Synthesis of Acetylenic Amides with Propyllactam Moieties by In Situ DBU or DBN Ring-Opening Rearrangement in the Presence of Acetylenic Esters

DBN (1,5-diazabicyclo[4.3.0]non-5-ene) and DBU (1,8-diaza­bicyclo[5.4.0]undec-7-ene) react with methyl esters of acetylenic acids and excess water (the reactant molar ratio 1:1, in aqueous MeCN, at 20–25 °C, for 48 h) to afford acetylenic amides with pyrrolidone and caprolactam moieties in 89–100% yields. The synthesis involves amines formed in situ from the cyclic amidines, which further react with acetylenic esters.