Synthesis of epoxides from carbonyl compounds and sulfonium salts

Synthesis of epoxides from carbonyl compounds and sulfonium salts 

Concentrated sulfuric arid (0.316 mol) was added over lh to dimethyl sulfide (0.316mol), the temperature of the reaction mixture being kept below 30°C. Methanol (0.156mol) was then added over 30min with the temperature below 35°C. After the mixture had been stirred for 5h, t-BuOH (0.048 mol) was added to it followed by potassium hydroxide (U.58 mol) in 10 equal aliquots over 2.5h. Benzaldehyde (O.lSmol) was added after the seventh KOH aliquot0 and an alkaline pH had been achieved. The mixture was stirred at room temperature for 12 h and subjected to conventional pentane/aqueous work-up. Styrene oxide was isolated in a 55% yield. 

The formation of an oxirane from the reaction of dimethylsulfonium methylidc with conjugated carbonyl compounds was applied to 

Q-thiomcthylcne ketones [452] in a pivotal step towards the synthesis of 3,4-substitutcd furans [453]. 

The reaction of a-oxoketene dithioacctals with dimethylsulfonium methylide led to another general route to furans and butenolides [454], according to the accompanying scheme. 

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