N-Diphenylphosphinoyl

Aldehydes of MBH reactions can be replaced by activated aldimines such as N-tosyl, N-mesyl, N-nosyl, N-diphenylphosphinoyl, or N-SES aldimines. The addition of such aldimines to electron-deficient olefins can be mediated by nucleophilic tertiary N or P Lewis bases (Scheme 5.20). 

The most effective route to aminoalcohol (493) was established by screening various stereochemically homogeneous N,N-disubstituted-, N-monosubstitut-ed-amino alcohols and iminoalcohols as chiral additives to promote asymmetric addition of alkylzinc to N-diphenylphosphinoyl imine (492). The addition reactions that were performed in the presence of this compound resulted in excellent enantioselectivity (Figure 94a). 

Charette offers a way around some of these problems by demonstrating two alternative three-step methods. For aromatic aldehydes, an N-diphenylphosphinoyl imine can be preformed and isolated. Subsequent treatment with 2.0 equiv of Et2Zn in the presence of catalytic Cu(OT02... 

Finally, Elhnan has recently developed a method for the synthesis of a-aryl,-aryl substituted primary amines using the corresponding A-t-butanesulfmyl aldimine (chiral auxiliary approach) or via an N-diphenylphosphinoyl aldimine (catalytic enantioselective method) using an arylboronic acid in combination with chiral Rh catalysts. ... 

N-diphenylphosphinoyl imines also react with dialkylzinc in the presence of stoichiometric or catalytic amounts of different chiral see Chiral) ligands (Scheme 24). Acid hydrolysis of the resulting phosphinamides occurs without racemization and gives enantiomerically enriched primary amines. The allylation of various cyclic imines was obtained with high enantioselectivity seeElectrophile), 11 to 99% e.e., in the presence of lithiated bis-oxazoline ligands (Scheme 25). 

A diastereoselective approach to these chiral building blocks was developed by Ellman (Scheme 8.15) [40]. Thus, N-tert-butylsulfinyl aldimines 57 were employed as electrophiles in the rhodium/phosphine 58-catalyzed addition of arylboronic acids. Whereas Ellman s procedure requires heating, Batey discovered that an amine base allows the reaction to take place at ambient temperature [41]. However, it is worth noting that Ellman s process can also be carried out in an enantioselec-tive way by using N-diphenylphosphinoyl aldimines 48 as substrate and Degu-PHOS (56) as ligand (87-97% yield, 88-94% ee) (Scheme 8.14 Figure 8.4). 

The same type of olefination reaction has been carried out with N-diphenylphosphinoyl aldehyde 113 with chiral phosphonates of type 114 [74], The authors were interested in selective generation of the products and showed that a proper choice of reaction parameters (R group of the phosphonate, base and solvent) enabled the production of any one of the four possible stereoisomers as the major product... 

P ligand first by adding one C-NH bond in a reductive amination process, and then forming the second C=N bond and finally the third-generation complex 14 (Fig. 40). This new class of catalyst was effective in the rapid reduction of N-diphenylphosphinoyl-activated imines containing phosphinoyl groups in >99 % e.e. (Fig. 41) [126, 127]. 

Addition of lithiated alkoxy ethynyl anion with chiral Al-sulfinyl imines proceeds with dr >95 5, which can be reversed in the presence of BF3. Excellent diastereoselec-tivity has been reported for zinc-mediated addition of methyl and terminal alkynes to chiral IV-f-butanesulfinyl ketimines (to form 3-amino oxindoles). Zinc-BINOL complexes have been used to achieve enantioselective addition of terminal alkynes to N-(diphenylphosphinoyl)imines (up to 96% cc) and terminal 1,3-diynes to IV-arylimines to trifluoropyruvates (up to 97% yield and 97% ee). ... 

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