2,2′‐Bifurylidene‐5,5′‐diones, Coumarins, 3a, 7a‐dihydro‐1 H ‐inden‐1‐ones, and 5 H ‐furo[3,2‐ b ]pyran‐5‐ones from propyne and carbon monoxide

The [Co 2 (CO) 8 ]‐catalyzed reaction between propyne and CO in acetone at 110° and 170 bar was re‐investigated. There are five major products: ( E )‐3,4′‐dimethyl‐2,2′‐bifurylidene‐5,5′‐dione ( 4 ), 3,5,8‐trimethylcoumarin ( 8 ), 3a, 7a‐dihydro‐2,4,7,7a‐tetramethyl‐1 H ‐inden‐1‐one ( 9 ), 2,6‐dimethyl‐5 H ‐furo [3,2, ‐ b ]‐ pyran‐5‐one ( 11 ), and 2,7‐dimethyl‐5 H ‐furo 3,2‐ b ‐pyran‐5‐one ( 12 ); of these, only one, 4 . had previously been recognized. In parallel experiments were obtained 2,6‐dipentyl‐5 H ‐furo[3,2‐ b ]pyran‐5‐one ( 13 ), 2,7‐dipentyl–5 H ‐furo[3,2‐ b ]pyran‐5‐one ( 14 ), 3a, 7a‐dihydro‐2,4,7,7a‐tetrapentyl‐1 H ‐inden‐1‐one ( 15 ). And 3a, 7a‐dihydro‐2,4,6,7a‐tetrapentyl‐1 H ‐inden‐1‐one ( 16 ) from hept‐1‐yne, and two further types of products from two atypical 1‐alkynes: 3,6,9‐tri( tert ‐butyl)‐1‐oxaspiro[4.4]nona‐3,6,8‐trien‐2‐one ( 20 ) from ( tert ‐butyl)acetylene and the exo ‐dimer 21 of 2,5‐bis(trimethylsilyl)cyclopenta‐2,4‐dien‐1‐one ( 22 ) from (trimethylsilyl)acetylene. Compounds 11,12 , and 20 were identified by X‐ray analysis.