Intramolecular C-O Bond-forming Reactions

Tetrahydropyran- and tetrahydrofuran-substituted rings are common in many complex natural products, such as polyether antibiotics, displaying a wide range of biological properties [4]. An appropriate combination of OH-directed diastereose-lective epoxidation of y- and 8-alkenols [VO(acac)2/TBHP or MCPBA] [5] or ster- 

Aziridines and Epoxides in Organic Synthesis. Andrei K. Yudin Copyright 2006 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 3-527-31213-7 

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As with the synthesis of benzofurans, the use of catalytic intramolecular C—O bond forming reactions has proved to be a popular route to benzoxazoles. Evindar, Batey and co-workers reported a copper-catalyzed cyclization of o-bromobenzanilides to generate a variety of 2-substituted benzoxazoles (Scheme 24.34) [123]. A number of similar cyclizations have also been reported [63,124,125]. 

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