Synthesis and Reactions of Bismuthonium Salts and Ylides Bearing an α-Ester Group (original) (raw)

1999, The Journal of Organic Chemistry

Carbon-carbon bond-forming reactions based on ester ylides of the general form R n M)CHCO 2 R′ (M) P, As, Sb, S, Se, Te; n) 2, 3) constitute a research area of considerable significance. 1 This class of ylides shows varied reactivity depending on the nature of a heteroatom involved, but their modes of reaction toward the carbonyl function may be classified into two major categories: Wittig-type olefination and Corey-Chaycovsky-type epoxidation. Recently, we have reported that bismuthonium R-keto ylides Ph 3 BidCHCOR (R) alkyl or aryl), generated in situ from the corresponding onium salts, 2 are moderately stabilized and undergo CC bond-forming reactions with various compounds, which include aldehydes, 3 N-sulfonylaldimines, 4 R-keto esters, 5 o-quinones, 5 acenaphthenequinone, 6 and benzils. 7 However, no information is available for the R-ester-type bismuthonium ylides, R 3 BidCHCO 2 R′, due to the lack of general methodology for the synthesis of bismuthonium salt precursors. 8 As a part of our ongoing study on organobismuth(V) chemistry, we report herein the first synthesis and reactions of bismuthonium salts and ylides bearing an ester group at the R-position. Interestingly, this class of bismuthonium ylides has been found to undergo either Corey-Chaycovsky-type epoxidation or carbon-to-oxygen