| Abstract
| - The photochemistry of 13 4,4-diphenylcyclohexenones, substituted at carbon-6, was investigatedin solution and in the crystalline state. The stereoselectivity was of particular interest. In the solutionphotochemistry of C-6 monosubstituted enones in benzene, there was a unique preference formigration of the cis-phenyl group with formation of bicyclo[3.1.0]hexanone photoproducts, withthe original 6-substituent having an endo configuration at carbon-3 of the product. In methanolthe reaction was diverted to afford 3,4-diphenylcyclohex-2-enes understood as arising from ahydrogen-bonded zwitterionic intermediate. The solid-state photochemistry was also investigated.There was a dramatic absence of the 3,4-diphenylcyclohex-2-ene products in accord with the absenceof the hydrogen bonding encountered in methanol. Further, the solid-state reactivity correlatedwith a vector analysis using X-ray atomic coordinates. This established that the migrating phenylgroup required an orientation facing the enone β-carbon. While the interesting preference for thecis-endo migration was not intuitively predicted, ab initio computations on the alternative phenyl-bridged triplet intermediates did lead to an understanding of the selectivity.
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