Facial diastereoselectivity in the [2+2]-photocycloaddition of N,N-diallyl amines

The stereoselective synthesis of 3-azabicyclo[3.2.0]heptanes 3, 4 and 7 by an intramolecular [2+2]-photocycloaddition is described. The facial diastereoselectivity of the reaction is low for methoxycarbonyl as the α-substituent. It is high if the α-substituent is connected to the nitrogen atom via an oxazolidinone ring. The photocycloaddition can be conducted as a triplet-sensitized reaction for the N-cinnamyl substituted substrates 2, 6a and 6b and as a Cu(OTf)₂-catalyzed process representing a more general method for the substrates 6a-6g.