Butenolides formation from furans

Many examples of natural furans are recorded as having been prepared from five-membered heterocycles such as 2(5H)-furanones (butenolides), which are reduced to furans with diisobutylaluminum hydride. The facile elimination of selenoxides derived from a-phenylseleneyl-y-lactones with formation of endocyclic a,/3-unsaturated butenolides is reported (75JOC542) as a useful route to 2,4- and 2,3,4-substituted furans via their corresponding butenolides. The mixture of dihydrofurans obtained from the tosylhydrazone of tetrahydro-2-furanone (Scheme 88) was oxidized to furans by 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (66CJC1083). 

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