1-alkynylphosphines cycloaddition reactions

Cationic rhodium(I)/chiral biaryl bisphosphine complexes are suitable for the enantioselective [2-I-2-1-2] cycloaddition reactions between electron-rich alkynes and electron-deficient unsaturated compounds (alkynes, nitriles, and isocyanates). Alkynylcarbonyl compounds, alkynylphosphonates, and alkynylphosphine oxides are the best-suited electron-deficient unsaturated compounds for these catalysts. These complexes are also able to catalyze the highly enantioselective synthesis of axially chiral anilides and bezamides. 

Scheme 2.53 Rhodium-catalyzed formal [2-1-2- -2] cycloaddition reactions of 1-alkynylphosphine sulfides with tethered diynes.

Scheme 2.58 Enantioselective synthesis of P-stereogenic alkynylphosphine oxides by rhodium-catalyzed [24-24-2] cycloaddition reactions.

Kondoh, A., Yorimitsu, H. and Oshima, K. (2007) Synthesis of bulky phosphines by rhodium-catalyzed formal [2-1-2- -2] cycloaddition reactions of tethered diynes with 1-alkynylphosphine sulfides. Journal of the American Chemical Society, 129(22), 6996-6997. 

The syntheses of axially chiral biarylphosphine oxides based on alkynylphosphine oxide 2.157 and acetylene was carried out using chiral cobalt catalyst 2.159 [100, 105, 106]. The [24-24-2] cycloaddition, however, resulted in axially chiral biarylphosphine oxides 2.160 with moderate yield and enantioselectivity (Scheme 2.55). It was accompanied by a recovery of some of the corresponding phosphines. The newly obtained phosphines were used in the reaction of palladium-catalyzed hydrosilylation of unsymmetrical alkenes [100]. 

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