The reaction of trialkyl phosphites with monomethyl maleate at temperatures below 100" has been investigated and a mechanism has been suggested to account for the products of the reaction. Tetraalkylphosphonosuccinates were the main reaction product. Dialkyl maleates and/or fumarates, carbon dioxide, and trialkylphosphonopropionates were found in equivalent amounts as major by-products. Changes in the nature of the alkyl group of the ...