Synthesis of pyrazole-fused azepino[5,4,3-cd]indoles

The synthesis of some new pyrazolo[3',4':6,7]azepino[5,4,3-cd]indoles (10a- c) was achieved via regioselective cyclization of the respective 3-(4-acyla minopyrazol-5-yl)indoles (9a-c) under Bischler-Napieralski reaction conditi ons. The latter compounds were obtained by acylation of the corresponding 3 -(4-aminopyrazol-5-yl)indoles (8a,b) which, in turn, were prepared by reduc tion of the 3-(4-nitropyrazol-5-yl)indoles precursors (7a,b). The latter sy nthons were accessible from the reaction of indolylzinc chlorides (5a,b) wi th 5-chloro-1,3-dimethyl-4-nitropyrazole. Ms and nmr spectral data of 10a-c are in agreement with the assigned azepino-indole structure as determined for 10a by X-ray crystal measurements which demonstrate that the azepine ri ng is almost completely planar with the indole and pyrazole rings.