Despite their extreme oxygen sensitivity, primary and secondary phosphines often react in a reliable and selective manner, making them crucial synthons to make new phosphine ligands. Alternative synthetic routes utilizing halophosphines often do not react in a selective manner. Although the chemical transformations to make phosphines have been known for the better part of a century, traditional reduction routes to yield phosphines on the gram scale (particularly volatile ones) are inadequate. Most reported methods suffer from poorly conceived or poorly described steps and use widely varying conditions that work in a substrate-controlled manner. A general procedure is presented for the facile reduction of phosphinates, phosphonates, and phosphine oxides to primary, secondary, and tertiary phosphines. The procedure is a methodical way to perform reductions to phosphines with a focus on valuable but extremely difficult-to-handle volatile phosphines. The challenges of volatile phosphine synthesis and handling will be discussed along with simple solutions to overcome them. Using this new unilateral procedure, gram scale reactions to synthesize primary, secondary, and tertiary phosphines are achieved reproducibly with excellent yields and purity.

Reduction of air-stable phosphine precursors and isolation of volatile 1°, 2°, and 3° phosphines on the gram scale

254th National Meeting (2017)

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