Abstract
A simple and general protocol for the catalytic homoallyl- and homocrotylation of aldehydes is described. Cyclopropanated allylboron reagents react with aldehydes in the presence of catalytic B(OTFA)3 to yield homoallylic products. Cyclopropanated cis- and trans-crotyl reagents afford the corresponding 1,3-anti- and 1,3-syn-methylsubstituted homocrotylated alcohols with high selectivity. NMR suggests the active species may be cyclopropylcarbinyl bis(trifluoroacetate) generated by trifluoroacetate exchange with the B(OTFA)3 catalyst.