SOME UNUSUAL REACTIONS OF 1,2-BIS(PHENYLETHYNYL)BENZENE WITH SULFUR, CARBON-MONOXIDE AND ALKYL ACETYLENEDICARBOXYLATES

1,2-Bis(phenylethynyl)benzene (1) reacts with sulfur, carbon monoxide, and acetylenedicarboxylic esters to give unusual polycyclic products. Under exclusion of air 1 adds sulfur to give 6-phenylbenz[b]indeno[2,1-d]thiopyran (3b) and bis(6-phenylbenz[b]indeno[2,1-d]thiopyran-11-yl) disulfide (4). In the presence of air 3-benzoyl-2-phenyl-1H-inden-1-one (5) is formed via a sulfur-containing intermediate. Under phase-transfer conditions [CH3N(C8H17)3]+[RhCl4(H2O)2]- promotes reductive carbonylation of 1 to give initially the lactones 3,8-dihydro- and 8,8a-dihydro-3-phenyl-8-(phenylmethylene)-2H-indeno[2,1-b]furan-2-one (6 and 7) which isomerize to 3-phenyl-8-(phenylmethyl)-2H-indeno[2,1-b]furan-2-one (8). Interaction of 1 and MeO2CC = CCO2Me in the presence of the same rhodium catalyst results in crosscyclooligomerization in which tetramethyl 2-(phenylethynyl)-1,1':2',1"-terphenyl-3',4',5',6'-tetracarboxylate (9) is obtained. The H2PtCl6-Aliquat-336 catalyst promotes the reaction of 1 with equimolar amounts of RO2CC = CCO2R (R = Me, Et, Pr) to give the corresponding (Z)-2-(10-phenylindeno[2,1-a]inden-5-yl)-2-butendioates (11a-c). The structures of 3b, 4, 5, 8, and 11a have been determined by X-ray diffraction analyses. Possible routes for the transformation of 1 into the polycyclic products are discussed.