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Note | Regular issue | Vol 68, No. 8, 2006, pp.1685-1689
Published online, 2nd June, 2006
DOI: 10.3987/COM-06-10737
Hetero-Diels-Alder Reaction of Ethyl 2-Nitrosoacrylate and Cyclohexadienes, and Bromine Induced Diene Isomerization

Jian Song, Yongcheng Lin,* Yau Shan Szeto, and Wing Lai Chan*

*School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, China

Abstract

Bicyclic 8a-methoxy-1,2-oxazine (3a) and bicyclic 7-methoxy-1,2-oxazine (3b) were prepared via Hetero-Diels-Alder reaction between 1-methoxy-1,4-cyclohexadiene (2a) and ethyl 2-nitrosoacrylate generated in situ from ethyl bromopyruvate oxime (1). The formation of 3b was ascribed to bromine, released from 1, which induced transformation of 2a to 1-methoxy-1,3-cyclohexadiene (2b). 3b could be easily transformed to oxazinone (3c) in CHCl3, or other organic solvents in the presence of a trace amount of acid.