Photoinduced diastereoselective pinacolisation of 4-oxo-4-phenylbutanamides to 4,5-dihydroxy-4,5-diphenyloctanediamides

Abstract

The photoinduced pinacolisation of 4-oxo-4-phenylbutanamides 1 afforded 4,5-dihydroxy-4,5-diphenyloctanediamides 2 and 3 with unusual diastereoselectivities up to 83%, which depends on the amide substituent. In this reaction the solvent diethyl ether acts as a hydrogen donor. The structures of pinacols 2 and 3 were confirmed by X-ray analyses. Possible reasons for the diastereoselectivity and the preferred intermolecular hydrogen abstraction from the solvent are discussed. Products 5 and 6 obtained after irradiation of 4-oxo-4-phenylbutanoic acid 4 were identified by crystal structure determination as 2,2′-diphenyltetrahydro[2,2′]bifuranyl-5,5′-diones.