The synthesis of hydroxy-methyl-enebisphosphonates (2a-c) by the addition of dialkyl phosphite to the carbonyl group of the corresponding α-oxophosphonate (1a-c) was studied under microwave irradiation (MW) and solventless conditions in the presence of dialkylamine as the catalyst. After optimization, products 2a and 2b were obtained selectively and in good yields avoiding the formation of the phosphonate-phosphate by-product (3a and 3b) that is the result ofa rearrangement. The MW-assisted synthesis ofhydroxybisphosphonates (2a and 2b) offers complete conversions and a chemoselectivity of 100% as compared to the not so efficient thermal reaction. At the same time, the phenyl-substituted methylenebis-phosphonate 2c could be obtained in only 75% selectivity.
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