Synthesis of N-substituted pyrrole and tetrahydroindole derivatives from alkenyl beta-dicarbonyl compounds

The iodocyclization of a series of alknyl-substituted beta-enamino esters a nd ketones, followed by base-promoted dehydroiodination, led to the formati on of the corresponding pyrrole or tetrahydroindole derivatives. In the abs ence of base, the iodo-beta-enamino esters 5 and 7 underwent spontaneous ar omatization after dehydroiodination, furnishing the 4, 5, 6, 7-N-substitute d-tetrahydroindoles 19 and 20. All the elimination reactions proceeded smoo thly, in yields ranging from 71% to 99%. Starting from the beta-allyl-dimed one 21, it was possible to prepare the oxotetrahydroindole 24, in moderate overall yield. (C) 1999 Elsevier Science Ltd. All rights reserved.