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‐1 H ‐inden‐1‐one ( 5 ) is formed via a sulfur‐containing intermediate. Under phase‐transfer conditions [CH 3 N(C 8 H 17 ) 3 ] + [RhCl 4 (H 2 O) 2 ] − promotes reductive carbonylation of 1 to give initially the lactones 3,8‐dihydro‐ and 8,8a‐dihydro‐3‐phenyl‐8‐(phenylmethylene)‐2 H ‐indeno[2,1‐b]furan‐2‐one ( 6 and 7 ) which isomerize to 3‐phenyl‐8‐(phenylmethyl)‐2 H ‐indeno[2,1‐ b ]furan‐2‐one ( 8 ). Interaction of 1 and MeO 2 CC≡CCO 2 Me 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 H 2 PtCl 6 ‐Aliquat‐336 catalyst promotes the reaction of 1 with equimolar amounts of RO 2 CC≡CCO 2 R (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.