Some Unusual Reactions of 1,2‐Bis(phenylethynyl)benzene with Sulfur, Carbon Monoxide and Alkyl Acetylenedicarboxylates

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Abstract
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‐α]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.

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