Metalation of N-Allenylpyrrole

Unlike N-vinylpyrrole, N-allenylpyrrole is selectively metalated with one equivalent of n-BuLi (THF/hexane, 10°C, 40 min) at the a-position of the allene 

SCHEME 2.220 2-Functionalized N-vinylpyrroles synthesized via metalation of N-vinylpyrroles and subsequent reactions of a-pyirole carbanion with electrophilies. 

Apart from lithium derivatives of N-allenylpyrrole, potassium, copper (1), and zinc derivatives have been tested in the reaction with trimethylchlorosilane. Copper and zinc compounds are easily prepared from organolithium ones by the exchange with the corresponding salts in THE Potassium derivatives (apparently. 

SCHEME 2.222 Lithiation of N-allenylpyrrole with exeess of -BuLi. 

SCHEME 2.223 Isomerization of the allenyl group to the propargylic moiety in the presence of -BuLi/f-BuOK system. 

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