| Abstract
| - Conjugate adducts obtained by base-induced 1,4-addition−elimination of various aryl/heteroarylacetonitriles with 1-(2-arylcyclopropyl)-3,3-(bismethylthio)-2-propen-1-ones have been shown toundergo facile acid-induced domino carbocationic rearrangement yielding a variety of substitutedtricyclic aromatic and heteroaromatic frameworks in high yields in a one-pot operation. Themethodology provides efficient, high-yield routes for synthesis of novel substituted dihydrophenalenes, dihydrobenzo[d,e]anthracene, cyclopenta[a]naphthalene, and fused heteroaromatics suchas substituted 4,5-dihydrobenzo[c,d]indole, dihydronaphtho[1,8-b,c]thiophene, dihydroindeno[5,4-b]- and -[4,5-b]-thiophenes, cyclopenta[a]carbazole, and dihydrocyclopenta[e]indazol-3-one derivatives. The probable mechanism of this interesting domino process appears to involve stepwise orconcomitant acid-induced ring opening and intramolecular cyclocondensation of cyclopropyl ketonesto give benzo-fused arene (or heteroarene) intermediates bearing a reactive benzylic carbocationthat is captured intramolecularly either by a preexisting aromatic (or heteroaromatic) ring or by anewly formed benzene ring to give either peri-fused or angularly fused products, respectively. Thus,the overall domino process entails formation of two C−C bonds, a substituted benzene ring alongwith a peri-fused cyclohexane or angularly fused cyclopentane ring in a single operation.
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