Piloty-Robinson Synthesis

O. Piloty, Ber. 43, 489 (1910); G. M. Robinson, R. Robinson, J. Chem. Soc. 43, 639 (1918).

Formation of pyrroles by heating azines of enolizable ketones with acid catalysts, usually zinc chloride or hydrogen chloride:

Review: N. V. Sidgwick, Organic Chemistry of Nitrogen Compounds (Oxford, 3rd ed., 1966) pp 619-641; H. Posvic et al., J. Org. Chem. 39, 2575 (1974). Cf. Borsche-Drechsel Cyclization; Fischer Indole Synthesis.