Acta Crystallographica Section B

Structural Science

Volume 52, Part 6 (December 1996)

research papers

Acta Cryst. (1996). B52, 1007-1013 [ doi:10.1107/S0108768196009056 ]

Structures and photochemistry of dibenzobarrelene monoamides

R. Jones, A. G. M. Rattray, S. J. Rettig, J. R. Scheffer and J. Trotter

Abstract: The photochemistry of 9,10-ethenoanthracene-11-monoamides has been studied and correlated with the crystal structures determined for two derivatives; photoproduct structures have been established from a crystal structure analysis of one of the products and from NMR correlations. Crystal data are: (1)-Et, N, N-diethyl-9,10-dihydro-9,10-ethenoanthracene-11-carboxamide, C₂₁H₂₁NO, Pbca; (1)-Pr, 9,10-dihydro-N,N-di(isopropyl)-9,10-ethenoanthracene-11-carboxamide, C₂₃H₂₅NO, P2₁/c; (2 L)-Bz, 9,10-dihydro-9,10-ethenoanthracene-11-spiro-3'-(1-benzyl-4-phenylazetidine)-2'-one, C₃₁H₂₅NO (+ solvent), P2₁/a (Z = 8). The two dibenzobarrelene molecules have geometries and dimensions similar to those of related materials; the amide group in each molecule is only partially conjugated with the C 11=C 12 double bond. Mechanisms are derived for the formation of three types of photoproduct: (i) the well known di--methane reaction [(2M)-type photoproduct]; (ii) a hydrogen abstraction process (2H); (iii) -lactam formation (2 L).