Regioselective carbon-carbon bond formation in titanium mediated reaction of ethylmagnesium bromide with allylic alcohols and allylic ethers

In the presence of Ti(Oi-Pr)(4) reaction of EtMgBr with allylic alcohols an d allylic ethers affords the products of formal S(N)2' substitution of hydr oxy or alkoxy groups with ethyl groups in moderate to good yields and excel lent regioselectivity. The mechanism of the reaction includes the formation of titanacyclopropanes as the key organometallic intermediates. Promoting action of EtMgBr on the process of C-C bond formation in the transformation of titanacyclopropane-olefin complex 5 into the titanacyclopentane ate com plex 6 is proposed.