Photochemical formation of novel pyrrolo[3,2-b]-6,7-benzobicyclo[3.2.1]octa- 2,6-diene.

The first synthesis of 1,4,9,10-tetrahydro-4,9-methanobenzo[4,5]cyclohepta[1,2-b]pyrrole (11) was achieved by the photochemical intramolecular [2 + 2] cycloaddition of N-phenoxycarbonyl- (5a) and N-ethoxycarbonyl-2-[2-(2-vinylphenyl)]pyrrole (6a), respectively, followed by basic hydrolysis of the isolated N-substituted 1,4,9,10-tetrahydro-4,9-methanobenzo[4,5]cyclohepta[1,2-b]pyrroles (10a, 10b). Some competitively formed products were also isolated.