One-Pot Synthesis of N-Acyl Indolines from 2-Aminophenethyl Alcohols

Significance

A concise one-pot synthesis of N-acyl indolines from the reaction of 2-amino­phenethyl alcohols with carboxylic acids utilizing PPh₃ and Et₃N is reported. The process is efficient, simple, and scalable. Most starting materials are commercially available or can be easily synthesized but it is a disappointment that the carcinogenic CCl₄ was used as the reaction medium. The yields range mostly from good to excellent, except for R² = CCl₃ for which the yield is only 40%. The substrate scope was sufficiently studied for the carboxylic acid reaction partner, but not for the amine. The synthesized indolines may be converted via oxidation into the biologically significant indoles and oxindoles (J. R. Dunetz, R. L. Danheiser J. Am. Chem. Soc. 2005, 127, 5776). The reaction is a modification of the Uneyama procedure (K. Uneyama and co-workersJ. Org. Chem. 1993, 58, 32) and proceeds through the formation of imidoyl chlorides followed by intramolecular cyclization.