The β-substitution of N-alkylpyrroles which is “unusual” but predicted by theoretical calculations, was supported by the 1H-NMR and GC/MS analysis of the reaction products of 1-methylpyrrole-2, 5-d2 (1a) with trimethylsilyl trifluoromethane-sulfonate (2) in triethylamine (3). Thus, 1a gives with 2 in 3 predominantly the β-isomer 5b (two deuteriums) and small amounts of the α-isomer 4a (one deuterium). The formation of these products of such a ...