Methylphosphonic acid bis dimethylamide

Methylenation. This phosphonate ester is generally regarded as unsuitable for methylenation of ketones, even though the anion forms the intermediate adduct in satisfactory yield. However, under suitable experimental conditions, this reagent was used for methylenation of 1 to give 2 in 90% yield, higher than that obtained with methylphosphonic acid bis(dimethylamide) (78%).1 The optimum yield is obtained if exactly 2 equiv. of base and 1 equiv. of water are used to quench the adduct before cycloelimination. 

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