A new method for the synthesis of heteroleptic alkylphosphine oxides from secondary phosphine oxides (SPOs) is presented. These reactions were fast at room temperature, sterically selective, high yielding, and &gt; 95% pure after an aqueous wash. Deprotonation of an SPO generates a phosphinite anion ([R2P-O]-) that was found to be highly selective for nucleophilic P-C bond formation (as opposed to O-C bond formation) with alkyl halides. Phosphinite anion reactivity followed the expected trend for an SN2 mechanism when reacted with alkyl halides; elimination products were never observed. Using this method, a wide variety of heteroleptic alkylphosphine oxides were isolated in near quantitative yield with only an aqueous wash as purification. This methodology provides facile access to air-stable heteroleptic tertiary phosphine oxides. The substrate scope and some mechanistic details will be presented, as well as subsequent reduction of phosphine oxides to phosphines.

Improved synthetic route to heteroleptic alkyl phosphine oxides and their reduction to phosphines

254th National Meeting (2017)

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