Cycloadducts of Benzynes and 3,4-Dimethoxyfuran

Cycloaddition between benzyne and 3,4-dimethoxyfuran (1) yielded 2,3-dimethoxy-1,4-dihydro-1,4-epoxynaphthalene (3) which was unusually labile. On chromatography and exposure to air, it yielded (1 alpha,3 beta,4 alpha)-3-methoxy-3,4-dihydro-1,4-epoxynaphthalen-2(1H)-one (4) and (5 alpha,5a beta,6a alpha,7 beta,12 beta,12a alpha,13a beta,14 alpha)-6a,12a,13a-trimethoxy-6a,7,12,12a,13a,14-hexahydro-5,14:7,12-diepoxydinaphtho[2,3-b:2',3'-e][1,4]dioxin-5a(5H)-ol (19). A single-crystal X-ray structure determination was performed on compound (19). The chemistry of the ketone (4) was investigated. Cycloadditions were also carried out with 3,4-dimethoxyfuran (1) and methoxy-substituted benzynes. The regiochemistry of hydrolysis of the resultant adducts was explored.