New Routes to Diethyl 1-Alkenylphosphoramidates

New routes to N-(diethoxyphosphoryl)imines derived from enolizable carbonyl compounds have been investigated. Three different procedures were studied: (i) the aza-Claisen condensation of ethyl-[N-(diethoxyphosphoryl)]-formimidate with enolizable ketones, (ii) the reaction between diethyl N-sulfinylphosphoramidate and aliphatic aldehydes, and (iii) the thermally induced reaction of diethyl phosphoramidate with ketone diethyl acetals. With two exceptions in all cases the products were identified as diethyl 1-alkenylphosphoramidates with no spectroscopically detectable amounts of imine tautomers. The aza-Claisen condensation can be recommended as a simple and effective route to diethyl 1-alkenyl-3-oxophosphoramidates.