Bifunctional phosphines

In the research aiming at the application of the addition reaction, Pringle and co-workers found that bifunctional phosphine starting materials like H2PCH2CH2PH2 spontaneously react with formaldehyde in the absence of the catalyst, forming water-soluble chelating phosphines [9]. 

Bifunctional phosphines also react forming chelating di-tertiary phosphines (Scheme 8). Serious catalysis inhibition by the product is not found. 

G-II), and (18-G-III) that are formed by bifunctional phosphines such as Ph2PCH2PPh2 or Ph l-pyridyl).1... 

S.D. Alexandratos, M.A. Strand, D.R. Quillen and A.J. Walder, Synthesis and characteristics of bifunctional phosphinic acid resins, Macromolecules, 1985, 18, 829 R.H. Selzer and D.G. Howery, Phosphoric acid ester cation-exchange resins. 1. Synthesis and preliminary characterization, Macromolecules, 1986, 19, 2673 Phos-phonic acid ester cation-exchange resins. 2. Physicochemical characterization, ibid. 1986, 19, 2974. 

Recently the problem of constructing bifunctional phosphine ligands with two different binding sites, each capable of bonding a different type of metal ion, has received attention. Two such ligands are 2(diphenylphos-... 

Most recently, a new bifunctional phosphine catalyst, (2 -hydroxybiphenyl-2-yl)-diphenylphosphane 225, has been developed for the selective aza-MBH reaction and aza-MBH domino reaction of iV-sulfonated imines with acrolein under mild conditions in moderate to excellent yields (Scheme 2.111). The possible catalytic cycle of the domino reaction and aza-MBH reaction has been proposed. The aza-MBH/Michael/aldol/dehydrate domino reaction also provides an efficient method to synthesize tetrahydropyridine... 

In 2003, we first demonstrated that l,l -bi-2,2 -naphthol (BINOL)-derived chiral LBBA (Lewis base and Bronsted add) bifunctional phosphine CP17 (LB = PPhs, BA = Ph-OH) could be used as an effective catalyst in asymmetric aza-MBH reaction of A-tosylimines with MVK and phenyl acrylate, affording the corresponding adducts in good yields with high ees (Scheme 2.119). The addition of molecular sieves increased chemical yields because they removed the ambient moisture that caused the decomposition of A-sulfonated imines. The asymmetric induction of this catalyst is comparable to that of the quinidine... 

As an efficient catalyst for enantioselective aza-MBH reaction, bifunctional phosphine catalyst CP17 has also been immobilized on a series of den-drimers. The dendrimer-immobilized catalyst CP44 was more effective than catalyst CP17 for the aza-MBH reaction of A-sulfonyl imines with MVK, EVK or acrolein. The catalyst could be separated easily from the reaction mixture by simple filtration after the reaction and reused without obvious loss of activity (Scheme 2.233). ... 

Subsequently, this significant capacity was exploited in metal-free hydrogenation procedures. First, Stephan and co-workers [16] reported that a structurally bifunctional phosphine-borane A can be used as a metal-free hydrogenation catalyst (Scheme 15.1) [16],... 

A series of bifunctional phosphine-sulfonamides have been developed as catalysts for the aza-MBH reactions. The threonine-derived candidate (200) turned out to be the most efficient (<97% ee) ... 

Synthesis of the molecular precursor complexes, Fe(CO)4L, NiL 4, trans-NiL 2Cl2, or Co2(CO)6L 2, and the associated bifunctional phosphine ligands, L or L, was accomplished using published procedures or procedures reported for the preparation of analogous complexes (5-9). 

Wolf, J., Labande, A., Daran, J.C. and Poli, R., Nickel(ll) conplexes with bifunctional phosphine-imidazolium ligands and their catal)4ic activity in the Kumada-Corriu coupling reaction, J. Organomet. Chem. 691 (3), 433 43 (2006). 

A review article by Blumel describes classical and modern solid-state NMR methods that allow to gain insight into catalyst systems where one or two metal complexes are bound to oxide supports via bifunctional phosphine linkers, such as (EtO)3Si(CH2)3PPh2. It has been shown that many aspects of the immobilized molecular catalysts can be elucidated with the corresponding NMR technique. For example, the bulk of the support can be studied, as well as the interface of the support with the ethoxysilane. In addition, electrostatic bonding to the support via phosphonium groups can be proven by solid-state NMR. For the immobilized catalysts, leaching, and even horizontal translational mobility effects, as probed by HR MAS NMR under realistic conditions in the presence of solvents, are described. 

Meng, X., Huang, Y., Chen, R. (2008). A novel selective aza-Morita-Bayhs-HiUman (aza-MBH) domino reaction and aza-MBH reaction of N-sulfonated imines with acrolein catalyzed by a bifunctional phosphine organocatalyst. Chemistry - A European Journal, 14, 6852-6856. 

D-Threonine-L-tert-leucine-derived bifunctional phosphine catalyzes highly enan-tioselective [3+2] annulation of maleimides with allenes, allowing the synthesis of optically active, functionalized bicyclic cyclopentenes containing two tertiary stereogenic centers (Scheme 6.30) [34],... 

For example, the first chiral phosphine-catalyzed [3+2] cycloaddition has been reported in 1997 by Zhang s group [95] (Schane 6.33A), and a variety of different chiral phosphine catalysts and apphcations thereof have been reported over the last years [94], Besides monofunctional catalysts, also bifunctional phosphines like the amino add-derived 197 have been successfully designed and apphed for challenging reactions recently [96], and this additional noncova-lent coordination site turned out to be highly beneficial to obtain good selectivities in these transformations. Chiral sulfides have emerged as powerful catalysts to facihtate catalytic stereoselective Corey-Chaykovsky-type epoxida-tion, cyclopropanation, or aziridination reactions (for an early example in this field, see Scheme 6.33C) [97,98],... 

Figure 31.3 Novel bifunctional phosphine-sulfonamide organic catalysts 143-148 derived from natural amino acids.

---