Expedient Synthesis of 4‐Dialkylamino‐5H‐furan‐2‐ones by One‐Pot Sequential Pd‐Catalyzed Oxidative Carbonylation of 2‐Yn‐1‐ols–Conjugate Addition‐Lactonization

A novel synthesis of 4‐dialkylamino‐5 H ‐furan‐2‐ones 3 starting from very simple building blocks, i.e., α‐substituted 2‐yn‐1‐ols 1 , carbon monoxide, dialkylamines 2 and oxygen is reported. Reactions are carried out in 1,2‐dimethoxyethane at 100 °C and under 20 atm (at 25 °C) of a 4/1 mixture of CO/air in the presence of catalytic amounts of PdI 2 in conjunction with 10 equiv. of KI. Formation of 3 occurs through an ordered sequence of steps, namely (a) Pd‐catalyzed oxidative monoaminocarbonylation of 1 to give 4‐hydroxy‐2‐ynamides 4 , which can be isolated under appropriate conditions; (b) stereoselective conjugate addition of 2 to the triple bond of 4 , with formation of (not isolated) ( E )‐3‐dialkylamino‐4‐hydroxy‐2‐enamides; (c) intramolecular alcoholysis of the amide function of the latter to give the final product 3 .