Ligand derivatives

Products from aminoalcohols and TYZOR TPT were obtained by a2eotropiag the isopropyl alcohol with ben2ene (121,122). From trimethylethylenediamine, dimethylethanolamine, and dimethylisopropanolamine with TYZOR TPT, the orange (11), the yellow (12), and the pale-green (13) were obtained, respectively. The lithium salt of the ligand, derived from C H Li, combiaed with (RO)2TiCl ia hexane has also been used (123). 

Montanari and his coworkers used the interesting polypode ligands derived from sym-trichlorotriazine as phase transfer catalysts for a variety of transformations. These catalysts were quite successful and their formation is illustrated below in Eqs. (7.3)— (7.5). Comparisons were also made with certain pentaerythrityl derived polypodes as well. These latter compounds are listed in Table 7.1 as compounds 10—13. 

Bis(amidinate) ligands derived from bulky terphenyl systems were prepared and used for the preparation of dialkylaluminum bis(amidinate) complexes In a... 

The chemoenzymatic synthesis of the analgesic U-(—)-50,488 [41] and new C2-symmetric bisaminoamide ligands derived from N,N-disubstituted trans-cyclohexane, ,2-diamine [41] has been possible by a CALB-catalyzed resolution using ethyl acetate as solvent and acyl donor [42]. 

Cobaltocene is partially oxidized and in part undergoes insertion of a borylene group, RB. The borinato ligands derive from the unknown borabenzene ( 6.5.3.4). Some porphyrinatoindium and thallium complexes ( 6.5.2.2) can also be synthesized via oxidative addition reactions (TPP)InCl is added oxidatively to Co2(CO)g and Mn2(CO) to give (TPP)In—Co(CO)4 and (TPP)ln — Mn(CO)j, respectively, and (oep)InCl is added to CojfCOg to yield (oep)ln— 0(00)4. 

Fig. 1.3 Various small-molecule peptoid ligands derived from combinatorial libraries...

FlCi. 1. / -donor ligand derivatives of ( + )-incntliylesler mcihylidync-capped clusters. 

Chelucci et al. [41] synthesized further chiral terpyridines derived from (-)-yd-pinene, (-i-)-camphor, and (-l-)-2-carene and tested their ability to chelate copper or rhodium for the asymmetric cyclopropanation of styrene. The copper catalysts were poorly efficient and selective in this reaction. The corresponding rhodium complexes led to the best result (64% ee) with the ligand derived from (-l-)-2-carene (ligand 33 in Scheme 17). 

These different catalysts were first tested in the desymmetrization of the achiral triene 63 (Scheme 40). The best enantioselectivities (up to 39%) were obtained with complexes 60b and 61c-d bearing carbene ligands derived from 1,2-diphenyl-1,2-diaminoethane (R = Ph). ligands derived from 1,2-diaminocyclohexane gave poor enantioselectivities (< 9% ee). Replacement of the mesityl group in complex 60b by o-methyl- or o-isopropylphenyl groups (complexes 61c-d) slightly increases the enantioselectivity (from 13... 

Ligand abbreviations bi = 2,2 -bi-2-imidazoline bt = 2,2 -bi-2-thiazoline bpy = 2,2 -bipyridine phen = 1,10-phenanthroline phy = l,10-phenanthroline-2-carbaldehyde phenylhydrazone bpp = 2,6-bis(pyrazol-3-yl)pyridine paptH = 2-(2-pyridylamino)-4-(2-pyridyl)thiazole 2-pic = 2-picolylamine L = macrocyclic ligand derived from condensation of 2,6-diacetylpyridine with 3,6-dioxaoctane-1,8-diamine Hjthpu = pyruvic acid thiosemicarbazone Hjthpx = pyridoxal thiosemicarbazone salen = dianion of W,iV -ethylenebis(salicylideneimine) H2fsa2en = dianion of fV,JV -ethylenebis(3-carboxysalicylaldimine). 

The test reaction was also investigated by Anderson et al. employing chiral imine-sulfide ligands derived from amino acids.The ligand of choice, depicted in Scheme 1.37, (S)-A-2 -chlorobenzylidene-2-amino-3-methyl-l-thiophenylbutane readily prepared from (5)-valinol, led to an enantioselectivity... 

A new class of easily accessible 1,2-disubstituted phosphinamidite-thioether ligands derived from Ugi s amine and based on a ferrocene motif has been... 

These reactions were also performed by Jin et al. in the presence of chiral amino thioaeetate ligands derived from (-i-)-norephedrine." As shown in Scheme 3.5, quantitative yields and excellent enantioselectivities of up to >99% ee were obtained in almost all eases of aldehydes, even when using 1.1 equivalent of ZnEt2 instead of 2 equivalents as usually employed. More recently, these authors developed eorresponding chiral amino thiocyanate derivatives from (-)-norephedrine and tested these new aprotic ligands for... 

In 2004, Yang and Tseng reported the synthesis of a series of new chiral amino thiols and corresponding amino thioacetate ligands derived from... 

In 1998, Anderson et al. developed a new series of S/N ligands derived from L-valine and analysed these in the enantioselective addition of ZnEt2 to aromatic aldehydes. The use of these ligands allowed enantioselectivities of up to 82% ee to be obtained (Scheme 3.10). The results showed that the ligands possessing symmetrical nitrogen substituents did not perform as well as those... 

In 2000, these workers described disulfonamide ligands derived from camphor, which could be easily prepared from chiral camphorsulfonyl chloride, and further successfully used in the enantioselective addition of ZnEt2 to... 

Among various amino alcohols used as ligands, derivatives of simple and easily available carbohydrates are only rarely reported and remain underestimated. In this context, a-hydroxy sulfonamides derived from D-glucosa-mine have been used by Bauer et al. for addition of ZnEt2 to aldehydes, providing the corresponding products in high enantioselectivities of up to 97% ee, as shown in Scheme 3.47. ... 

In 2003, these authors developed the Ti-catalysed enantioselective addition of ZnEt2 to benzaldehyde in the presence of C2-symmetric bis(camphorsulfo-namides) ligands derived from achiral 1,2- and 1,3-diamines and ( + )-camphorsulfonic acid. These authors showed that the stereochemical outcome of the reaction was highly influenced both by the structure of the... 

Similar reactions have been developed more recently by Jin et al. using chiral amino thioacetate ligands derived from the corresponding amino alcohols. Low catalyst loadings of only 1-2.5 mol% were sufficient to achieve excellent enantioselectivities of up to 98% ee as well as high conversions in short times (Scheme 3.61). These authors have shown that the thioacetoxy moiety of the amino thioacetates has a surprisingly beneficial effect in enhancing the asymmetric induction. 

In 2004, Yang and Tseng reported the synthesis of a series of new chiral amino thiol ligands derived from L-valine, which were further employed (1 mol%) in the enantioselective alkenylzinc addition to aldehydes, providing an efficient route for chiral ( )-allylic alcohols with enantioselectivities of up to >99% ee, as shown in Scheme 3.67. ... 

Scheme 6.18 Rh-catalysed cyclopropanation of styrene with sulfonamide ligands derived from aziridine- and azetidine-2-carboxylic acids.

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