A New Synthesis of 2-[(Dialkylcarbamoyl)Methylene]Tetrahydrofuran Derivatives by Pd-Catalyzed Oxidative Aminocarbonylation of 4-yn-1-ols

A novel synthesis of 2-[(dialkylcarbamoyl)methylene]tetrahydrofuran derivatives 3-8 by Pd-catalyzed oxidative carbonylation of 4-yn-1-ols 1 in the presence of dialkylamines 2 is reported (2:1 molar ratio = 2). Reactions are carried out in 1,2- dimethoxyethane (DME) at 100°C and under 20 atm (at 25°C) of a 4:1 mixture of CO and air, in the presence of catalytic amounts of PdI2 (1 mol % with respect to 1) in conjunction with 10 equiv. of KI. Formation of 3-8 occurs through Pd-catalyzed oxidative monoaminocarbonylation of the triple bond of 1 to give 6-hydroxy-2-ynamide intermediates 9, followed by stereoselective conjugate addition of the hydroxyl group to the triple bond.