Electrophilic cyclopropanes synthesis

This chapter will deal mainly with the synthesis and reactivity of electrophilic cyclopropanes and only these procedures and reactions will be investigated which give rise to cyclopropanes geminally substituted with two EWGs. Nevertheless, the preparation of monoactivated cyclopropanes will be mentioned to some extent because a number of procedures for the synthesis of electrophilic cyclopropanes have been developed for cyclopropanes bearing one EWG. Therefore, the synthesis and reactivity of the latter compounds cannot be excluded, due to the close relationship and the numerous studies concerning reaction mechanisms for these compounds. 

Synthesis and reactivity of electrophilic cyclopropanes b. MIRC reactions with the leaving group in the attacking nucleophile... 

Vinylsulphonium salts (375) are excellent precursors for the synthesis of electrophilic cyclopropanes via nucleophilic addition of active methylene functions followed by ring-closure (equation 123) . A similar reaction is observed using butadienylsulphonium... 

A general procedure for the preparation of electrophilic cyclopropanes consists of treatment of 1,2-dibromoethane with active methylene functions. In fact the first synthesis of an electrophilic cyclopropane, namely diethyl cyclopropane 1,1-dicar boxy late (equation 136), was performed using this reaction by Perkin in 1885 In this valuable method... 

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