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-5H-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 PdI2 in conjunction with 10 equiv. of KI. Formation of 3 occurs
Alkynols undergo palladium-catalyzed aminocarbonylation leading to the direct formation of different heterocyclic derivatives, depending on the position of the OH group with respect to the triple bond. In the cases of 4-yn-1-ols and (Z)-2-en-4-yn-1-ols, the initially formed 2-ynamide intermediates, respectively, undergo cyclization leading to tetrahydrofuran derivatives or 2-furan-2-ylacetamides, respectively. In the case of 2-yn-1-ols, the aminocarbonylation products undergo intermolecular conjugate addition, followed by lactonization, leading to aminofuranones.