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J Org Chem. 1999 Jan 08;64(1):93-100. doi: 10.1021/jo9811930.

Novel Asymmetric Synthesis of Atropisomeric 6-Aryl Pyrazinones via an Unusual Chirality Transfer Process.

The Journal of organic chemistry

John Tulinsky, B. Vernon Cheney, Stephen A. Mizsak, William Watt, Fusan Han, Lester A. Dolak, Thomas Judge, Ronald B. Gammill

Affiliations

  1. Structural, Analytical and Medicinal Chemistry, Pharmacia & Upjohn, Inc., Kalamazoo, Michigan 49001-0199.

PMID: 11674090 DOI: 10.1021/jo9811930

Abstract

Cyclization of (S,S)-alpha-[(1-phenylethyl)amino]-alpha-(2-iodophenyl)acetonitrile with (COCl)(2) in toluene or chlorobenzene afforded the atropisomeric pyrazinone (aS,S) 6-(2-alpha-iodophenyl)-3,5-dichloro-1-(1-phenylethyl)-2(1H)-pyrazinone in 57% yield. With smaller ortho substituents (F, Cl, CH(3), CF(3), OCH(3)) on the aromatic ring, mixtures of atropisomers were obtained from the cyclization reaction. All of the individual atropisomers prepared were stable at room temperature. All but the o-fluoro-substituted atropisomers were stable at elevated temperatures. This paper describes a stereoselective synthesis of pyrazinones and suggests a mechanism for formation via an interesting transfer of chirality.

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