PREPARATION AND PYROLYSIS OF SOME BICYCLIC AND TRICYCLIC SULFONES DERIVED FROM PHOTOCHEMICAL [2-CYCLOADDITION OF 2,3-DIHYDROTHIOPHENE 1,1-DIOXIDE (2-SULFOLENE)(2])

Photochemical reaction of 2,3-dihydrothiophene 1,1-dioxide [2-sulfolen e] with maleic anhydride gives the [2 + 2] cycloadduct 8 and simple re actions of the anhydride function provide access to a wide range of ne w bi- and tri-cyclic sulfones 9-13 and 15-24 containing the novel 2-th iabicyclo[3.2.0]heptane 2,2-dioxide ring system. On pyrolysis these un dergo either cycloreversion with elimination of 2-sulfolene or in one case extrusion of ethene and SO2 to give the 1,3-diene. Oxidative bis- decarboxylation of the diacid from hydrolysis of 8 gives the new simpl e alkene sulfone 31. Pyrolysis of this results in loss of only SO2 to give cyclohexa-1,3-diene, but its epoxide 34 loses SO2 and ethene to a fford furan, thus making 31 a synthetic equivalent of cyclobutadiene.