Some reactions of an o-quinone monoimide with derivatives of furan and styrene†

Diels-Alder-type cycloaddition reactions occur across the heterodiene system of the o-quinone monoimide 1 when 1 is treated with the furans visnagin and 8-methoxypsoralen. Derivatives of a new heterocyclic system are formed. Similar cycloadditions take place between the heterodiene moiety of 1 and the olefinic linkages present in 7-methoxy-2,4-dimethyl-3-chromene (precocene I) and indene. In the former case another ring system previously uncharacterized was produced. Precocene I also reacted with o-chloranil and an o-quinone diimide to yield a benzopyrano[3,4-b] [1,4]benzodioxin and a benzopyrano[3,4-b]quinoxaline respectively.