T. Shimo et al., RING-TRANSFORMATION REACTIONS OF 5-HYDROXY-2-OXABICYCLO[3.2.0]-HEPTAN-4-ONES AND 5-HYDROXY-2-OXABICYCLO[3.2.0]HEPT-6-EN-4-ONES, Journal of heterocyclic chemistry, 34(2), 1997, pp. 533-536
Dehydrochlorination of chlorinated 5-hydroxy-2-oxabicyclo[3.2.0]heptan
-4-ones, 3a-c, which were obtained from the photo[2+2]cycloadditions b
etween 4-hydroxy-3(2H)-furanone 1 and chloroethylenes, with triethylam
ine gave 2-ethenyl-3(2H)-furanones 4a,b or 2-(2-cyanoethyl)-3(2H)-fura
none 4c. 2-Oxabicyclo[3.2.0]hept-6-en-4-ones 7 being [2+2]cycloadducts
between 1 and acetylenes gave 2,3-dihydro-3-oxooxepin derivatives 8 b
y electrocyclic rearrangement.