2-ALKYNYLCYCLOPENT-2-ENOLS FROM 2-ALKYNYLCYCLOHEX-2-ENONES VIA 1-ALKYNYL-7-OXABICYCLO[4.1.0]HEPTAN-2-ONES

2-Alkynylcyclohex-2-enones 1a-c and 2a-c react with H2O2/NaOH in MeOH to afford 1-alkynyl-7-oxabicyclo[4.1.0]heptan-2-ones 3a-c and 4a-c, re spectively. The 3-unsubstituted bicyclic epoxy ketones 3a, 3b, and 4a, 4b react further with H2O2/NaOH, undergoing ring contraction and (for mal) decarbonylation to give 2-alkynylcyclopent-2-enols 5a, 5b, and 6a , 6b, respectively. Epoxy ketones 3 are also obtained under neutral co nditions on irradiation (lambda = 350 nm) of cyclohexenones 1 in air-s aturated benzene solution. Similarly, under neutral conditions oxo-cyc loalkenecarbonitriles 8 react (thermally) with H2O2 in MeCN to give th e oxabicyclic carbonitriles 9.