Procedure:  500 mL 1-neck flask, stirbar, septum, N₂ inlet

                  Dissolved 7.0 mL of octyne (I) in 180 mL of dry THF.  Stirred;  cooled to -78 C.  Added 23.0 mL of n-BuLi (2.5 M in hexane).  The bath was removed and the reaction mixture was allowed to stir at rt for 30 min after which it was again cooled to -78 C.  Added 18.5 mL of DMF.  After 2 h the bath was removed and the reaction mixture was allowed to warm to rt.  The reaction mixture was quenched with sat. aq. NH₄Cl and extracted with hexanes.  The organic layer was dried over MgSO₄, filtered and the solvent was removed by rotary evaporation.  The product was isolated by Kugelrohr distillation (70 C, 0.5 mm).  The product was a clear, colorless oil. 

 

notes

 

In this reaction, the alkynyl anion adds to the carbonyl of DMF to give a stabilized lithium salt which eliminates dimethylamine upon exposure to acid during work-up.