Broken Promises? On the Continued Challenges Faced in Catalytic Hydrophosphination

Abstract

In this Perspective, we discuss what we perceive to be the continued challenges faced in catalytic hydrophosphination chemistry. Currently the literature is dominated by catalysts, many of which are highly effective, that generate the same phosphorus architectures, e.g., anti-Markovnikov products from the reaction of activated alkenes and alkynes with diarylphosphines. We highlight the state of the art in stereoselective hydrophosphination and the scope and limitations of chemoselective hydrophosphination with primary phosphines and PH₃. We also highlight the progress in the chemistry of the heavier homologues. In general, we have tried to emphasize what is missing from our hydrophosphination armament, with the aim of guiding future research targets.

Figure 1

Current challenges in catalytic hydrophosphination reactions.

Scheme 1. Divergent Regioselective HP of Terminal Alkynes with Phosphine-Boranes under Palladium Catalysis or Microwave Irradiation

Scheme 2. Divergent Regioselective HP of Styrene Derivatives with Ph₂PH Mediated by FeCl₂ and FeCl₃

Scheme 3. Divergent Regioselective HP of Terminal Alkynes with Ph₂PH in Different Solvents

Scheme 4. Intramolecular HP as a Strategy to Favor Markovnikov or Anti-Markovnikov Addition

Scheme 5. Sequential HP of 1,4-Pentadiene

Scheme 6. Cobalt-Catalyzed HP of Alkynes

Scheme 7. Asymmetric HP of Heterobicyclic Alkenes to Furnish Novel Chiral Phosphine Ligands

Scheme 8. Cu-Catalyzed Asymmetric HP of α,β-Unsaturated Amides

Scheme 9. Mn(I)-Catalyzed Asymmetric HP of Vinyl Nitriles and α,β-Unsaturated Nitriles

Scheme 10. Chemoselective Single Addition or Double Addition of RPH₂ to an Unsaturated Substrate to Furnish the 2° or 3° Phosphine, Respectively, versus Double Hydrophosphination

Scheme 11. (a) Chemoselective Formation of 2° Phosphine from Single Addition of PhPH₂ to Styrene Derivatives; (b) Sequential Single Addition of PhPH₂ to Internal Alkynes Followed by a Second HP with PhPH₂ to Furnish 1,2-Bis(phosphino) Substrates

Scheme 12. Single HP of Isocyanates and Carbodiimides

Scheme 13. (a) Regio- and Chemoselective HP of Styrene with PH₃ by Altering the Substrate:PH₃ Ratio; (b) Exclusive Formation of Tris(Z-styryl)phosphine from HP of Phenylacetylene with PH₃

Scheme 14. Hypothetical, Modular, and Effective Use of HP to Synthesize Highly Functionalized Bespoke Phosphines

Scheme 15. Analogous Pd-Catalyzed Hydrophosphination and Hydroarsination

Scheme 16. Catalyst-Free Hydrostibinations and an Arylbismuthation