Cyclopropanation sequential Michael ring closure

The products obtained from the reaction of (chloromethyl)trimethylsilane with organolithium reagents depend very much on the structure of the lithium compound. While lithium 2,2,6,6-tetramethylpiperidide initiates an a-elimination as described above, the treatment with sec-butyllithium leads to the formation of chloro(trimethylsilyl)methyllithium (11). This reagent cyclopropanates an electron-deficient alkene through sequential Michael addition and intramolecular ring closure (MIRC reaction), for example, the formation of cyclopropane 12. 

Silicon-substituted cyclopropanes can also be generated by the reaction of electron-deficient alkenes with silyl-substituted carbanions bearing a leaving group. This transformation proceeds via sequential Michael addition and intramolecular ring closure (MIRC reaction). 

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