The Lewis acid mediated cyclization of epoxides with 1,3‐bis(trimethylsilyloxy)‐1,3‐butadienes, electroneutral equivalents of 1,3‐dicarbonyl dianions, results in the formation of 2‐alkylidenetetrahydrofurans with a great variety of substitution patterns and functional groups. This includes the synthesis of 2,3′‐bifuranylidenes and 7‐oxabicyclo[4.3.0]nonanes. The cyclization of dienes with functionalized epoxides containing base‐labile groups proceeds with good chemoselectivity. In all reactions, good regio‐ and E diastereoselectivities are observed. Based on the stereoselectivities observed for reactions of 1,2‐disubstituted epoxides, a working hypothesis for the mechanism of the reaction is suggested.

A new strategy for the synthesis of bicyclic gamma-alkylidenebutenolides, butenolide-medium ring ether hybrids, is reported which involves Me(3)SiOTf-catalyzed cyclization of 1, 3-bis(trimethylsilyloxy)-1,3-butadienes with oxalyl chloride, Mitsunobu reaction, and subsequent ring-closing metathesis.

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A new approach for the synthesis of gamma-alkylidenetetronic acids and esters is reported which involves Me3SiOTf-catalyzed, regio- and stereoselective cyclization of 4-alkoxy-1,3-bis(trimethylsilyloxy)-1,3-butadienes with oxalyl chloride. The alpha-hydroxy group of the butenolides is efficiently functionalized by palladium-catalyzed cross-coupling reactions via the corresponding enol triflates.

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