Pyrroles Mannich-type condensations

The two C—C bond-forming reactions in the trimerization of pyrrole are thus seen to be Mannich-type condensations and find many simple analogies, the most relevant one being that used to prepare 2-2 -pyrrolidinylpyrrole (19)."... 

Quaternary anilinium salts (240), obtained from reaction of (pyrrol-l-yl)methanol and the appropriate aniline with trioctylphosphine, react in polar solvents via the azonia-fulvene ion (241) with enamines through a Mannich-type reaction followed by cyclization to give pyrrolizidines 242 and 243124. The ratio between the pyrrolizidines formed varies considerably with ring size of the enamine employed (equation 50). Pyrrolizines have also been obtained by reaction of pyrrole with two equivalents of enamine125 or condensation of some ketones with L-sodium or L-ethyl prolinate126. 

A pyrrol-fused azepine was formed under HAM conditions of Af-ethyl-AT-methallyl amine (Scheme 5.114) [83]. Individual steps are intramolecular HAM, Mannich-type aldol condensation to form the bicyclic skeleton, and final... 

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