Reactions of Furanylalkenes with Bromine in a Methylene Chloride–Aqueous Sodium Acetate System

Abstract

In this work, 3-(furan-2-yl) acrylates and 1-acyl-2-(furan-2-yl)ethylenes containing a tert-butyl substituent in position 5 of the furan ring, as well as their analogs in which the diethoxyphosphoryl group is located at the same atom of the alkene fragment as the furan fragment, were obtained. Furyl phosphonates containing an adamantan-1-yl substituent in position 5 of the furane ring were also synthesized. All the prepared compounds were studied in the reaction with bromine in the methylene chloride–aqueous sodium acetate system. Furanyl alkenes without phosphorus formed 2-bromo-3-(furan-2-yl) acrylates and 1-acyl-1-bromo-2-(furan-2-yl)ethylenes, respectively. Phosphorylated furanyl acrylates were converted to (2E,5E)-3-(diethoxyphosphoryl)-7-R-4,7-dioxohepta-2,5-dienoates. When treated with hydrazine hydrate in ethanol, they underwent cyclization to 2-substituted 5-(diethoxyphosphoryl)-3a-methyl-4-oxo-3a,4,5,6-tetrahydro-3H-pyrrolo[1,2-b]pyrazole-6-carboxylates, phosphorylated aza-analogues of pyrrolizidine alkaloids. 1-Acyl-2-(furan-2-yl)-2-(diethoxyphosphoryl)ethylenes reacted with bromine to give diethyl [7-R-2,7-dihydroxy-2,9-dimethyl-1,6-dioxaspiro[4,4]nona-3,8-dien-4-yl]phosphonates.