Synthesis of benzimidazoles containing a fused alicyclic ring by Rhodium - catalysed hydroformylation of N-alkenyl-1,2-diaminobenzenes

Rhodium-catalysed reactions of N-alkenyl-1,2-diaminobenzenes(3) with hydrogen and carbon monoxide give benzimidazoles containing a fused alicyclic ring ((8) and (9)) in excellent yields. In some cases intermediate bicyclic compounds can be isolated and the ¹H and ¹³C n.m.r. spectra of one of these, the 3,4,5,6-tetrahydro-4-methyl-3H-1,6-benzodiazocine (6), shows evidence for unusual atropisomerism.