Catalysts aminophosphine

Agbossou E., Carpentier J. E. Hapiot E., Suisse I., Mortreux A. The Aminophos-phine-Phosphinites and Related Ligands Synthesis, Coordination Chemistry and Enantioselective Catalysis Coord. Chem. Rev. 1998 I78-I80 1615-1645 Keywords stereoselective Diels-Alder reaction catalysts, aminophosphine-phosphinites, enantioselective catalysts... 

This section essentially catalogs some of the newer catalyst systems that have not been considered in the previous sections. A number of the catalysts are certainly derived from more established ones (e.g., use of chelated aminophosphine ligand instead of two monodentate phosphines... 

BPPM Scheme 1.17) was used as catalyst [60]. The enantioselective hydrogenation of functionalized ketones was also efficiently achieved by a series of rhodium(I) aminophosphine- and amidophosphine-phosphinite complexes [61]. 

The beneficial effect of surfactants on enantioselective hydrogenations in water was exploited in the synthesis of a-aminophosphinic and a-aminophosphonic acids. These compounds are stmctural analogues of a-aminocarboxylic acids and their peptides find use as herbicides, bactericides and antibiotics [150,151]. With [Rh(BPPM)(COD)]Bp4 and similar catalysts fast ractions and e.e.-s up to 98% could be obtained in water in the presence of SDS (Scheme 3.12). 

In all but one case4 the enantiomeric excesses obtained in early work were modest, except when a range of aminophosphine ligands was employed 5-6. The resulting methodology is illustrated first by the derivation of a reactive catalyst precursor, and then by its application to the asymmet-... 

Palladium complexes generated from the sulfonated ligand 5 (Table 2 R=Me, n=0,l,2) were also used to catalyse the telomerization of 1,3-butadiene with water108 and from the aminophosphines 83 (Table 5 R=Ph R =H,Me R"=Me,iPr n=2,3) with MeOH to give l-methoxy-2,7-octadiene in selectivities up to 78% at conversions ranging from 52 to 80%.232 Pd/83 (R=Ph R =H,Me R"=Me,iPr n=2,3) catalysts are more active but less selective in the latter reaction compared to their tppts counterparts.232 9... 

Pt(II) complexes generally give hydroformylation products with higher asymmetric induction than Rh(I) complexes. A Pt(II)-SnCl2 complex with a chiral phosphine, aminophosphine, or phosphinite also catalyzes the hydroformylation of styrene in up to 86% optical yield (115). Stille noticed that the PtCl2(bppm)-SnCl2 combined catalyst is... 

This Mulheim chemistry has been highlighted by the discovery of the highly enantioselective hydrovinylation of styrene to produce chiral 2-phenyl-1-butene in 95.2% ee for a 10 kg-scale reaction (Scheme 60) (132). The Ni catalyst is very reactive and contains the unique chiral dimeric aminophosphine ligand derived from (R)-myrtenal and (S)-1-phenylethylamine. Computer simulations suggest that in this chiral Ni complex, the phenyl substituent of the chiral phenylethyl group acts as a windshield wiper across the catalytically active metal center. This... 

In an ESI-MS monitoring study of the Suzuki-Miyaura reaction using a dichloro-bis(aminophosphine) palladium precatalyst, binuclear Pd complexes were detected after the reaction went to completion, indicating a catalyst sink or a resting state. Addition of starting reagents resumes the reaction, suggesting the active role of the binuclear complex as a reservoir of mononuclear active catalyst. Other interpretations propose the involvement of Pd nanoparticles in which binuclear Pd complexes act as a precursor or perhaps even the active catalyst, but the last possibility seems unlikely. A mechanism for this transformation was proposed based on the intercepted species (Scheme 10) [62]. 

The catalyst derived from aminophosphine 4 enjoys very high reactivity and a similar substrate scope as ligand 3. In addition, mild bases could be employed in the arylation of dialkylamines [42, 43, 44]. With the catalyst derived from Pd2(dba)3 and 4, 4-bromomethylbenzoate reacted cleanly with morpholine in the presence of K3PO4, Eq. (14). With stronger bases such as NaOf-Bu, ester... 

Commercially available aminophosphine 4 provided even better yields in the coupHng of acycHc secondary amines [42]. The resulting catalyst was found to be so active that the reaction could often be conducted at room temperature. For example, Di- -butylamine was efficiently reacted with 4-bromotoluene in 96% isolated yield at room temperature, Eq. (27). In addition, electron-rich, electronically neutral, and electron-deficient aryl bromides were effectively utihzed with this new system. The 4/Pd-based catalysts also mediate the coupling of J -alkylanihnes that bear electron-donating substituents on the amine partner. A Xantphos/Pd-catalyst is effective in the coupling of electron-poor alkylaryl-amines with electron-poor aryl bromides. 

Aminophosphine 4 is an excellent supporting ligand in the room-temperature reaction of aryl bromides and primary amines [42]. The 4/Pd-catalyst is capable of coupling a hindered aryl bromide such as 2-bromo-raefa-xylene with -butylamine in excellent yield, Eq. (76). 

Kocovsky and co-workers reported the arylation of aminobinol mediated by a catalyst prepared from bulky aminophosphine 18 and Pd(dba)2 [97]. Complete conversion was observed in less than 5 minutes at 60 °C using the 18/Pd-system, Eq. (88) the BINAP/Pd-catalyst required 2 h for complete consumption of substrate under the same conditions. 

The catalyst derived from commercially available aminophosphine 4 is also mediates the desired reaction between chloroarenes and aniline derivatives, Eq. (108). Although the 4/Pd-system is effective for many applications, the 14/Pd-catalyst enjoys a similar substrate scope in the cross coupling reaction [42]. 

Scheme 7 displays a possibility of the synthesis of chiral 2-arylpropionic acids via the oxidative tranformation of (7 )-3-aryl-l-butenes. The requisite chiral olefins may be obtained by transition metal-catalyzed asymmetric coupling between a benzylic Grignard reagent and vinyl bromide (93 % optical yield) [28] or, more attractively, asymmetric hydrovinylation of an aromatic olefin with ethylene. The asymmetric combination of styrene and ethylene, giving the adduct 25 in 95 % ee, has been performed on a 10-kg scale with a dinuclear Ni catalyst formed from ( -allyl)NiCl2 and a unique chiral dimeric aminophosphine obtainable from (/ )-myrtenal and (5)-l-phenylethylamine [7a],... 

Very recently, Wang has prepared a new class of bis (aminophosphine) ligands 38 based on a new biphenyldiamine 4,4, 6,6 tetrakis trifluoromethyl biphenyl 2,2 diamine (TF BIPHAM) (Figure 9.8) [41]. These bis(aminophosphine) ligands ex hibited excellent to almost perfect enantioselectivities in the Rh catalyzed asymmet ric hydrogenation of enamides (97.6 99.9% ee) even at a catalyst loading ofO.l mol%. 

A novel class of complexes, Ir-(5 )-26a, with chiral spiro aminophosphine ligands was found to be effective catalyst for the asymmetric hydrogenation of a-substituted acrylic acids (Scheme 11) [62]. Under mild reaction conditions and at ambient pressure, various a-aryl and alkyl propionic acids were produced with extremely high efficiency (TONS up to 10 000 TOFs up to 6000h ) and excellent enantioselectivity (up to 99% ee). This reaction provides a practically useful method for the preparation of a-aryl propionic acids, a popular class of non-steroid anti-inflammtory reagents. 

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