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

Abstract

The iodocyclization of a series of alkenyl-substituted β-enamino esters and ketones, followed by base-promoted dehydroiodination, led to the formation of the corresponding pyrrole or tetrahydroindole derivatives. In the absence of base, the iodo-β-enamino esters 5 and 7 underwent spontaneous aromatization after dehydroiodination, furnishing the 4, 5, 6, 7-N-substituted-tetrahydroindoles 19 and 20. All the elimination reactions proceeded smoothly, in yields ranging from 71% to 99%. Starting from the β-allyl-dimedone 21, it was possible to prepare the oxotetrahydroindole 24, in moderate overall yield.