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-5Hfuran-2-ones 3 starting from very simple buildingblocks, i.e., -substituted 2-yn-1-ols 1, carbon monoxide,dialkylamines 2 and oxygen is reported.Reactions are carried out in 1,2-dimethoxyethane at100 C and under 20 atm (at 25 C) of a 4/1 mixture ofCO/air in the presence of catalytic amounts of PdI2 inconjunction with 10 equiv. of KI. Formation of 3occurs through an ordered sequence of steps, namely(a) Pd-catalyzed oxidative monoaminocarbonylationof 1 to give 4-hydroxy-2-ynamides 4, which can beisolated under appropriate conditions; (b) stereoselectiveconjugate addition of 2 to the triple bond of4, with formation of (not isolated) (E)-3-dialkylamino-4-hydroxy-2-enamides; (c) intramolecular alcoholysisof the amide function of the latter to give the finalproduct 3.