SYNTHESIS OF POLYCYCLIC 1,2-DIOXANES FROM ENDOPEROXIDES

1,4-Diphenylcyclohex-2-ene 1,4-endoperoxide (7) on catalysis with trim ethylsilyl trifluoromethanesulfonate (TMSOTf) in CH2Cl2, at -78 degree s C reacted partially with 1,4-diphenylcyclopenta-1,3-diene (5) to giv e ro-2,5a,8,9b-tetraphenyl-1H-4,d-dioxacyclopenta[a] naphthalene (8) i n 7.5% yield. Similar reaction of 1-phenylcyclohex-2-ene 1,4-endoperox ide (9) with 1-phenylcyclohexa-1,3-diene (10) afforded three 1,2-dioxa nes in a combined yield of 45%, one of which was identified as a,10b-o ctahydro-3,9-diphenyl-5,6-dioxaphenanthrene (11). The TMSOTf-catalysed reaction of 1,4-dihydro-1,4-dimethylnaphthalene 1,4-endoperoxide (12) with 1,4-diphenylcyclopenta-1,3-diene (5), benzofuran (14) and 1,1-di phenylethylene (16) gave the endo cis-fused tricyclic 1,2-dioxanes, (1 3), (15), and the cis-fused bicyclic 1,2-dioxane (17) as single produc ts in yields of 46, 81, and 72% respectively. The structures of 8, 11, 13, 15 and 17 were elucidated by X-Ray analysis.