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Baran Group Meeting Samer Gnaim Sulfur Ylide 08/01/20 Previous Baran Lab Group Meeting Topics Centered on Sulfur: Sulfur Containing Natural Products (Knouse, 2019) Sulfur in Organic Synthesis (Yan, 2016) Me Me Ylide Stability S First reported First use of ylide Sommelet-Hauser First use of sufonium ylide by Michaelis by Luscher rearrangement ylide by Johnson R Me

1919 1930 1953 1962 S S S S Me Me Ph Ph Ph Ph Ph Ph 1894 1922 1938 1958 Generated o o o o 5 min (20 C)2.5 min (25 C) 30min(-15 C) First charactized ylide, First reported sulfur Witing reaction Corey used the at -70 C isolated by Staudinger ylide by Ingold sulfonium/sulfoxonium methlide Isolabile Ylides Introduction Me Me Me Me S S Me Me Me Me Definition: Sulfur ylides are zwitterionic compounds defined by a and a S S neighboring positively charged sulfur .It also called -sulfuranes. O O R R PhO2S SO2Ph R R Me OEt S R S R b.p. 135oC/0.8mm b.p. 40oC/0.003mm m.p.134oC m.p. 214oC R R Note: Generally, the order of ylide stability has been shown to be S>P >N. Main use: Ylides have long been used as one-carbon synthons in a number of classical transformations, most notably for the synthesis of small rings such as , Formation by Deprotonation of Preformed Salt and cyclopropanes through ylide addition to electron-poor -systems. H R The popularity of the method is illustrated by the very large number of citations of Corey's path A S BH work (~2000). R

H R H R - B Types of Sulfur Ylides: B path B S S R R H H R R R O O O R R R S R S R S R path C S R R S R R S BH O H R R R R R R R Group Meeting includes: Sulfonium Sulfoxonium Thiocarbonyl Sulfinyl Sulfonyl Group Meeting does not includes: - Introduction of classes of sulfur ylides - Johson-Corey-Chaekovsky reaction - Preparation and synthesis of sulfur ylides. - Metal Complexes of Sulfur Ylides. - Reaction of sulfur ylides R N S R S S R Books and reviews: Russ. Chem. Rev., 2001, 70, 655 O R R Chem. Soc. Rev., 2017, 46, 4135 Eur. J. Org. Chem. 2013, 5005 Iminosulfuranes Thiopyranoxide Thiopyran Acc. Chem. Res. 2004, 37, 611-620 Top Curr Chem, 2018,15, 376

Science of Synthesis, 2004, 27, 21 Chem. Rev. 2019, 119, 8701 Baran Group Meeting Samer Gnaim Sulfur Ylide Chemistry 08/01/20 Thiocarbonyl Ylides extrusion

The Forms of Methylenesulfonium Methylide N N R3 R1 R3 R1 or chloforom CN H H H H R R 4 S 2 reflux R4 S R2 S CN S H S H S H S H Starting material can be prepared by chlorination of azines followed by H H H H H H H H H2N NH2 cyclization with hydrogen sulfide or by the cyclization of azines with hydrogen sulfide followed by dehydrogenation using diethyl azodicarboxylate. O The electronic structure of thiocarbonyl ylides has been extensively studied and the In an analogous manner, the extrusion of carbon dioxide from O proportions of the five possible resonance forms of the parent ylide have been calculated 1,3-oxathiolan-5-ones is also known. R R using natural resonance theory. J. Org. Chem. 1997, 62, 1766 R S R J. Org. Chem., 1966, 31, 3731 J. Org. Chem, 1972, 37, 4045 J. Am. Chem. Soc, 1980, 102, 744 Synthesis of Thiocarbonyl Ylides X- R1 S R Addition of and Carbenoids to Thiocarbonyl R1 S X R R1 S R Base Ts S R2 R S R R R2 R Ts Ts 2 Cu(acac)2 cat. Ts The range of substrates prepared using this method is limited to R or R being a S 1 2 N2 benzene, reflux S nitrogen based functional group, presumably to facilitate alkylation of the thiocarbonyl S 99% S compound. Also R1 and R2 must not possess alpha-hydrogens. The generation of carbenes by transition-metal-catalyzed decomposition of For example compounds is frequently more efficient than their photolysis and thermolysis reactions R and allows the to be generated under milder and safer conditions. R2 O 2 S Rh and Cu and the most used metal complex for the generation of the ylide. 1. S The first step is forming thioimidate Br Cl O intermediate, followed by cyclization. J. Am. Chem. Soc, 1990, 112, 2003 R1 NH2 N 2. Et N (2 eq.) R1 3 H O O 1,3-Elimination Reaction Me H2N NH2 Me IPh DCM, r.t., 24h S Me Me NH2 Thermal Decompositions S 50% O O H2N R TMSO- 100 oC Note: When the thiocarbonyl compound bears no such alpha-heteroatoms, a transition- CH2 metal catalyst is required for the reaction to occur. TMS S TMS HMPA R S TMS R S J. Am. Chem. Soc. 1985, 107, 7178 O - (TMS)2O R= aryl, alkyl R R Cl Cl Halosilanes CHCl , aq. NaOH Br Cl 3 or by using: R S R S Cl Cl 100 oC, HMPA HgPh R S CH Seyferth reagent R S TMS 2 R= aryl or withdrawing groups -TMSCl R= H, aryl, akyl One of the principle restrictions of this method is the need for non-enolizable substrates, 1,3-Elimination reactions are useful method for the generation of relatively unsubstituted as the generation of the carbene is performed under quite basic conditions. thiocarbonyl ylides from simple starting materials, and are commonly employed for the J. Org. Chem. 1972, 37, 1537 Pol. J. Chem. 1996, 70, 1093 synthesis of thiocarbonyl ylide analogues such as oxonium and azomethine ylides Baran Group Meeting Samer Gnaim Sulfur Ylide Chemistry 08/01/20

Reactions of Thiocarbonyl Ylides from Nitrogen Extrusion The chemistry of thiocarbonyl ylides is very dependent on their structure. The most MeO2C CO2Me common applications of thiocarbonyl ylides are in the synthesis of thiiranes and in 1,3- N N DMAD dipolar cycloaddition reactions. t tBu Bu Me-cyclohexane, 40 oC t S tBu Bu 1,3-Dipolar Cycloaddition - Synthesis of sulfur containing heterocycle 67% S J. Org. Chem. 1972, 37, 4045 R 2 MeOOC R2 1,3-Electrocyclization Reactions S yields: O MeOOC COOMe N N tBu tBu MeOOC S O 23% - 78% Me-cyclohexane N t o R1 R1 = SR, SAr, NR2, Ar, CN. NH tBu S Bu 80 C, 5h S H R R2 = Ar, CO2R. 1 trans cis J. Org. Chem. 1977, 42, 1633 N N t t Note: Thiocarbonyl ylides generated from reaction between thiocarbonyl compound and Me-cyclohexane Bu Bu a carbene cannot be used in such reactions. t t o Bu S Bu 80 C, 5h S cis trans Intramolecular Cycloaddition O Note: According to the Woodward–Hoffman rules for conservation of orbital symmetry, Me this cyclization occurs in a conrotary fashion Tetrahedron Lett., 1970, 37, 4689 Br N 1. xylene, rt, 12h S Alkene Formation from Thiocarbonyl Compounds N S 2. Et N, reflux, 1.5h CO Me Ph CO Me Cl O 3 H S N2 Ph 2 2 H 81% Rh (OAc) cat. 2 4 CO Me o Ph 2 Ph Ph MeO2C CO2Me toluene, 50 C, 5h S Ph CO2Me Tetrahedron Lett. 1992, 33, 5877 53%, 3:1 from 1,3-Elimination Reactions Not all thiiranes are stable and some undergo spontaneous extrusion of sulfur to give the corresponding alkenes. For those that are stable, the alkene can be generated by the O addition of a . This type of extrusion reaction represents a convenient method o PhCHO for the preparation of sterically hindered alkenes. TMS S Cl 110 C, DMF CH2 Ph S S 91%, CO Et N2 2 S Rh (OAc) cat. Note: The cycloaddition reactions of thiocarbonyl ylides and cyclic symmetrical dipolaro- O 2 4 MeO2C CO2Me o O CO2Et philes tend to be highly diastereoselective Tetrahedron Lett., 1985, 26, 3011 toluene, 50 C, 5 min OBn OBn Me S Me CO2Me Synthesis, 1987, 1116 Helv. Chim. Acta,1996, 79, 1785 Me Me o 110 C H CO2Me H H H H 1,5-Electrocyclization Reactions Me TMS S TMS DMPU Me R O R1 O 1 R O R4 Me 3 Me LiClO4, THF Me Me OMe S R3 4 steps R2 S R4 R2 H O t H O Stabilized thiocarbonyl ylide (R1 = Bu, Ph) preferentially undergoes 1,5-electrocyclization, Hippolachnin H whilst (R1 = OEt) favors 1,3-electrocyclization and (R1 = NMePh) gives both possible J. Am. Chem. Soc., 2017, 139, 11706 electrocyclization products Me Me Helv. Chim. Acta, 1998, 81, 285 Baran Group Meeting Samer Gnaim Sulfur Ylide Chemistry 08/01/20

O O O Direct Generation of Sulfoxonium Ylides from Sulfoxides Me Me R1 IPh CS2 Me S-attack O Me S C S Me S S R Cu(acac)2 Me 85% R1 O O O S R O Tetrahedron Lett, 1987, 28, 4449 R2C S R 1,5-Electrocyclization with thioketene R1 R1 O N O R tBu 2 tBu O-attack S Rh2(OAc)4 cat. S R R C S R R 1 1 R R C S MeO C CO Me o 1 1 t 2 2 toluene, 50 C, 5h t Bu Bu CO2Me Aryl and dihalocarbenes generally lead to deoxygenation of the sulfoxide giving the MeO2C corresponding sulfide and carbonyl. Acylcarbenes, which are readily prepared by photol- ysis, thermolysis, or transition-metal-catalyzed decomposition of the corresponding diazo MeO O tBu cyclization compounds, show a strong preference for reaction at the sulfur atom of sulfoxides to give the corresponding sulfoxonium ylides t Tetrahedron Lett,.1989, 30, 1249 MeO C S Bu 2 HgBr Br Synthesis of Sulfoxonium Ylides Br O Ph Seyferth reagent compounds can be The chemistry suldoxonium ylides is dominated by their ability to react firstly as NH Br O S S Br used to generate sulfoxonium ylides nucleophiles and secondly as electrophiles. Sulfoxonium ylides are quite stable Ph Ph benzene, reflux, 2h Ph bearing two halogens from the species and can be stored for months under nitrogen at 0 oC. Br corresponding sulfoximides. The reaction of sulfoxonium ylides with electrophiles often creates R2N O Direct Sulfoxonium Ylide formation - Vaitla - 2017 new stereogenic centers. For this reason, aminosulfoxonium ylides, S Me CH2 O which are chiral, have been prepared in optically active form for application PhI(OAc)2 in asymmetric synthesis. S O O O O R1 R1 2% Rh2(OAc)4 O R1,R = MgO, DMSO R R R R R O O aryl, alkyl R R O O S - O Base O O R X R MW, 5 min I X S R Ph R1 R1 R S R S S R R O R R CH2 R R -HX Org. Lett. 2017, 19, 6688 Reactions of Sulfoxonium Ylides S O NPh O NPh O N O Johnson-Corey-Chaykovsky R R R R O S S S S R R PhHN R Ph R N R O R R R R NR1 Chem. Soc. Rev., 2017, 46, 4135 Me R1N O B- R R S S NPh S N Me Me R R Acc. Chem. Res. 2004, 37, 611-620 PhN C NPh X- R S R R Cl N Cl O O Science of Synthesis, 2004, 27, 21 Other electrophiles that can used to form stabilized sulfoxonium ylides: R1 R halo-cyanogen, beta-halo-michael acceptors, electron-deficient alkyne, isocyanates R J. Org. Chem. 2017, 82, 8220 R1 Baran Group Meeting Samer Gnaim Sulfur Ylide Chemistry 08/01/20

Hopmann R1 Ring Expansion of Epoxides and Aziridines 2.5 mol% [Ir(COD)Cl]2 R N Me Me O O H N N "5 mol% 1,10-phenanthroline N O R O Me 2 X S S R o X O Me CH O S R 5 mol% NAOTf, DCE, 80 C 2 N Me CH2 N R Me X 1 X O 94% R= PhSO Ph Ph Ph 2 Ph R= aryl, alkyl X= N, CH 72% R 2.5 mol% [Ir(COD)Cl]2 J. Org. Chem., 1983, 48, 5133 R =H, Me 1 DCE, 80 oC HN N Insertion Reactions into X–H Bonds or fused ring system R X 1 Baldwin - 1993 J. Org. Chem., 2016, 81, 4158 X O O O When 1,10-phenanthroline and NaOTf were added as ligand and additive, Me 5 mol% Rh2(TFA)4 S Baldwin (Rh): 2 examples respectively, the key iridium carbenoid preferred to react with the pyridine lone pair. Me DCE, reflux R R Mangion (Ir): 5 examples Hopmann’s Indole Synthesis NHBoc or 1 mol% [Ir(COD)Cl]2 NBoc n 2 mol% [Ir(COD)Cl]2 DCM, rt O O H N n= 0-2 n= 0-2 Me 2 10 mol% p-TSA Ar S R N J. Chem. Soc. Chem. Commun., 1993, 18, 1434 Ar Me 1 toluene, 140 oC, uW H The efciency of these reactions drew interest to the extent that Merck began their own 1 eq. 2 eq. research programme, and in 2009 Mangion and co-workers published a more general A cascade of carbenoid formation and N–H insertion followed by via methodology, based on Baldwin and co-workers’ original conditions. N acid-catalysed formation, substitution and aromatisation was Merck - 2009 active, explaining why the aniline involved in the N–H insertion step Ar was not incorporated into the fnal product. O +NH Ph O Angew. Chem. Int. Ed., 2017, 56, 4277 2 R= aryl, alkyl OMe 1 mol% [Ir(COD)Cl]2 C–H insertion reactions OMe X= N, O, S S 2 eq. R-XH, DCM, rt H O Me XR O O 2 mol% [Ir(COD)Cl]2 R Me Me N 2 Org Lett, 2009, 16, 3566 S R R Ar Me 1 2 10 mol% p-TSA When Rh (TFA) was used as the catalyst for the reaction with aniline, only 22% of the Me o 2 4 toluene, 140 C, uW Ar N Me desired product was obtained. As a rationale for this observation the authors proposed that the DMSO released after formation of the metal-carbenoid poisoned the catalyst R1 By combining enamines with sulfoxonium ylides, it Further studies proved that Au and Pt salts were also competent catalysts for these O was possible, through the action of an iridium catalyst, transformations. NH to aford the products of C–H insertion, which in the O NCbz Me presence of an acid additive readily cyclised to form O O O NCbz N highly substituted pyrroles t-BuOK, S(O)Me3I Me N S F R Me DMSO N 1 Angew. Chem. Int. Ed., 2017, 56, 4277 NBocH Me 71% H + NHBoc O O NH2 C–H Functionalization NCbz O Li and co-workers Mechanism N OH 1 mol% [Ir(COD)Cl] O O R2 6 mol% [RhCp*(MeCN)3](SbF6)2 N H N 2 Me o S NBocH 87% toluene, 80 C 10 mol% Zn(OAc)2 N O Me R1 - R1 o O3SO O DCE, 80 C, 16h R R 3 Org. Lett. 2011, 13, 20, 5480–5483 3 Org. Lett. 2017, 19, 4307 R2 Baran Group Meeting Samer Gnaim Sulfur Ylide Chemistry 08/01/20 Me Li and Alissa Synthesis of Sulfonium Ylides DG DG NOMe Deprotonation of Sulfonium Salts O O H Me Conditions R S R R R Me O R Base R O Ph S R S R X- R R Li: Selected examples Aissa: 90% -HX

6 mol% [RhCp*(MeCN)3](SbF6)2 N N Substitution of Groups on Sulfonium Salts 60 mol% Zn(OAc)2,2 eq. PivOH N DCE, 80 oC, 16h N R R i-Pr R Y R R Aissa: S - R R 2 mol% [Cp*RhCl]2 Ph X S R S R O R X- 10 mol% AgSbF ,1 eq. NaOAc O -Y R -HX R 6 Aissa: 96% Aissa: 77% HFIP, 60 oC, 17 - 48h Y= OR, NR2, Ph Li: 96% Li: 90% Org. Lett,. 2017, 19,, 5256 Angew. Chem. Int. Ed., 2017, 56,13117 O Reaction with Aromatic Compounds O O N O O S Ac2O, reflux S O N O Me NO R R R R Cl O 2 S NO NO R R DCM, -78 oC S 2 S 2 R R Me CH2 Me

DMSO, 45 oC 15 : 1 other regeant: trifluoroacetic anhydride, dicyclohexylcarbodiimide, phosphorus pentoxide/Et3N 33% Me Nucleophilic Attack on Vinyl Sulfonium Salts Methylation is directed to the ortho position in preference to the para-, and with meta- substituted nitrobenzenes the methylation proceeds primarily at the more hindered ortho position. J. Org. Chem., 1966, 31, 243 R R Nuc- R R S S Bio-organic Application of Sulfoxonium Ylides R R Nu

O O O O CO Et + 2 Me H Me HS R EtO2C CO2Et o Me S Tag S Enzyme S DCM, -20 C R Tag P1 Me P1 Me BF4- S CO Et R Me 2 R

Reaction of Sulfides with Carbenes

R R R S R O R R S R S R Tag P1 Enzyme Like certain thiocarbonyl compounds and sulfoxides, a variety of sulfides can trap carbenes to give sulfonium ylides. Diazo compounds are the most commonly employed ACS Chem. Biol. 2020, 15, 718 carbene precursors. Baran Group Meeting Samer Gnaim Sulfur Ylide Chemistry 08/01/20

Maulide - 2010 Formal (4+1) Cycloaddition O O Holy - 1976 Et2O, DCM or toluene R O R2 (RfO) SPh 2 Me R 2 2 R1 NO2 - NaH, CuI 1 rt, 2h 57-99% Ph I O N O S S R:Me: 64% Ph Ph R Me Me DMF Ph Maulide and co-workers employed Martin’s sulfurane for direct ylide transfer to , R H: 71% diketones, and keto esters in very good yields and under mild conditions. J Org Chem., 1976, 41, 4033 Angew. Chem. Int. Ed., 2010, 49, 8979 (4 + 1)-Cycloaddition/Rearrangement of Nitrostyrenes Reactions of Sulfonium Ylides Xiao - 2008 Mechanism 10% cat. O of Alkenes O Me S NO2 10% DMAP Ar S HN O O Trost - 1966 R Me N NH2 1 CHCl3, rt R Ar Cl H PhOC 2 R1 cat O Me R2 CuSO S 4 COPh COPh This transformation affords a range of oxazolidinones in moderate to good yields with Ph Me 5% good to excellent diastereoselectivities. PhOC J. Am. Chem. Soc,. 2008, 130, 6946 The expected cyclopropane was only isolated in trace quantities, instead, cyclopropane Bolm - 2012 tri-mer side product was the major product J. Am. Chem. Soc.1966, 88, 1587 O Ph-OMe Cohen and Julia MeO-Ph 10% Cu(OTf)2 O NH O Me Ph 44% Cu(acac)2 N 11% tol-BINAP O or Cohen: 35% S N N S Ph Me o Julia: 86% t Cl 1 eq. Na2CO3, THF, -20 C H2C Ph 15% Cu(pentacac)2 Bu tBu Ph O Ph-OMe It was not until 1999 that the frst enantioselective process was developed by Müller and co-workers. By using either a Cu(I) or Rh(II) chiral catalyst could be used to generate Cu -HCl N -SMe cyclopropanes in moderate e.e%. N 2 J. Am. Chem. Soc., 1974, 96, 5627 tBu Gu - 2016 J. Am. Chem. Soc., 2012, 134, 6924 Xiao - 2014 Ph 5% (TPP)FeCl 44 examples Mechanism F3C S CsF, DMA, rt Ph Ar CF3 67-94% Ar Br 5% Pd2(dba)3CHCl3 -OTf >d.r. 98:2 O O Me Br O 11% L* S Org. Lett,. 2016, 18, 2471 o N O EtO Me CHCl3, -40 C N OEt Cyclopropanation of Allenamides Ts Ts benzoxazinanone Maulide - 2014 81%, 92% ee NC CO Me NC CO2Me 2 Ph 5% [PPh3AuCl] Ph Nat. Commun., 2014, 5, 5500 5% AgOTs - In 2016, the same reaction was revisited in the context of Fe-. S C N N Ph Ph Ts DCM,rt Ts - Thereafter, the same group explored the ability of copper-allenylidene intermediates to 88% act as reactive 1,4-dipoles. The reaction works with ketones, esters, nitriles and halogens - In 2019 the groups of Gouverneur and Shibata showed that this could be extended to CF3-substituted benzoxazinanones. J. Am. Chem. Soc,. 2016, 138, 8360 Chem. Eur. J., 2014, 20,10636 Angew. Chem., Int. Ed,. 2016, 55, 2840 Baran Group Meeting Samer Gnaim Sulfur Ylide Chemistry 08/01/20

Xiao - 2017 Maulide R O O 5% [(PPh3)AuCl] O Br O Me O 5% AgSbF R= works with aryl and alkyl 10% cat, CsF via R X 6 S n O X DCM, rt X=O or NR OTBS R1 Me toluene, -20oC S O R Ph Ph n R 1 O 2 Angew. Chem., Int. Ed., 2012, 49, 8979 Mechanism - Supported by DFT Eur. J. Org. Chem,. 2017, 2017, 233 R R O O R O Formal (3 + 1) Cycloaddition Ph O S O Doyle - 2017 3,3 O -SPh2 O O O OTIPS Mechanism TIPSO COOMe O Me Me COOMe 2.5% Cu(OTf) PhMe Au Au 2 Au S SPh Ph Me 6% L, DCM, rt N2 Me O In the same study, Maulide and co-workers investigated the behaviour of doubly 85%, 96% ee Ph stabilised ylides in an intermolecular context, analogous to the Skrydstrup procedure. Angew. Chem., Int. Ed., 2017, 56, 7479 While such reactions resulted in the efcient formation of 2,3,4-trisubstituted furans, higher temperatures were required on account of the lower reactivity of the starting materials Formal (3+2) cycloaddition - Furan synthesis Maulide

In 2012, the groups of Skrydstrup and Maulide independently reported synthesis of O O O OMe furans based on a cationic -acidic gold complex promoted a formal (3+2) cycloaddition. 10% Au cat. MeO OMe Ar Toluene, 100oC S Skrydstrup Ph Ph Ar COOMe

O Me O R1 When allyl esters were used as O 5% [(PPh3)Au]NTf2 R1 and R2 O R S stabilising ,the final O 1 R Ph o O R R 2 DCE, 60 C work as aryl and alkyl product of the intermolecular cyclisation 3,3 R 1 can rearrange through a [3,3] sigmatropic O shift, affording dearomatised furanones O O Angew. Chem., Int. Ed., 2012, 51, 4681 bearing a quaternary stereocentre. O

Mechanism 3+3 Annulation Tang - 2012 Me R2 R2 R 2 OAc S O R RS CO2Bn Ph O O 20% DABCO -PhSMe O S C CO Bn Ar X- R K2CO3, acetone, rt R1 R1 R 2 Ar O Me 1 R= Me, Ph Au Au Au via O Ar C

BnO2C SAr Chem. Commun,. 2012, 48, 2900 Baran Group Meeting Samer Gnaim Sulfur Ylide Chemistry 08/01/20

Rearrangement Reactions TMS S CsF, MeCN 2,3-Sigmatropic Rearrangment R S R4 OTf R R R4 R3 R R 2 S S S R3 CsF S 2,3 R1 R1 R1S R4 R R 3 2 R 2 J. Org. Chem. 2017, 82, 4470 Org. Biomol. Chem. 2017, 15, 2716

Rearrangment of Allyl and Propargylsulfdes Modifed Gassman Oxindole Synthesis

CO2Et R3 Ph R2 S C Ph 95% SAr H CO2Et S N R3 CO2Et 2 mol% Rh2(OAc)4 SAr R1 O 0.2% Fe-cat R o or 1 N DCE, 0 C, 10h N N2 DCM, rt 2 CO2Et R2 Me doubly 94% S S Org. Lett., 2011, 13, 1210 procedure. Me Thia-Stevens 1,2-Rearrangement higher When using TBAFe as a catalyst, the reaction was performed chemoselectively in the General Mechanism R R presence of boronates, allyl , secondary anilines, disulfdes and free alcohols. 2 2 S S Nat. Chem. 2017, 9, 970 R3 R1 R3 R1 S S Ring Expansion and Contraction R3 R1 R3 R1 R2 R2 Bz toluene, 90 oC For example DCM, -5 oC S S S Me Me S Bz Me Me Bz O O Bz Chem. Soc., Perkin Trans, 1981, 1, 1953 O O t 65% CO2 Bu 2 mol% Rh2(OAc)4 J. Am. Chem. Soc., 1975, 97, 6878 DCM, reflux N2 In the case of 5 and 6 CO tBu chloramine T o S 2 140 C membered ring, the S S MeOH, 20 oC S 2,3 iminosulfurane ylide is 70% N S NTs isolable, and it is not the J. Org. Chem. 2015, 80, 7581 Ts case with 7 membered rings Stevens vs Sommelet-Hauser R SPh thia-Sommelet-Hauser Rearrangement H CO Et R 2 2.5 mol% hemin RO C CO2Et 2 Ph N solvent PhS SPh SPh 2 1 0.5 mol% Rh2(TFA)4 RO2C S EWG RO2C EWG toluene, 1 min SPh EWG THF, 80 oC, R= Me: 1= 71% N2 R o CO Et H2O, 40 C, R= NO2:2= 94% 2 The frst rhodium-catalysed thia-Sommelet–Hauser reaction between diazo(aryl)acetates Me 2 and arylsulfdes was reported by Wang’s group in 2008. Chem. Commun. 2017, 53, 6219