Epoxyannulation. 4. Reactions of 1,5-, 1,6-, and 1,7-Oxosulfonium Salts

Article abstract of DOI:10.1021/jo00149a003

Treatment of six 1,5- and 1,6-oxosulfonium salts with potassium tert-butoxide affords an oxabicyclo<3.1.0>hexane, an oxabicyclo<4.1.0>heptane, hydrindan oxides, or a decalin oxide in 55-95percent yield.The stereoselectivity of this reaction ranges from 75percent for the formation of (1α,3α,7α)-2-oxatricyclo<5.3.0.0^1,3>decane (21) to greater 99percent for (1α,2α,7α)-2-oxatricyclo<4.4.0.0^1,3>decane (14) and for (1α,2α,8β)-2-oxatricyclo<6.4.0.0^1,3>undecane (25).Five 1,7-oxosulfonium salts, one 1,8-salt, and one 1,11-salt and base give only elimination products.The sulfonium salt from 2-<3-methyl-5-(ethylthio)-2(Z)-pentenyl>cyclopentanone (29) provides 3-methylspiro<4.5>dec-2-en-6-one (30) in 40percent yield.The salt from 2-<3-methyl-5-(ethylthio)-2(Z)-pentenyl>cyclohexanone (32) yields 38percent of 4-methylbicyclo<5.4.0>undeca-1(7),3,5-triene (33).