SYNTHESIS OF NEW SULFUR HETEROAROMATICS ISOELECTRONIC WITH DIBENZO[G,P]CHRYSENE BY PHOTOCYCLIZATION OF THIENYL-SUBSTITUTED AND PHENYL-SUBSTITUTED ETHENES

A series of new sulfur heteroarenes, isoelectronic with dibenzo[g,p]ch rysene, have been prepared by double photocyclization of the correspon ding tetraaryl substituted ethenes. The first step proceeds efficientl y in each case, and the corresponding intermediate sulfur heteroarenes , isoelectronic with phenanthrene, have been isolated. The second ring closure is only efficient when one of the participating aryl substitu ents is thienyl, which thus manifests a higher electron density on the carbon atom involved in the excited singlet state reaction. Most of t he new compounds are of minimal solubility in common solvents and do n ot display improved electron donor properties otherwise commonly found among heteroaromatics.