MIRC reactions with ylides

The formation of the free carbene is also circumvented in certain cyclopropanation reactions involving sulfonium ylides. They readily react with electron-deficient alkenes in a Michael addition/ring-closure sequence (MIRC reaction). This cyclopropane synthesis will be dealt with separately in Section 1.1.3.7. 

The reaction of ylides with alkenes proceeds in two steps according to the MIRC reaction mechanism. Dimethylsulfonium trimethylsilylmethylide (2), generated in situ from the corresponding sulfonium salt 1 with ec-butyllithium, reacts with various a,/l-unsaturated ketones to cyclopropanate the activated C-C double bond (see Table 2). The resulting l-acyl-2-trimethylsilylcyclopropanes 3 are isolated as mixtures of diastereomers. 

Michael-initiated ring closures (MIRC) offer an alternative strategy towards access of cyclopropane moieties. Compared to sulfur ylide-based approaches, MIRC affords greater flexibility as readily available all l halides can be used in conjunction with a,p-unsaturated aldehydes. However, such asymmetric ot-alkylation methods have suffered from undesirable side reactions and overalkylation. In 2007, the Wang group designed an MIRC... 

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