Chromium and manganese carbonyl π-complexes of 2-benzylpyrrole and 2-phenylpyrrole. Spectra and electronic effects

The Direct Alkylation of π-Rich, Acid-Sensitive Heterocyclic Compounds via Essentially Free Carbocations1

“…1 H NMR spectra revealed that the reactions were complete. The observed product distributions were as follows: In pyrrole: 20% benzyl benzoate (δ 5.23), 50% 2-benzylpyrrole (δ 3.74),21a and 30% 3-benzylpyrrole (δ 3.71) 21a (Table ). In N -methylpyrrole: 32% benzyl benzoate, 33% 2-benzyl- N -methylpyrrole (δ 3.88),21b and 35% 3-benzyl- N -methylpyrrole (δ 3.80) 21c…”

“…The tube was cooled in liquid nitrogen and evacuated at oil pump pressure; it was sealed and incubated at 40 °C. Decomposition was complete in 3 days; the relative yields of products were 38% 2-benzylpyrrole (δ 3.74),21a 21% 3-benzylpyrrole (δ 3.71),21a and 41% benzyl benzoate (δ 5.22). The solution was divided into two parts, and one part was concentrated by evaporation of the solvent using a gentle stream of N 2 gas.…”

“…The chemical shifts thus obtained agreed very well with the literature values for the 2- and 3-benzylpyrroles in CCl 4 : δ obs for 2-benzylpyrrole = 3.77 (δ lit. = 3.78);21a δ obs for 3-benzylpyrrole = 3.73 (δ lit. = 3.70) 21a.…”

“…= 3.78);21a δ obs for 3-benzylpyrrole = 3.73 (δ lit. = 3.70) 21a. No N -benzylpyrrole was observed (absence of signal at δ 4.87) …”

A general method for the preparation of 2-benzylpyrroles by modified borohydride reduction of azafulvenium salts

“…Because of the efficiency of the reactions with lithium borohydride and sodium cyanoborohydride in THF these procedures were also applied to the preparation of the tetrasubstituted pyrroles (5e-h). The yields obtained [Table 6, entries [9][10][11][12][13][14][15][16] show an improvement on those obtained in the sodium borohydride-reduction in THF-ethyl acetate (Table 2). However, the yields are sufficiently high in the latter reaction for it to be satisfactory for use in large-scale preparations.…”