THE SYNTHESIS OF BICYCLIC ORTHO-QUINODIMETHANES FROM TRICYCLIC SULFONES

The first synthesis of bicyclic ortho-quinodimethanes from tricyclic s ulfone precursors has been achieved. The required sulfones, trahydro-1 H-cyclohex[cd]benzothiophene-2,2-dioxide and -hexahydrocyclohept[cd]be nzothiophene-2,2-dioxide, were prepared from alpha-tetralone and benzo suberone utilizing a ring closure proceeding through a sulfonium salt intermediate. The same strategy failed when trying to prepare the tric yclic sulfone of the indane series. Other contrasting reactivity was a lso noticed when comparing the ability and ease of formation of tricyc lic ether compounds. These results indicate that the later ring system is considerably strained. (C) 1997 Elsevier Science Ltd.