Reactions of (phenylethynyl)sulfones with tricyclo[4.1.0.02,7]heptanes

Methyl-, phenyl-, p-chlorophenyl-, and p-tolyl(phenylethynyl)sulfones under photochemical or thermal initiation add to the central bicyclobutane C1-C7 bond of 1-R(H, Me, Ph)-tricyclo[4.1.0.0(2,7)]heptanes anti-selectively, and form norpinic adducts containing a phenylethynyl group in a geminal to substituent R position, and an endo-oriented sulfonyl group in position 7. The corresponding ketones were prepared by the hydration of the anti-adducts by the method of Kucherov. The ketone with a methylsulfonyl substituent under reflux in toluene in the presence of KOH powder and the phase-transfer catalyst (TEBA-Cl) afforded the tricyclic sulfone.