Magnesium carbenoids chiral

As mentioned above, the configuration of the magnesium carbenoid is rather stable at low temperature chiral Grignard reagents having over 90% ee could be generated from optically active 1-chloroalkyl aryl sulfoxides (Scheme 4)20-22... 

In this section, the reactions of gew-dibromocyclopropanes and dibromomethylsilanes with trialkylmagnesate reagents are described. Preparation of a chiral secondary Grignard reagent by alkylation of the chiral magnesium carbenoid species is also discussed. 

Functionalized acyclic magnesium carbenoids can be prepared in THF/N-butyl-pyrrolidinone (NBP) mixtures at low temperatures. Thus, the reaction of the bis-iodomethylcarboxylate 254 with iPrMgCl in THF NBP is complete within 15 min at -78 °C. [133]. The resulting chiral bts-carbenoid 255 is quenched with PhSSPh giving the fois-adduct 256 in 70% yield (Scheme 4.53) [133]. 

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