Diastereoselectivity in the Paternò–Büchi reaction on furan derivatives

The reaction of benzoin, 4,4′-dimethoxybenzoin and benzoin ethyl ether with furan gave the corresponding adduct with high diastereoselectivity (71–100%). The diastereoselectivity was explained considering the relative stability of the biradical intermediates. Benzofuran reacts with (S)-1-methylpropylbenzoylformate to give the corresponding adduct with de = 58%. The diastereoselectivity was explained considering the relative stability of the biradical intermediates.