New syntheses of arylphosphinic acids from the reaction of ethyl diethoxymethylphosphinate with aryl bromides and phenols

The chemistry of the hypophosphorous acid synthon, ethyl diethoxymethylphosphinate 1 has been further developed to afford efficient new routes to arylphosphinic acids 6 and 2-hydroxyphenylphosphinic acids 10. In one approach, a palladium(0) catalysed P–H insertion has been used; the second approach utilises a lithium-based ortho rearrangement of aryl phosphonates, readily prepared from the Atherton–Todd reaction of 1 with phenols. In both cases, the phosphinic acids were obtained in a final step by acid deprotection.