Diastereoselective 1,3-dipolar cycloaddition of nitrones to donor-acceptor cyclopropanes catalyzed by a calcium(II) complex.

Calcium triflate has been identified as an efficient catalyst for the cycloaddition of nitrones to donor-acceptor cyclopropanes. The reaction proceeds with good to excellent yields of the corresponding tetrahydro-1,2-oxazines with high levels of diastereoselectivity. The generality of the reaction allowed for the synthesis of tetrahydro-1,2-oxazines bearing alkyl, aryl, and heteroaromatic substitution.