STRUCTURES AND PHOTOCHEMISTRY OF DIBENZOBARRELENE MONOAMIDES

The photochemistry of 9,10-ethenoanthracene-11-monoamides has been stu died and correlated with the crystal structures determined for two der ivatives; photoproduct structures have been established from a crystal structure analysis of one of the products and from NMR correlations. Crystal data are: (1)-Et, 9,10-dihydro-9,10-ethenoanthracene-11-carbox amide, C21H21NO, Pbca; (1)-Pr, 9,10-dihydro-N,N-di(isopropyl)-9, 10-et henoanthracene-11-carboxamide, C23H25NO, P2(1)/c; (2L)-Bz, e-11-spiro- 3'-(1-benzyl-4-phenylazetidine)-2'-one, C31H25NO (+ solvent), P2(1)/a (Z = 8). The two dibenzobarrelene molecules have geometries and dimens ions similar to those of related materials; the amide group in each mo lecule is only partially conjugated with the C11=C12 double bond. Mech anism are derived for the formation of three types of photoproduct: (i ) the well known di-pi-methane reaction [(2M)-type photoproduct]; (ii) a hydrogen abstraction process (2H); (iii) beta-lactam formation (2L) .