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One-Pot Synthesis of N-Acyl Indolines from 2-Aminophenethyl Alcohols
Z. Wang, W. Wan, H. Jiang, J. Hao*
Shanghai University and Shanghai Institute of Organic Chemistry, P. R. of China
23 January 2008 (online)
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.