Scandium complexes amines

Additional catalytic investigation of p-diketiminate scandium complexes by Piers and coworkers showed that well-characterized complexes 121 and 122 with the bulky ligand L27 were highly active catalysts for intramolecular hydroamination to form nitrogen heterocycles. The catalytic reaction was monitored by determining starting material and product with NMR. Both the neutral complex 121 and the CIP complex 122 are effective catalysts (10 mol%) for the intramolecular hydroamination of 5-phenyl-4-pentyl-l-amine (R = H, R = Ph, n = 1 in Scheme 42). However, they are not active catalysts for the potential application to the intermolecular hydroamination of 1-hexyne with alkylamines [82],... 

Scandium complexes, 1059-1116 alkoxides, 1065 amides, 1062,1066 amine oxides, 1065 amines, 1060 amino acids, 1066 aromatic amines, 1061 arsenic compounds, 1065 2,2 -bipyridyl, 1061... 

Asymmetric 1,3-dipolar cycloaddition reaction of AT-benzylidenebenzyl-amine AT-oxide to 3-(( )-2-butenoyl)-l,3-oxazolidin-2-one was catalyzed by BlNOL-BOX-scandium complexes to give isoxazolidine in high yield with high enantioselectivity (111). La(lll)-aryloxide-PYBOX complexes were reported as enantioselective catalysts for direct Mannich-type reactions (112). 

Amine A-oxides, phosphine oxides and other phosphoryl compounds and analogous arsenic derivatives, and sulfoxides all give well-defined complexes with scandium. In many cases, authors deal with several of these classes of ligand in the same paper, so it will be most convenient to consider them together here. 

Kobayashi reported an asymmetric Diels-Alder reaction catalyzed by a chiral lanthanide(III) complex 24, prepared from ytterbium or scandium triflate [ Yb(OTf)3 or Sc(OTf)3], (Zf)-BINOL and tertiary amine (ex. 1,2,6-trimethylpiperidine) [30], A highly enantioselective and endose-lective Diels-Alder reaction of 3-(2-butenoyl)-l,3-oxazolidin-2-one (23) with cyclopentadiene (Scheme 9.13) takes place in the presence of 24. When chiral Sc catalyst 24a was used, asymmetric amplification was observed with regard to the enantiopurity of (/ )-BINOL and that of the endoadduct [31 ]. On the other hand, in the case of chiral Yb catalyst 24b, NLE was affected by additives, that is, when 3-acetyl-l,3-oxazolidin-2-one was added, almost no deviation was observed from linearity, whereas a negative NLE was observed with the addition of 3-pheny-lacetylacetone. 

CCC (1987) contains a section on sulfoxides, amide, amine oxides, and related ligands that have sections on phosphine oxides and arsine oxides.159 Phosphine and arsine oxide complexes of yttrium and the lanthanides were highlighted in CCC (1987).1 Scandium and yttrium phosphine oxide complexes have been reinvestigated and characterized by multinuclear NMR and X-ray... 

As for the chiral ytterbium and scandium catalysts, the following structures were postulated. The unique structure shown in scheme 13 was indicated by 13C NMR and IR spectra. The most characteristic point of the catalysts was the existence of hydrogen bonds between the phenolic hydrogens of (R)-binaphthol and the nitrogens of the tertiary amines. The 13 C NMR spectra indicated these interactions, and the existence of the hydrogen bonds was confirmed by the IR spectra (Fritsch and Zundel 1981). The coordination form of these catalysts may be similar to that of the lanthanide(III)-water or -alcohol complex (for a review see Hart 1987). It is noted that the structure is quite different from those of conventional chiral Lewis acids based on aluminum (Maruoka and Yamamoto 1989, Bao et al. 1993), boron (Hattori and Yamamoto 1992), or titanium... 

Although the transition states of the chiral lanthanide(III)-catalyzed reactions are rather complicated due to the specific coordination number and stereochemistry of the lanthanide(III), the sense of asymmetric induction in the chiral scandium-catalyzed reactions can be rationalized by assuming an intermediate octahedral Sc(III)-dienophile complex (scheme 14). The axial chirality of (R)-binaphthol is transferred to the amine,... 

The extraction coefficients of uivalent actinides, exuacted from concentrated chloride solutions, vary with the second power of total amine concentration and decrease with increasing aqueous acidity. A complex containing 2 molecules of trilaurylammoniumchloride per actinide is formed, which is in contrast to the 1 1 complex observed with iron under comparable conditions. Again, the decrease of the extraction coefficient as a function of acidity can be explained by competition between metal extraction and amine dihydrochloride formation. Actinide extraction decreases with temperature. Scandium and trivalent lanthanide extraction show approximately the same dependence on amine salt concentration and on acidity as the actinide extraction. The order of extractibility is... 

The first example of the use of rare earth metal complexes for asymmetric catalysis in organic solvents was reported in 1983 in chiral europium-catalyzed hetero Diels-Alder reactions. As for scandium catalysts, the first chiral catalyst was reported in 1994. Diels-Alder reactions using a chiral catalyst prepared from Sc(OTf)3, (/ )-BINOL, and an amine afforded the desired products in up to 97% ee. Following these results, many chiral rare earth metal catalysts have been developed. 

Catalytic enantioselective addition of amines to wiayo-epoxides can be realized by employing a scandium bipyridine complex in 100% water (Scheme 31). Chiral jS-amino alcohols were prepared in mostly high yields with excellent enantioselectivities (Scheme 31). It is noted that the use of water as a solvent gave a higher yield and enantioselec-tivity than the use of dichloromethane as a solvent. ... 

Kobayashi developed an operationally simple, enantioselective addition of aromatic amines to meso-epoxides using a scandium/chiral bipyridine complex in water so that /3-aminoalcohols could be obtained in high yields and with ee sup to 96% (Scheme 8.19). °... 

A. A/ -dioxide-scandium (II) complex (see Cat in Scheme 11.4), giving the corresponding chiral homoallylic amines 44 (67-89% yield) with excellent enantioselectivities (71-97% ee) [51]. 

Using same strategy, a catalytic, enantioselective addition of amines to meso-epoxides was established employing a scandium-bipyridine complex in emulsion (Scheme 8.12). In this work, Kobayashi and coworkers demonstrated that high yields and excellent enantioselectivities could be achieved using an amphiphilic Lewis acid combined with chiral Hgand as the catalyst in water. This work offered a green method for the synthesis of a-amino alcohols, which are important... 

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