Ketones, reaction with sulfur ylids

The generally accepted mechanism for the reaction between sulfur ylids and aldehydes or ketone is which is similar to that of the reaction of sulfur ylids with... 

In the late 1960s, methods were developed for the synthesis of alkylated ketones, esters, and amides via the reaction of trialkyl-boranes with a-diazocarbonyl compounds (50,51), halogen-substituted enolates (52), and sulfur ylids (53) (eqs. [33]-[35]). Only one study has addressed the stereochemical aspects of these reactions in detail. Masamune (54) reported that diazoketones 56 (Ri = CH3, CH2Ph, Ph), upon reaction with tributylborane, afford almost exclusively the ( )-enolate, in qualitative agreement with an earlier report by Pasto (55). It was also found that E) - (Z)-enolate isomerization could be accomplished with a catalytic amount of lithium phenoxide (CgHg, 16 hr, 22°C) (54). 

Just as sulfur ylids react with the carbonyl of an aldehyde or ketone to give an epoxide, tellurium ylids react with imines to give an aziridine. The reaction of an aUyhc tellurium salt, RCH=CHCH2Te Bu2 Br, with lithium hexamethyldisila-zide in HMPA/toluene leads to the tellurium yhd via deprotonation. In the presence of an imine, the ylid add to the imine and subsequent displacement of Bu2Te generates an aziridine with a pendant vinyl group. ... 

Reactions of chiral allylic boranes with carbonyl compounds Reactions of chiral allyl boranes with imines Asymmetric Addition of Carbon Nucleophiles to Ketones Addition of alkyl lithiums to ketones Asymmetric epoxidation with chiral sulfur ylids Asymmetric Nucleophilic Attack by Chiral Alcohols Deracemisation of arylpropionic acids Deracemisation of a-halo acids Asymmetric Conjugate Addition of Nitrogen Nucleophiles An asymmetric synthesis of thienamycin Asymmetric Protonation... 

Trost and co-workers used this type of rearrangement to generate oxaspiropentane derivatives that were converted to cyclo-butane derivatives. In section 8.8.B.ii, oxaspiropentanes such as 61 were prepared by the reaction of ketones and sulfur stabilized cyclopropyl ylids. Treatment of 61 with aqueous tetrafluoroboric acid (HBF4) gave cation 62, which rearranged to 63. Loss of a proton gave the final product, ketone 64. ... 

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