Pyrrolizidines Mannich cyclization

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. 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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