Carbonylation of alkynols catalyzed by Pd(II)/2-PyPPh2 dissolved in organic solvents and in ionic liquids: a facile entry to α-methylene γ- and δ-lactones

The carbonylation of terminal 3-alkyn-1-ols and 1-alkyn-4-ols by Pd(OAc)2 associated with 2-(diphenylphosphino)pyridine (2-PyPPh2) dissolved in organic solvents or in 1-n-butyl-3-methyl imidazolium ionic liquids affords quantitatively and selectively exo-α-methylene γ- and δ-lactones, respectively. In the case of the reactions performed in ionic liquids (biphasic conditions), the lactones were isolated by simple distillation and the ionic catalyst solution can be reused.