Recent Progress in the Cross-Coupling Reaction Using Triorgano- Silyl-Type Reagents
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SYNLETT0936-52141437-2096 © Georg Thieme Verlag Stuttgart · New York 2017, 28, 1873–1884 account 1873 en Syn lett T. Komiyama et al. Account Recent Progress in the Cross-Coupling Reaction Using Triorgano- silyl-Type Reagents Takeshi Komiyamaa Yasunori Minami*b Tamejiro Hiyama*b 0000-0034-7491-161 a Department of Applied Chemistry, Chuo University, Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan [email protected] b Research and Development Initiative, Chuo University, Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan [email protected] Received: 25.02.2017 ployed. To assist the silicon–activator interaction, one to Accepted after revision: 27.03.2017 three electronegative heteroatoms such as a halogen or ox- Published online: 04.05.2017 DOI: 10.1055/s-0036-1589008; Art ID: st-2017-a0142-a ygen are often introduced at the silicon center, mainly for the sake of easy formation of the pentacoordinate silicate Abstract The silicon-based cross-coupling reaction has attracted species responsible for transmetalation to a transition-met- much attention over recent decades because there are many advantag- al catalyst. As a result, these silicon reagents become reac- es in using organosilicon compounds. However, the use of reagents with a triorganosilyl group as a key function remains to be established. tive enough to accomplish the cross-coupling, but mean- This account summarizes our recent progress in cross-coupling chemis- while they become air- and moisture-sensitive. Therefore, try with such silyl reagents. careful attention is required in the preparation and han- 1 Introduction dling of the halo- and oxysilanes. 2 Preparation of HOMSi Reagents from Aryl Bromides and Disilanes 3 HOMSi Reagents from Heteroaromatics and Hydrosilanes In contrast, tetraorganosilanes are characterized by 4 Cross-Coupling Polymerization with HOMSi Reagents their robustness and low toxicity. Accordingly, in terms of 5 Cross-Coupling with Aryl(triethyl)silanes stability and ease of handling, they are favorable. However, 6 Amination of Aryl Halides with N-TMS-Amines such reagents generally do not show enough reactivity for 7 Conclusion and Perspective the cross-coupling due possibly to inferior silicate forma- Key words cross-coupling, silylation, amination, organosilicon reagents, tion. In order to find cross-coupling-active alkenyl(triorga- copper, nickel, palladium no)silanes and appropriate activators, many chemists have made efforts to find a solution. Some triorganosilyl-type re- agents are summarized in Figure 1. Hatanaka and Hiyama 1 Introduction first discovered that structurally simple vinyl(trimeth- yl)silanes coupled with aryl iodides upon activation by The cross-coupling reaction has been developed as a tris(dimethylamino)sulfonium difluorotrimethylsilicate common tool to form carbon–carbon and carbon–heteroat- (TASF).3 More than a decade later, Denmark disclosed that om bonds in π-conjugate systems and allows the construc- 1-alkenyl-1-methyl-silacyclobutanes underwent cross-cou- tion of a wide variety of frameworks of potent pharmaceu- pling in the presence of tetrabutylammonium fluoride ticals, agrochemicals, and electronic materials.1 To achieve (TBAF)4 and observed a ring-opening reaction of the four- the bond formation, the use of nucleophilic organometallic membered silacycle by water in TBAF to produce a silanol. reagents such as lithium, magnesium, zinc, aluminum, tin, They considered that this silanol2c was the true active spe- boron, silicon, zirconium, indium and others is essential. cies.4b Similarly, 2-pyridyl,5 2-thienyl,6 benzyl,7 phenyl,8,9 Among them, silicon is attractive as it is an earth-abundant 3,5-bis(trifluoromethyl)phenyl,10 allyl,11 and pentafluoro- element and organosilicon reagents are superior in terms of phenyl12 groups are shown to act as a leaving group to gen- stability, solubility, ease of handling, and accessibility. Now- erate cross-coupling-active fluorosilanes and/or silanols in adays, many types of organosilicon reagents are available situ. A substituent-induced intramolecular activation strat- for alkenylation, arylation, alkynylation, and alkylation of egy is also effective for the coupling. Shindo found that a organic halides.2 For successful reactions, a nucleophilic ac- carboxyl group β-cis to the silicon in alkenyl(trimethyl)sila- tivator such as a fluoride or hydroxide ion is generally em- nes promoted the cross-coupling through intramolecular © Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, 1873–1884 1874 Syn lett T. Komiyama et al. Account 13 activation with Cs2CO3. Nakao and Hiyama invented tuted by a heteroaryl, or 3,5-bistrifluoromethylphenyl alkenyl[2-(HydrOxyMethyl)phenyl]dimethylSilanes (alke- group were suggested by Murata,21 Gevorgyan,22 and Murai nyl-HOMSi), which underwent the cross-coupling reaction and Takai.23 14 even in the presence of K2CO3. As described above, organo-HOMSis are examples of Cross-coupling-active aryl(triorgano)silanes were also cutting-edge reagents for silicon-based cross-couplings disclosed as in the case with the alkenyl silanes. Such active (Scheme 1). This type of cross-coupling reagent is applica- arylsilanes are summarized in Figure 2. Arylsilanes bearing ble not only to alkenylation and arylation, but also to al- allyl,15,16 2-(hydroxymethyl)phenyl,14 or (2-hydroxyprop-2- kylation.14g The organo-HOMSi reagents are stable but be- yl)cyclohexyl17 groups can be used to connect a wide range come highly reactive to effect the cross-coupling upon acti- of aryl groups to various aryl halides. Simple 2-pyridyl-18 vation by a weak base such as potassium carbonate.14 and 2-benzofuryltrimethylsilanes19 were employed for Moreover, the silicon residue, cyclic silyl ether 1, is recover- cross-coupling with aryl iodides in the presence of not only able and recyclable to any organo-HOMSi reagents by treat- a palladium catalyst, but also a stoichiometric transition- ment with an organolithium or organomagnesium reagent. metal mediator. A tert-butyldimethylsilyl group was used in Protection of the proximal hydroxy group makes the the cross-coupling only in the case of using 8-hydroxy-1- HOMSi totally cross-coupling inactive.14e,f Orthogonally re- naphthyl as an electrophile.20 Aryl(triorgano)silanes substi- movable protecting groups such as tetrahydropyranyl (THP), methoxymethyl (MOM), acetyl (Ac), and silyl (SiR3) are applicable. This flexibility permits the construction of a Biographical Sketches Takeshi Komiyama was born metal catalysis. He received a thetic Organic Chemistry, Japan in Saitama in 1991, and is a Poster Award at the 5th CSJ (2016), the Shibuya Ken-ichi Ph.D. student at Chuo University Chemistry Festa (2015), the Ga- Award for Encouragement pre- guided by Professors Tamejiro kuin Kaicho Award from the sented by the Director of Chuo Hiyama and Yasunori Minami. Head of Chuo University Alumni University (2017), and the Pre- His research interest is the ex- Association (2016), the Student sentation Award (Industry Divi- ploitation of novel synthetic Presentation Award at the 71th sion) at the 97th CSJ Annual transformations of organosili- Kanto Branch Symposium orga- Meeting (2017). con compounds by transition- nized by the Association of Syn- Yasunori Minami was born in ing student in 2009, before re- professor. His current research Mie prefecture in 1982. He ceiving his Ph.D. from Osaka interests are synthetic organic spent three months at the Labo- University in 2010 under the su- chemistry using transition-met- ratories of Professor John F. pervision of Professor Nobuaki al catalysts and main group ele- Hartwig (University of Illinois at Kambe. He then joined RDI at ments. Urbana-Champaign) as a visit- Chuo University as an assistant Tamejiro Hiyama was born in he started his research as a Prin- Kyoto University in 2010, he has Osaka in 1946. He was appoint- cipal Investigator at the Sagami been at Chuo University as an ed Associate Professor at Kyoto Chemical Research Center. In RDI Professor. His research University in 1972, completed 1992, he moved to the Research stems from the invention of his Ph.D. under the supervision Laboratory for Resources Utiliza- synthetic methods for the syn- of Professor Hitosi Nozaki at tion, Tokyo Institute of Technol- thesis of biologically active Kyoto University in 1975, and ogy, as a full professor and then agents and liquid crystalline and spent a postdoctoral year at to the Graduate School of Engi- light-emitting materials. Harvard University working with neering, Kyoto University, in Professor Yoshito Kishi. In 1981, 1997. Since retirement from © Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, 1873–1884 1875 Syn lett T. Komiyama et al. Account HO R Me N Si R Ar SiMe SiMe3 (Het)Ar Si 3 R' Si Me2 EWG N Ar' 3 (Het)Ar SiMe2 with TASF with TBAF with TBAF with TBAF with K2CO3 with TBAF and CuI 15a 14a Hatanaka, Hiyama (1988)3 Denmark (1999)4a Itami, Yoshida (2001)5a Nakao, Hiyama (2003) Nakao, Hiyama (2005) Gros (2005)18a F R'' S Me Si O R R Si Si SiMe Me SiMe 3 Me2 2 SiMe R' R' 2 O N N with TBAF with TBAF with CsF with Ag2O with TBAF with TBAF (cat.) and Ag2O Hiyama (2002)6 Trost (2003)7 Hanamoto (2003)8 Itami, Yoshida (2006)16 Murata (2006)21 Whittaker (2008)18b CF3 R' O R'' R R SiMe3 OH R Si O N Me2 HO O SiMe3 Si CF3 R' SiMe (t-Bu) Me2 2 O Si(i-Pr)2 with TBAF with KOSiMe3 and 18C6 with Cs2CO3 10 9 13 Katayama, Ozawa (2003) Anderson (2004) Shindo (2005) with Cs2CO3 with KF and AgNO3 with NaOH Kita (2008)20 Mori (2009)19 Gevorgyan (2010)22 OH F F3C R F F R'' Si R' HO R Me2 R CF3 Si R' Si F Me2 Me2 R' F SiMe (Het)Ar SiMe2 2 with K2CO3 with TBAF with TBAF with Cs CO or K CO with TBAF Nakao, Hiyama (2005)14a Navasero (2006)11 Spring (2010)12 2 3 2 3 Nakao, Hiyama (2011)17 Murai, Takai (2015)23 Figure 1 Cross-coupling-active alkenyl(triorgano)silanes and their acti- Figure 2 Cross-coupling-active aryl(triorgano)silanes and their activa- vators.