REACTION OF DIETHYL PHOSPHOROCHLORIDITE WITH ENOLATES - A GENERAL-METHOD FOR SYNTHESIS OF BETA-KETO PHOSPHONATES AND ALPHA-PHOSPHONO ESTERS THROUGH C-P BOND FORMATION

The reaction of ketone enolates with diethyl phosphorochloridite, followed by air oxidation of the immediate reaction products, has proven to be a general and convenient method for preparation of beta-keto phosphonates. Fourteen beta-keto phosphonates have been prepared by this method, in an average yield greater than 60%. This procedure also appears to be applicable to preparation of both alpha-phosphono aldehydes and alpha-phosphono esters. Although special precautions may be necessary to avoid aldol condensation during formation of aldehyde enolates, in two cases it was shown that the resulting enolates react readily with diethyl chlorophosphite. Finally, a set of five ethyl esters was converted to alpha-phosphono esters by this method. Yields of the alpha-phosphono esters are influenced by steric hindrance at the enolate carbon, but the average yield for this series was ca. 70%. Because this synthetic method relies upon an electrophilic phosphorus reagent for formation of the C-P bond, it is complementary to the traditional Arbuzov synthesis. On the basis of the 21 examples presented here, it appears to be more widely applicable.