Ferrocenylamines chiral

In mosl allylation reactions, only a catalytic amount of CuCN-2LiCl is required [41]. Use of die chiral ferrocenylamine 104 as a catalyst makes enables asymmetric allylation of diorganozinc reagents to be effected witli allylic chlorides iScbeme 2.3G) [78]. Related electropb des such as propargylic bromides [79] and unsaturated epoxides [80] also undergo Su2 -substitution reactions iScbeme 2.37). 

The sequence of Ugi-4CR + hydrolysis of the amino substituent has been employed in the stereoselective synthesis of chiral a-amino acid derivatives, by using a chiral amine component. Then the chiral template was covalently bound in close proximity to the newly synthesized chiral center. The amine residue of the product must be removable under mild conditions to avoid decomposition of the desired product. Chiral a-ferrocenylamines have been employed with some success [34], but the most useful auxiliaries were carbohydrate amines [35]. 

Ugi s ferrocenylamine has also been used in the synthesis of chiral biden-tate NHC heterodonor ligands in which the second ligating unit is either a diphenylphosphino or phenylsulfid group [89]. Several rhodium(I) and iridium complexes have been prepared which are depicted in Scheme 33. 

Chiral P-Hydroxy-a-Aminophosphonic Acids. An enan-tioselective synthesis of substituted dihydrooxazolin-4-yl phos-phonates was reported by the reaction of an aldehyde with a-isocyanomethylphosphonate ester catalyzed by (i )-(5)-(l) (eq 12). The enantiomeric purity of the product was determined by P H NMR spectroscopy using the chiral solvating reagent (.S)-(+)-2,2,2-trifluoro-l-(9-anthryl)ethanol. Independently, an asymmetric synthesis of ot-aminophosphonic acids was reported using the chiral ferrocenylamine catalyst (R)-(S)-(3) (eq 13). ... 

The reaction of chiral lithiated ferrocenylamines with dialkylthiuramdisulfides leads to the corresponding (dialkylthiocarbamoyl)thioferrocenes [144]. For catalytic applications, sulfur and selenium derivatives with one [140, 141, 145] or two [146—148] chalcogen substituents have been prepared (see Sect. 4.5.3.1). The technique is essentially the same as for the chiral phosphines lithiation of enantiomerically pure lV,iV-dimethyTl-ferrocenylethylamine, followed either by the addition of a disulfide or a diselenide to the monosubstituted compounds, or by... 

Soai and co-workers have continued their studies as described in two recent communications. One report details the synthesis of enantiomerically enriched ferrocenylamines by the catalytic, asymmetric dialkylzinc alkylation of a ferro-cenylimine [35b], and the other report introduces the use of heterogeneous chiral catalysts in the enantioselective diethylzinc alkylation of a phosphinoyl imine [35c]. 

In the previous section, three chiral reactions of rearrangements, Diels-Alder reactions, and Michael additions are shown in the presence of Pd, Pt, Rh, and Ru metal catalysts having arylamines, arylimines, aryloxazolines, ferrocenyloxazo-lines, ferrocenylimines, or ferrocenylamines as their substrates. 

Ugi has shown that chiral a-ferrocenylamines (78) provide products of moderate to excellent diastereoselectivity. However, harsh conditions (trifluoroacetic acid in methanol) are necessary for the removal of the chiral auxiliary from the product 79. This pitfall limits the applicability of this method in the presence of sensitive functionality. 

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