Cycloaddition between 2,3-dibromo-5,6-trinorbornenobenzoquinone and 1,2-bis(methoxycarbonyl)cyclobutadiene: intervention of a fragmentation reaction during quest for annulated, functionalized cubanes
Abstract
Diets–Alder reaction between 1,2-bis(methoxycarbonyl)cyclobutadiene 2 and quinone 1 predominantly furnished adduct 5, which on photolysis gave the annulated secopentaprismane dione 3. Attempted double-ring-contraction on compound 3 took a devious course to furnish a fragmentation product 11via tandem Haller–Bauer cleavage and fragmentation.