title: A divergent and selective synthesis of isomeric benzoxazoles from a single N-Cl imine.
abstract: A divergent and regioselective synthesis of either 3-substituted benzisoxazoles or 2-substituted benzoxazoles from readily accessible ortho-hydroxyaryl N-H ketimines is described. The reaction proceeds in two distinct pathways through a common N-Cl imine intermediate: (a) N-O bond formation to form benzisoxazole under anhydrous conditions and (b) NaOCl mediated Beckmann-type rearrangement to form benzoxazole, respectively. The reaction path also depends on the electronic nature of the aromatic ring, with the electron-rich aromatic rings favoring the rearrangement and the electron-deficient rings favoring the N-O bond formation. A Beckmann-type rearrangement mechanism via net [1,2]-aryl migration for the formation of 2-substituted benzoxazole is proposed.
authors: Process Chemistry, Merck Research Laboratories, P.O. Box 2000, Rahway, New Jersey 07065, USA. cheng_chen@merck.com
authors: Cheng-yi
authors: CY
authors: Chen
authors: Teresa
authors: T
authors: Andreani
authors: Hongmei
authors: H
authors: Li
mesh_terms: D001583:Benzoxazoles / Q000138:chemical synthesis* / Q000737:chemistry; D003500:Cyclization; D007097:Imines / Q000737:chemistry*; D015394:Molecular Structure; D009570:Nitriles / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D001583:Benzoxazoles; D007097:Imines; D009570:Nitriles; C542835:ketimine