Application of 7‐ endo ‐ trig Pictet–Spengler Cyclization to the Formation of the Benzazepine Ring: Synthesis of Benzazepinoindoles

The preparation of benzazepinoindoles, fused heterocycles with a benzazepine moiety, was accomplished through an intramolecular 7‐ endo ‐ trig Pictet–Spengler cyclization. The precursors comprising C‐3‐ or C‐2‐linked o ‐aminobenzylindoles required for the cyclization were obtained either by treating indoles with o ‐nitrobenzyl bromide followed by reduction of the nitro group or by treating 2‐nitrophenylacetic acid with DCC/DMAP followed by reduction of the aryl nitro functionality. Resulting substrates 5 and 6 were then subjected to the 7‐ endo ‐ trig Pictet–Spengler reaction with a variety of aldehydes and ketones to furnish new polycyclic structures benzazepinoindoles. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)