Study on the reaction of phosphonates

Abstract

A method for the preparation of furylphosphonates has been developed starting with the addition of homoallylic phosphonates to nitrile, followed by a sequence consisting of acidic hydrolysis, iodine-mediated cyclization and dehydroiodination by DBU. β-Phosphonato-β,γ-unsaturated ketones have been prepared in high yields from iodocyclization of β-hydroxy phosphonates followed by treatment with t-BuOK. Treatment of lithiated homoallylic phosphonates with dimethyl carbamoyl chloride gave 2-amidophosphonate derivatives. A solution of 2-amidophosphonate in dimethoxy ethane DME-$H_2O$(2:1 vol) reacted with 2eq. iodine at room temperature to give α-phosphono-γ-iodoalkyl-γ-butyrolactones in good yield. We did not have to isolate the cis- and trans- isomers of dihydrofurans, because the stereoisomers afforded same α-methylene-γ-iodoalkyl-γ-substituted --butyrolactones by Horner-Emmons reaction. Reactions of the lithio anions derived from diethyl alkylphosphonates with phenyltellurenyl iodide gave diethyl 1-(phenyltelluro) alkylphosphonates. Diethyl 1-(alkyltelluro) phospho-nates were also prepared by the reaction of lithium tellurolates with iodomethylphosphonates. Reaction of α-lithio methylphosphonate with carbonyl compounds in THF followed by addition of diethyl chlorophosphate gave the phosphate derivatives. The phosphates were converted into the elimination product, vinylphosphonates, by treatment with t-BuOK in THF.