SOLID-STATE AND SOLUTION PHOTOCHEMISTRY OF A 1-AZA DIENE

The N-acyl-2-cyano-1-aza diene 1 is photochemically reactive both in solution and in the solid state. Irradiation of 1 in solution produced a 98% yield of the bicyclo[3.1.0]hexene derivatives 2a and 2b. Irradiation of 1 in the solid state also produced the intramolecular reaction products 2a and 2b in 30% yield along with 65% of the intermolecular 2 + 2 cycloadduct 4. Inspection of the X-ray determined crystal structure of aza diene 1 suggests that the formation of the 2 + 2 cycloadduct in the solid state is primarily the result of topochemical control. The unusual occurrence of both unimolecular and bimolecular photoreactions provides the opportunity to obtain insight into the nature of the solid-state reaction. The ratios of the photoproducts (4 to 2a + 2b and 2a to 2b) under the various photochemical conditions are discussed in terms of the changing molecular environment of the solid-state photoreaction as a function of the reaction time.