Peterson alkenation sulfides

Epoxide formation (path c) is an important side reaction which can become the dominant pathway. For example, the addition of sulfur ylides to ketones (equation 2) constitutes a general synthesis of epoxides, while 2-hydroxy sulfides undergo the semipinacol rearrangement under certain conditions (equation 3). Elimination (path d) is observed in some special cases such as 2-hydroxy si lanes (1 X = SiR.i the Peterson alkenation)" and 2-hydroxyphosphonium species (1 X = PRs" " Wittig intermediates). ... 

Synthesis of Vinyl Sulfides. Anion (2) adds to aldehydes, ketones, and enones, in the last-named case in either 1,2- or 1,4-manner depending on the reaction conditions.In the case of 1,2-addition the -hydroxysilane adduct usually cannot be isolated owing to rapid elimination (Peterson alkenation) to vinyl sulfides (eq 5), which can be hydrolyzed to the corresponding aldehydes. The vinyl sulfides are not formed stereoselectively unless there are proximate bulky substituents. Peterson alkenation products have also been observed in the reaction of (2) with amides, ureas, and carbonates. ... 

The anions, generated in situ by desilylation of silylacetylenes, allylsilanes, propargylsilanes, a-silyloxetanones, bis(trimethylsilylmethyl) sulfides, and other silane derivatives,can undergo nucleophilic addition to ketones and aldehydes (eq 11). Al-(C,C-bis(trimethylsilyl)methyl) amido derivatives can add to aldehydes followed by Peterson alkenation to form acyl enamines. Treatment of 2-trimethylsilyl-l,3-dithianes can generate dithianyl anions, which are capable of carbocyclization via direct addition to carbonyl or Michael addition (eq 12). The fluoride-catalyzed Michael additions are more general than Lewis acid-catalyzed reactions and proceed well even for those compounds with enolizable protons and/or severe steric hindrance (eq 13). ... 

An interesting Fe-catalyzed SN2 -like carbene insertion reaction using diazo compounds and allyl sulfides (the Doyle-Kirmse reaction) was reported by Carter and Van Vranken in 2000 [20], Various allyl thioethers were reacted with TMS-diazomethane in the presence of catalytic amounts of Fe(dppe)Cl2 to furnish the desired insertion products with moderate levels of stereocontrol [Equation (7.6), Scheme 7.14]. The products obtained serve as versatile synthons in organic chemistry, e.g. reductive desulfurization furnishes lithiated compounds that can be used in Peterson-type oleftnations to yield alkenes [Equation (7.7), Scheme 7.14] [21]. 

Nucleophilic substitution of a,/3-epoxysilanes followed by the Peterson elimination is valuable for the stereoselective synthesis of alkenes.3 The reactions with lithium phenylsulfide and diphenylphosphide form alkenyl sulfides and alkenylphosphines, respectively, in a stereospecific manner. 7-Metallo-a,/ -epoxysilanes are isomerized to a-siloxyallylmetals by anionic ring opening and subsequent Brook rearrangement (Equation... 

In the original study by Peterson, the alkenation procedure was found to be compatible with sulfur and phosphorus substitution. The alkenation reaction has been tqrplied successfully to a variety of substituted alkenes. Because of the aiuon-stabilizing nature of the thiophenyl, the p-hydroxysiliuie is not isolated and the elimination to the alkene takes place directly to form a 1 1 mixture of ( )- and (Z)-isomers. Ager studied the reaction of the lithio anions of phenyl (trimethylsilyl)methyl sulfides (318) with a variety of carbonyl compounds (equation 72). Yields of this process were good, and addition occurred even with enolizable substrates. This reaction was extended to vinyl sulfones. In contrast to the sulfide case, the substituted sulfone silyl anion behaves as a base, leading to undesired enolization. The best yields were observed for the case where R is a hydrogen or phenyl. 

In 1968, Peterson made the important discovery that the anions resulting from lithiation of [(meth-ylthio)methyl]trimethylsilane and [(trimethylsilyl)methyl]diphenylphosphine sulfide reacted with benzophenone to produce lithiated P-hydroxysilanes, which decompose to give olefins by loss of McgSiOLi. " This olefination reaction resulting in functionally substituted alkenes has been extended to phosphonates and can be considered as an alternative to the Homer-Wadsworth-Emmons reaction. 

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