73. “Reaction of the 5-Azoniafulvene Ion with Enamines: A New Approach to Pyrrolizines”
    Schärer, D.; Jindra, V.; Bringhen, A. O.; Burger, U.
    Helv. Chim. Acta 1991, 74, 1817-1822.

The synthesis of N,N-dimethyl-N-[(pyrro-1-yl)methyl]anilinium chloride (14) and of the corresponding p-toluidinium salt 15 is described. These salts, when dissolved in polar solvents, are shown to be in equilibrium with 1-(chloromethyl)pyrrole (17) and thereby potentially with the 5-azoniafulvene ion (2). Consequently, they react under very mild conditions (MeCN, 60°) with enamines to give pyrrolizine derivatives in acceptable yield (40–50°). The process is rationalized in terms of an initial Mannich-type reaction which is immediately followed by acyclization.

DOI : 10.1002/hlca.19910740824 

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