Spiro-cyclopropanation from oxoallylsilanes.
A novel highly stereoselective spiro-cyclopropanation reaction from oxoallylsilanes is described. Oxoallylsilanes are readily obtained by silylcupration of allene followed by conjugate addition to enones. The former oxoallylsilanes undergo a tandem cyclization-cyclopropanation reaction when treated with CH2I2/Me3Al, leading to hydroxylated polycyclic systems bearing the spiro-cyclopropane moiety. The scope of the process is studied, and a feasible pathway is discussed.