Metalation of N-Vinylpyrrole

9 Metalation of N-Vinylpyrroles and Their Analogs 2.2.9.1 Metalation of N-Vinylpyrrole 

If n-BuBr is used as an electrophile, the reaction affords the products of double alkylation, simultaneously at the vinyl group and the pyrrole ring. 

The double alkylation can be circumvented by adding twofold molar excess of LiBr to the metalating systan. Apparently, this shifts equilibrium between lithium aud potassium derivatives toward the former, which possess a weaker reactivity, and, therefore, ensmes higher selectivity relative to the electrophile attack. Under these conditions, the following electrophiles have been involved into the reactions methyl 

SCHEME 2.219 Metalation of N-vinylpyrrole with the n-BuLi/f-BuOK system. 

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

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