Tetrahedron p. 283 - 296 (1985)
Update date:2022-08-04
Topics: Diels-Alder cycloaddition 1,3,4-oxadiazin-6-ones Electron-rich pi systems
Padwa, Albert
Eisenbarth, Philipp
A study of the cycloaddition behavior of several 2,5-disubstituted 1,3,4-oxadiazin-6-ones with electron rich pi bonds has been carried out. trans-1-Propenylpyrrolidine was found to react with the oxadiazinone ring system to give rise to a ring opened diazatrienyl substituted carboxylic acid. Further heating of the acid results in decarboxylation, hydrolysis, cyclization and pyrrolidine elimination to produce a disubstituted pyrazole. Reaction with the trisubstituted enamine 1 - ( 2 - methyl-propenyl) pyrrolidine, was also studied in some detail. The cycloadditions encountered can be rationalized as proceeding by an initial Diels-Alder reaction followed by cheletropic extrusion of nitrogen to produce a ketoketene intermediate. The fate of the ketene is markedly dependent upon the overall pattern of substitution. Some of the products formed can be explained in terms of a competitive migration of the pyrrolidino group to the ketene and benzoyl groups. With one system the major cycloadduct is derived from the Diels-Alder reaction of a transient azaketene tautomer formed by an electrocyclic opening of the oxadiazinone ring.
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Doi:10.1021/jo00219a007
(1985)Doi:10.1016/S0040-4020(01)86134-2
(1988)Doi:10.1021/ol503437n
(2015)Doi:10.1039/c5ob00367a
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(1983)Doi:10.1021/ja01120a045
(1953)