By elimination of selenoxides

Several cyclobutenes can be synthesized by elimination of selenoxides from the corresponding methyl- or phenylselanyl derivatives 58 or by elimination of dimethyl selenide from the corresponding selenonium salts 60. The results of these conversions are summarized in Table l.23 The cyclobutenes have been used as precursors for substituted butadienes.23... 

Alkyl a-(alkylsulphonyl)acrylates, which in many cases polymerize very readily, can be prepared in high yield by elimination of selenoxide e.g. Scheme 44). ... 

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