Concise Construction of Bicyclo[6.4.0] and -[7.4.0] Frameworks by [4+2] Cycloaddition of 3,4-Dimethylene-2,5-bis(phenylsulfonyl) cycloalk-1-enes

摘要

The thermal intermolecular [4+2] cycloadditions of vicinal bis(exo-methylene)cyclooctene with carbon dienophiles efficiently produce the bicyclo[6.4.0] framework. Similar cycloadditions with the one-carbon-homologated cyclononene derivatives result in the formation of the bicyclo[7.4.0] skeleton. Both aza- and oxadieonphiles are suitable for this [4+2] reaction and provide the corresponding hetero-Diels-Alder-type products.