Stannyl cyclopropanes by diastereoselective cyclopropanations with(tributylstannyl)-diazoacetate esters catalyzed by Cu(I)N-heterocyclic carbene

摘要

Catalyzed cyclopropanations of alkenes with Bu_3SnC(=N_2)-CO_2R(R = Et,t-Bu)have been achieved in good yield with excellent diastereoselectivity to make stannyl cyclopropanes having two or three stereocenters,one of which is quaternary.Cyclopropylstannanes are useful building blocks for organic synthesis,with applications such as tin-lithium exchange reactions,tin-halogen exchanges,cross-couplings,and ring opening reactions.Methods of preparation that are summarized in a recent review include cyclopropanation of vinylstannanes,additions of tin compounds across the double bond of cyclopropenes and methylenecyclopropanes,among others.