined byby GasGas by ChromatographyGasChromatography Chromatography analysisanalysis analysis withwith withtetradecanetetradecane tetradecanec asas as toluenetolueneinternaltolueneConversioninternal (2 (2standard; mL).mL). (2 standard; mL).b detemined c ConversionConversion Isolated b Conversion Isolated by yield. Gas detemineddetemined Chromatography yield. detemined byby GasGas by analysis ChromatographyGasChromatography withChromatography tetradecane analysisanalysis as internal analysis withwith standard; withtetradecanetetradecane tetradecaneIsolated asas yield. as tolueneinternalinternaltolueneinternal standard;(2standard; mL). standard;(2 mL). c Conversion IsolatedIsolated c cConversionIsolated yield. detemined yield. detemined by Gas by ChromatographyGas Chromatography analysis analysis with withtetradecane tetradecane as as internalinternalinternal standard; standard;standard; c cIsolated c IsolatedIsolated yield. yield. internalinternalinternal standard; standard; standard; c cIsolated Isolated c Isolated yield. yield. yield. internalinternalinternalinternal standard; standard; standard; standard; c Isolated Isolated c Isolated Isolated yield. yield. yield. yield. 3. Conclusions3. Conclusions 3.3. Conclusions Conclusions3.3. Conclusions Conclusions 3. Conclusions3. Conclusions 3.3. Conclusions Conclusions3. Conclusions 3. Conclusions3.3.We Conclusions Conclusions haveWeWe haveshownhaveshown shownshown thatthat 2,3 thatthat‐‐diarybuta 2,32,3‐‐diarybutadiarybuta‐‐1,3‐‐dienes‐‐1,31,3‐‐dienesdienes could could could be prepared bebe preparedprepared fromfrom fromfromdiarylacetylenes diarylacetylenesdiarylacetylenes using using using We haveWe havehave shownshown shownshown thatthat thatthat2,3‐‐diarybuta 2,3-diarybuta-1,3-dienes2,3‐diarybuta‐‐1,3‐‐dienes‐1,3‐dienes couldcould could be prepared be prepared fromfrom from diarylacetylenes diarylacetylenes using using ene‐Weyneene have Wecross‐yne have shown‐crossmetathesis shownshown‐ metathesisthat 2,3thatthatwith‐diarybuta 2,3 withHoveyda‐‐diarybuta Hoveyda‐1,3 second‐dienes‐‐1,3 ‐second‐dienes generationcould generationcould be prepared catalyst.be prepared catalyst. fromThe from fromreactiondiarylacetylenesThe diarylacetylenesreaction requires requires usinga low using a low eneene‐yne‐eneene-yneWeyneWeene ‐ crossynehaveWehave‐Wecrossyne have cross-metathesiscross ‐have shownmetathesis‐crossshownmetathesis ‐ shownmetathesisshown‐metathesis thatthat with that 2,3thatwith2,3‐ ‐diarybuta with diarybuta2,3 Hoveyda2,3 withHoveyda‐‐diarybutadiarybuta Hoveyda Hoveyda‐‐1,3 1,3second second‐‐dienes‐dienes‐1,3 1,3 second ‐second‐ dienesdienesgeneration generation couldcould generation generationcouldcould bebe preparedcatalyst. prepared catalyst.bebe prepared catalyst.prepared catalyst. The fromThefrom The reactionfrom The fromreaction diarylacetylenesThediarylacetylenes reaction reaction diarylacetylenesreactiondiarylacetylenes requires requires requires requires requires a usingausing low low using a using a low low ene‐yneWeene ‐‐havecrossyne cross‐shownmetathesis‐‐metathesis that with2,3‐ diarybuta withHoveyda Hoveyda‐1,3 second‐dienes secondsecond generation could generation be preparedcatalyst. catalyst. Thefrom reactionThe diarylacetylenes reactionreaction requires requiresrequires ausing low a lowlow eneeneethylene‐‐yneyneeneethyleneethylene ‐ crossyne cross pressure cross‐‐metathesis metathesispressurepressure ‐ ofmetathesis 3 atm ofof with with 33 and atmatm with HoveydaHoveyda a andand temperaturetemperature Hoveyda aa temperaturetemperature secondsecond second of generation generation100 ofof °C.generation°C. 100100 ◦Toluene °C.°C. catalyst.catalyst. TolueneToluene catalyst. was TheThe foundfound waswas reactionThereaction foundfound toto reaction be torequirestothetherequires bebe best requires thethe solvent solvent abestbesta lowlow solventasolvent low eneethylene‐yneeneethyleneene ‐ ‐ ynecrosspressureyne cross‐pressurecross metathesis ‐of‐metathesismetathesis 3 atmof 3 with andatm withwith Hoveydaaand temperaturetemperature HoveydaHoveyda a temperature second second ofsecond 100generation of °C. °C.generation100 generation Toluene °C.C. catalyst. Toluene catalyst.wascatalyst. The wasfoundfound ThereactionThe found toto reaction reactionbe to thetherequires be best the requiresrequires bestsolventsolvent a low solvent aa lowlow ethyleneallowingethyleneallowing pressure the pressureselective the of selective3 atmof formation 3 andatm formation aand temperature of a thetemperaturetemperature of desired the of desired 100 products of °C. 100 products Toluene °C.°C. whereas Toluene waswhereas in foundwas a greenerfoundinfound to a begreener to to thesolvent be best thethe solvent solventbestsuch solvent solvent suchas as allowingethyleneethyleneallowingethyleneallowingethyleneallowing pressure thepressurethe pressure selectivepressurethe selective the ofselective of selective 33 ofatmof formationatmformation 33 atmandatmformationand formation andaanda temperature oftemperatureof aa the temperaturethetemperatureof of desiredthe desired the desired ofofdesired 100 products100 products ofof °C. 100°C.100products products Toluene Toluene°C.°C. whereaswhereas TolueneToluene whereas whereaswaswas in in was found wasfound a a in greener foundgreenerinfound a to toa greener begreenerbe toto solvent thethe solvent bebe best solventbestthe thesolvent such best solventbestsuchsolvent such solvent solvent assuchas as as ethyleneallowingallowing pressurethe selectivethethe ofselectiveselective 3 atmformation and formationformation a temperatureof the of desiredthethe desiredof 100products °C. products Toluene whereas whereas was in found a iningreener ato greener be solventthe best solventsolvent suchsolvent suchsuchas as allowingallowingdimethylallowingdimethyldimethyl the thecarbonate selectiveselectivethe carbonatecarbonate selective thethe formation formation formationformation thethe formation formationformation of ofof thehydrovinylationthe of of of desireddesired the hydrovinylationhydrovinylation desired productsproducts byproductsproducts byproductswhereasbyproductswhereas whereas was inin observed. was wasaa ingreenergreener observed.observed.a greener However, solventsolvent However,However, solvent suchthisthissuch sidesidesuch thisasthisas sidesideas allowingdimethylallowingdimethylallowing carbonatethecarbonate selectivecarbonatethe the selectiveselective thethe formationformationformation the formationformation formation ofof hydrovinylationthe of of hydrovinylation desiredthethe desireddesired products byproducts productsproducts byproducts whereas whereas whereas was in observed.was a in ingreenerobserved. aa greenergreener However, solvent However, solventsolvent thisthissuch sideside this such suchas side asas dimethylreactiondimethylreaction carbonatepresents carbonate presents a thesynthetic formationa thethe synthetic formationformation interest of interest hydrovinylation and of hydrovinylation will and be will investigated be byproducts investigated byproducts in wasmore in observed.was moredetails. observed. details. From However, From However,unsymmetrical unsymmetricalthis side thisthis sideside reactiondimethyldimethylreactionreactiondimethylreaction presents carbonate presentscarbonate presents carbonatepresents a a synthetic the syntheticthe a formation a synthetic formationthe synthetic formationinterest interest interestof ofinterest hydrovinylation andhydrovinylation and of will andhydrovinylation will and be will be will investigated investigated be be investigatedbyproducts investigatedbyproducts investigated byproducts in in more was more was in in moremore observed. details.was observed.moredetails. details.details.observed. details. From From However, However, From unsymmetricalFrom unsymmetricalHowever, unsymmetrical unsymmetricalthis this side sidethis side dimethylreactiondimethylreactionreaction presents carbonate presentscarbonate a syntheticthe a formation syntheticthesynthetic formation interest interestofinterest hydrovinylationand of hydrovinylation willand bewill investigated be byproducts investigatedinvestigated byproducts in more was inin more wasobserved.details. observed. details. From However, From unsymmetricalHowever, unsymmetrical this sidethis side reactionreactiondiarylacetylenesreactiondiarylacetylenesdiarylacetylenes presentspresents presents abearinga syntheticsynthetic a bearingbearing synthetic one interestinterest non oneone interest‐‐ functionalized functionalizednon non andand‐‐functionalized functionalized willandwill bewillbe investigatedinvestigated phenylbe investigated phenylphenyl group, inin group, group, more more thethe in more reactionreaction details. details.thethe reactiondetails.reaction FromFromtooktook From tookplace unsymmetricaltookunsymmetrical unsymmetrical place placeefficiently efficientlyefficiently reactiondiarylacetylenesreactiondiarylacetylenesreaction presents presentspresents bearinga synthetic bearing bearing aa syntheticsynthetic one interest one nonone non-functionalized interest ‐‐interestfunctionalizednonfunctionalized and‐functionalized willandand bewillwill investigatedphenyl bebe phenyl investigatedinvestigatedphenyl group, group, ingroup, morethethe in thein reaction morereactionmorethe reactiondetails. reaction details.details. tooktookFrom took took FromplaceFrom placeunsymmetrical place unsymmetrical efficientlyefficientlyunsymmetrical efficiently with diarylacetyleneswithdiarylacetylenes witha variety a variety bearingof substituents bearingof onesubstituents nonone on‐ functionalizednon the ‐‐onfunctionalizedfunctionalized otherthe otheraryl phenyl group,aryl phenyl group, group, except group, the except inreaction thethe the reactioninreaction case thetook ofcase tooktookplace bulky of place efficientlybulky aromatic efficiently aromatic withdiarylacetylenesdiarylacetyleneswithdiarylacetylenes withdiarylacetylenes awitha varietyvariety a avariety variety of bearingofbearing substituents substituents of bearingbearingof substituents onesubstituentsone onenononenon on on‐ ‐nonfunctionalizednon functionalized theonthe ‐‐onfunctionalized functionalized otherthe otherthe other otherarylaryl phenylphenyl aryl group, group,aryl phenylphenyl group, group,group,group, exceptexcept group,group, except the theexcept in in reaction thereactionthe the thein reaction inreaction casethe casethe took took case ofcaseof tooktook place bulky placebulkyof of placebulkyplace efficientlybulkyefficiently aromaticaromatic efficiently efficientlyaromatic aromatic diarylacetyleneswith witha variety a variety ofbearing substituents of substituents substituentsone non on‐functionalized the on otherthethe other aryl phenyl arylgroup, group,group, except theexcept in reaction the inin casethethe took caseof placebulky of bulkyefficiently aromatic aromatic withwithsubstituentssubstituents with asubstituentsasubstituents varietyvariety a variety and ofof substitutionsubstitution and andsubstituents substituentsof substitutionsubstitutionsubstituents at onthetheon at at theorthothe on thethe other ‐otherthe‐ orthoposition.ortho other ‐ ‐arylposition.position.aryl arylgroup,group, group, exceptexcept except inin the thein casecasethe caseofof bulky bulkyof bulky aromaticaromatic aromatic withsubstituentssubstituents withsubstituentswitha variety aa andvarietyvariety of substitutionsubstitutionand substituents of ofsubstitution substituentssubstituents at thetheon at orthoortho thethe onon ortho‐ ‐othertheposition.the ‐otherposition.other aryl arylgroup,aryl group,group, except exceptexcept in the inin casethethe casecaseof bulky ofof bulkybulky aromatic aromaticaromatic substituentssubstituentssubstituents and substitution and substitutionsubstitution at the at ortho thethe ‐orthoposition.‐‐position. substituentssubstituentsSupplementarysubstituentsSupplementary and and Materials:substitution andsubstitution substitutionMaterials: The at at the followingtheThe at ortho ortho thefollowing ‐ortho ‐position.position.are ‐position.available are available online online at www.mdpi.com/2073 at www.mdpi.com/2073‐4344/7/12/365/s1,‐4344/7/12/365/s1, substituentsSupplementarySupplementarysubstituentsSupplementarySupplementary and Materials: Materials:substitutionand Materials: substitutionMaterials: TheThe at Thefollowing thefollowingThe at orthofollowing thefollowing ortho‐ areposition.are ‐availableposition.are availableare available available onlineonline online online atat www.mdpi.com/2073 www.mdpi.com/2073at at www.mdpi.com/2073 www.mdpi.com/2073‐4344/7/12/365/s1,‐4344/7/12/365/s1,‐4344/7/12/365/s1,‐4344/7/12/365/s1, Supplementary(1) GeneralSupplementary information, Materials: Materials: (2) AlkyneThe followingThe syntheses, followingfollowing are (3) available 2,3are‐ diarylbutadieneavailable online online at syntheses.www.mdpi.com/2073 at www.mdpi.com/2073 ‐4344/7/12/365/s1,‐‐4344/7/12/365/s1, SupplementarySupplementary(1) GeneralSupplementary(1)(1) GeneralGeneral information, Materials: Materials: information,information, Materials: (2) AlkyneTheThe (2)(2) following TheAlkynefollowingAlkyne syntheses, following syntheses,syntheses, areare (3) available2,3availableare (3)‐(3) diarylbutadieneavailable 2,32,3 ‐ ‐diarylbutadieneonlinediarylbutadieneonline online atat syntheses. www.mdpi.com/2073www.mdpi.com/2073 at syntheses.syntheses.www.mdpi.com/2073 ‐‐4344/7/12/365/s1,4344/7/12/365/s1,‐4344/7/12/365/s1, Supplementary(1)(1) GeneralSupplementary(1)Supplementary(1) General General information,information, information, Materials:information, Materials:Materials: (2)(2) AlkyneThe (2) (2) Alkyne AlkyneThefollowingThe syntheses,syntheses, followingfollowing syntheses, syntheses, are (3)(3) 2,3 2,3availableare are(3) (3)‐‐diarylbutadiene 2,3 available2,3available‐‐diarylbutadiene diarylbutadieneonline onlineonline at syntheses.syntheses. www.mdpi.com/2073 atat syntheses. syntheses. www.mdpi.com/2073www.mdpi.com/2073 ‐4344/7/12/365/s1,‐‐4344/7/12/365/s1,4344/7/12/365/s1, (1) General(1) General information, information, (2) Alkyne (2) Alkyne syntheses, syntheses, (3) 2,3 (3)‐diarylbutadiene 2,3‐diarylbutadiene syntheses. syntheses. (1)(1)Author General General(1)Author GeneralContributions: information, information, Contributions: information, (2) (2)C.B. Alkyne Alkyne (2)and C.B. Alkyne C.F. syntheses, syntheses,and conceived C.F.syntheses, conceived(3) (3) 2,3 2,3and (3)‐‐diarylbutadienediarylbutadiene 2,3designed and‐diarylbutadiene designed the experimentssyntheses. syntheses. the syntheses.experiments and wrote and wrotethe paper; the paper; M.K.A. M.K.A. (1)AuthorAuthor General(1)AuthorAuthor Contributions:General Contributions: information, Contributions: Contributions: information, C.B. (2)C.B. Alkyne andC.B. (2)and C.B. Alkyne C.F. andC.F. syntheses,and conceived C.F.conceived syntheses,C.F. conceived conceived (3) and2,3 and (3)‐diarylbutadiene designed and2,3designed and‐diarylbutadiene designed designed the the experiments experiments thesyntheses. the experiments syntheses.experiments and and wrote andwrote and wrote the wrotethe paper; paper;the the paper; paper;M.K.A. M.K.A. M.K.A. M.K.A. AuthorperformedAuthor Contributions: the Contributions: experimental C.B. and C.B.work C.F. and and conceived C.F. analyzed conceivedconceived andthe analytical designed and designed data.the experiments Z.K.thethe experiments experimentssupervised and wrotethe and work wrote the at paper; thethe Universitépaper; M.K.A. M.K.A. AuthorAuthorperformedAuthorperformedperformed Contributions:Contributions: the Contributions: experimental thethe experimentalexperimental C.B.C.B. andC.B.workand C.F. C.F.and andworkwork conceivedconceivedC.F. analyzed andand conceived analyzedanalyzed andtheand analytical designed designed and thethe analyticaldesignedanalytical data. thethe experiments experiments Z.K. data.thedata. experimentssupervised Z.K.Z.K. supervised supervised andand the wrotewroteand work wrote the the thethe atwork work paper;paper; thethe at Universitéatpaper; theM.K.A.theM.K.A. UniversitéUniversité M.K.A. AuthorperformedAuthorperformedAuthorperformed Contributions: thethe Contributions:Contributions: experimentalexperimental thethe experimentalexperimental C.B. work andC.B.C.B. C.F. work andworkandand conceived C.F.analyzed analyzedC.F. andand conceived analyzedconceivedanalyzed thetheand analyticalanalytical thedesigned theandand analyticalanalytical designeddesigned data. the data.experimentsZ.K. data. thethe supervisedexperimentssupervised Z.K.experimentsZ.K. supervised supervised and thethe wrote andand work the the wrotewrote the work workatat paper;the the thethe at atUniversité paper; thepaper;the M.K.A. UniversitéUniversité M.K.A.M.K.A. performedFrèresperformedFrères Mentouri the Mentouri experimental the Constantine experimental Constantine work (Algeria). workand (Algeria). analyzed and analyzed the analytical the analytical data. data.Z.K. supervised Z.K. supervised the work the workat the at Université the Université FrèresperformedperformedFrèresFrèresperformed MentouriFrères Mentouri the Mentourithe Mentouri experimental experimental Constantinethe Constantine experimental Constantine Constantine work (Algeria).work (Algeria). work(Algeria).and and (Algeria). analyzed analyzed and analyzed the the analytical analytical the analytical data. data. Z.K.data. Z.K. supervised Z.K.supervised supervised the the work work the workat at the the at Université Université the Université performedFrèresperformedFrères Mentouri the Mentouri experimental the Constantine experimental Constantine work (Algeria). work and (Algeria).(Algeria). analyzed and analyzed the analytical the analytical data. data.Z.K. supervisedZ.K. supervised the work the work at the at Université the Université FrèresFrèresFrères Mentouri Mentouri Mentouri Constantine Constantine Constantine (Algeria). (Algeria). (Algeria). FrèresFrèresConflictsFrèresFrères Mentouri ConflictsConflictsMentouri of Mentouri Mentouri Interest:Interest: Constantine ofofConstantine Interest:Interest: Constantine Constantine The authors TheThe(Algeria). (Algeria). authorsauthors (Algeria). (Algeria). declare declaredeclare no conflictconflict nono conflictconflict of interest.interest. ofof interest.interest. ConflictsConflictsConflicts of Interest:Interest: of of Interest: Interest: The authorsauthors The The authors authors declare declare declare no conflictconflict no no conflict conflict of interest.interest. of of interest. interest. ConflictsConflicts of Interest: of Interest: The authors The authors declare declare no conflict no conflict of interest. of interest. ConflictsConflicts Conflicts of of Interest: Interest: of Interest: The The authors authorsThe authors declare declare declare no no conflict conflict no conflict of of interest. interest. of interest. Conflicts Conflicts of Interest: of Interest: The authors The authors declare declare no conflict no conflict of interest. of interest.

Catalysts 2017, 7, 365 7 of 9 a variety of substituents on the other aryl group, except in the case of bulky aromatic substituents and substitution at the ortho-position.

Supplementary Materials: The following are available online at www.mdpi.com/2073-4344/7/12/365/s1, (1) General information, (2) Alkyne syntheses, (3) 2,3-diarylbutadiene syntheses. Author Contributions: C.B. and C.F. conceived and designed the experiments and wrote the paper; M.K.A. performed the experimental work and analyzed the analytical data. Z.K. supervised the work at the Université Frères Mentouri Constantine (Algeria). Conflicts of Interest: The authors declare no conflict of interest.

References and Notes

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