97130-17-1Relevant academic research and scientific papers
Diels-alder cycloadditions of 1,3,4,-oxadiazin-6-ones with electron rich pi systems
Padwa, Albert,Eisenbarth, Philipp
, p. 283 - 296 (2007/10/02)
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.
