A dichotomy in the Friedel-Crafts reaction of lactones provides a convenient new route to 2-acylated pyrroles and tetrahydroindolones

Article abstract of DOI:10.1016/00404-0399(50)1328-F

In striking contrast to arenes, N-methylpyrrole undergoes Friedel-Crafts acylation with lactones. The reaction is most efficient with γ- and δ-lactones; ε-lactones proceed with poor overall conversion while β-lactones display poor selectivity. γ-Alkyl-γ-lactones readily yield 4,5,6,7-tetrahydroindol-7-ones through a sequence analogous to the Truce-Olson annulation.