Direct Synthesis of Chiral Tertiary Diphosphines via Pd(II)-Catalyzed Asymmetric Hydrophosphination of Dienones

Palladium catalyzed asymmetric hydrophosphination of α,β- and α,β,γ,δ-unsaturated malonate esters – efficient control of reactivity, stereo- and regio-selectivity

A judicious choice of palladium catalysts and conditions afforded the hydrophosphination product in >99% regioselectivity (1,4- vs. 1,6-addition).

A one-pot diastereoselective self assembly of C-stereogenic copper(I) diphosphine clusters

C-chirogenic diphosphine-based clusters with 8-membered "chairlike" Cu4Cl4L2 and 12-membered "drumlike" Cu6Cl6L3 (L = diphosphine) frameworks were prepared in one-pot syntheses from chiral diphosphines, which were generated in situ via the double hydrophosphination reaction in excellent enantio- and diastereoselectivity. Excellent control over the final molecular architecture of the cluster (drum vs chair) could be achieved by the judicious selection of the source of the copper atoms employed in the synthetic protocol. Each cluster was characterized by single-crystal X-ray crystallography, (1)H, (13)C, and (31)P{(1)H} NMR spectroscopy. The synthesized clusters were found to exhibit catalytic activity in the hydroboration reaction of α,β-unsaturated enones with excellent yields albeit with low enantioselectivity.

PCN pincer palladium(II) complex catalyzed enantioselective hydrophosphination of enones: synthesis of pyridine-functionalized chiral phosphine oxides as NC(sp(3))O pincer preligands

A series of chiral PCN pincer Pd(II) complexes VI-XIII with aryl-based aminophosphine-imidazoline or phosphinite-imidazoline ligands were synthesized and characterized. They were examined as enantioselective catalysts for the hydrophosphination of enones. Among them, complex IX, which features a Ph2PO donor as well as an imidazoline donor with (4S)-phenyl and N-Tol-p groups, was found to be the optimal catalyst. Thus, in the presence of 2-5 mol % of complex IX a wide variety of enones reacted smoothly with diarylphosphines to give the corresponding chiral phosphine derivatives in high yields with enantioselectivities of up to 98% ee. In particular, heteroaryl species such as 2-thienyl-, 2-furyl-, and 2-pyridinyl-containing enones that have a strong coordination ability to the Pd center were also appropriate substrates for the current catalytic system. For example, hydrophosphination of 2-alkenoylpyridines with diphenylphosphine followed by oxidation with H2O2 afforded the corresponding pyridine-functionalized chiral phosphine oxides in good yields with good to excellent enantioselectivities (10 examples, up to 95% ee). Furthermore, it had been demonstrated that the obtained pyridine-containing phosphine oxide acted as a tridentate ligand in the reaction with PdCl2 to form an intriguing NCsp(3)O pincer Pd(II) complex via Csp(3)-H bond activation, which to our knowledge is the first example of a chiral DCsp(3)D' Pd pincer (D ≠ D'; D and D' denote donor atoms such as P, N, etc.).

Enantioselective phospha-Michael addition of diarylphosphines to β,γ-unsaturated α-ketoesters and amides

An enantioselective hydrophosphination of β,γ-unsaturated α-ketoesters and amides has been developed using a chiral palladacycle catalyst. Adducts can be obtained in excellent yields and enantioselectivities, providing direct access to chiral tertiary phosphines which are synthetically useful intermediates in the preparation of bidentate ligands.

Preparation of phosphines through C-P bond formation

Phosphines are an important class of ligands in the field of metal-catalysis. This has spurred the development of new routes toward functionalized phosphines. Some of the most important C–P bond formation strategies were reviewed and organized according to the hybridization of carbon in the newly formed C–P bond.

Stereogenic phosphorus-induced diastereoselective formation of chiral carbon during nucleophilic addition of chiral H-P species to aldehydes or ketones

P,C-stereogenic α-hydroxyl phosphinates or phosphine oxides were prepared from the additions of (RP)-phosphinate to ketones or (RP)-phosphine oxide to aldehydes, respectively, catalyzed by bases at room temperature in up to >99:1 diasteromeric ratio (d.r.P/d.r.C) and 99 % yields. The diastereoselectivity was induced by reversible equilibrium and different stabilities between two diastereomers of adduct, which was caused by the spatial interaction between menthoxyl or menthyl to alkyl groups of aldehydes or ketones.

Addition of optically pure H-phosphinate to ketones: selectivity, stereochemistry and mechanism

A stability-controlled diastereoselective addition of a chiral P–H species to ketones afforded P,C-stereogenic α-hydroxyphosphinates in excellent yields and dr.

Palladium-catalyzed 1,4-addition of secondary alkylphenylphosphines to α,β-unsaturated carbonyl compounds for the synthesis of phosphorus- and carbon-stereogenic compounds

Asymmetric 1,4-addition of alkylphenylphosphines to α,β-unsaturated carbonyl compounds catalyzed by pincer–Pd complexes is described to synthesize P-chiral compounds in high ee.

General and selective copper-catalyzed reduction of tertiary and secondary phosphine oxides: convenient synthesis of phosphines

Novel catalytic reductions of tertiary and secondary phosphine oxides to phosphines have been developed. Using tetramethyldisiloxane (TMDS) as a mild reducing agent in the presence of copper complexes, PO bonds are selectively reduced in the presence of other reducible functional groups (FGs) such as ketones, esters, and olefins. Based on this transformation, an efficient one pot reduction/phosphination domino sequence allows for the synthesis of a variety of functionalized aromatic and aliphatic phosphines in good yields.