HETEROCYCLIC STUDIES .29. PHOTOISOMERIZATION OF 2,3-DIHYDRO-1,2-DIAZEPINE KETONES AND CARBINOLS TO 1,2-DIAZABICYCLO[3.2.0]-6-HEPTENES

Irradiation of the 2,3-dihydrodiazepinones (1) and the carbinols (3) gives in high yields the 1,2-diazabicyclo-[3.2.0]-6-hepten-4-ones (2) and -4-ols (4 and 5), respectively. The major photoalcohols in each case were shown by nmr analysis to be the exo isomers. The endo alcohols were the minor photoproducts of 3 and were obtained exclusively on reduction of the ketones (2) with NaBH4. The alcohols and tosylates are thermally stable, and elimination reactions have not been observed. Hydrogenation of derivatives of the endo alcohols gives mainly the endo-phenyldiazabicyclo[3.2.0]heptanols; in the exo alcohol series, equal amounts of exo- and endo-phenyl compounds are obtained. The rates of the photocyclization of the diazepinones (1) at 313 or 390 mμ decrease in the order R = CH3 ≅ CH2CH2CN > H >> COC6H5 ≅ COCH3. Under the same conditions at 313 mμ, the reverse order of substituent effects is obtained with the diazepinols 3: R = COCH3 ≅ COC6H5 > CH3 ≅ H. © 1968, American Chemical Society. All rights reserved.