Isomerization, of unsaturated carbonyl compound

6-Dimethyl-2,4-cyclohexadienones 102 undergo photoisomerization to 103 by cleavage of the 1,6-bond from their n,Jt singlet excited states [59]. 

The isomerization is believed to take place by formation of a new o bond between C(2) and C(5), followed by formation of a zwitterion and its rearrangement. The resultant isomer undergoes nucleophilic addition of H2O and cleavage of cyclobutene ring to give 105. 

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