An improved synthesis of cyclic dialkynes

Article abstract of DOI:10.1055/s-1993-25901

An improved synthesis of 1,7-cyclododecadiyne 17 (35%), 1,7-cyclotridecadiyne 18 (65%), 1,8-cyclotetradecadiyne 19 (85%), 1,8-cyclopentadecadiyne 20 (65%), 1,9-cyclohexadecadiyne 21 (55%), 1,10-cyclooctadecadiyne 22 (48%) and 1,12-cyclodocosadiyne 23 (27%) is reported. This is achieved by treating the dilithium salts of diterminal dialkynes with α,ω-dihalogenides. As side products, tetraynes are isolated in yields of 1-5%. Furthermore, the synthesis of 6-isopropylidenethiacyclodeca-3,8-diyne (24) and [10]orthocyclophane-2,8-diyne 29 is reported. The reaction of 24 with CpCo(CO)₂ yields a [2.2](2,5)thiophenophane derivative 30 while 29 gives an intramolecular cyclobutadiene complex 31.