Asymmetric synthesis, ligands for

Chiral carbenoid complexes with 2,2 -bipyridine ligands for asymmetric synthesis 98YGK764. 

Recently, the intramolecular nitrile oxide-alkene cycloaddition sequence was used to prepare spiro- w(isoxazolines), which are considered useful as chiral ligands for asymmetric synthesis (321). Reaction of the dibutenyl-dioxime (164) (derived from the diester 163) with sodium hypochlorite afforded a mixture of diastereomeric isoxazolines 165-167 in 74% combined yield (Scheme 6.80) (321). It was discovered that a catalytic amount of the Cu(II) complex 165-Cu(acac)2, where acac = acetylacetonate, significantly accelerated the reaction of diisopropylzinc... 

Since the discovery of cis-1 -amino-2-indanol as a ligand for human immunodeficiency virus protease inhibitors and the development of a practical industrial process for the synthesis of either ris-isomers in enantiopure form, the remarkable properties of the rigid indane platform have been used extensively in an ever-increasing number of asymmetric methodologies. In addition to the use of this amino alcohol as a chiral auxiliary and ligand for asymmetric synthesis, it has found application as a useful resolution agent. Applications include amines, carboxylic acids, and alcohols. 

Dr. Albert Padwa (Emory University) starts the volume with a fascinating chapter on the cycloaddition and cyclization chemistry of 2H-azirines, an area in which he has been closely connected with some of the most interesting developments. Dr. Nuzhat Arshad and Dr. Oliver Kappe of the University of Graz (Austria) update our knowledge of heterocyclic BINAP analogues, important ligands for asymmetric synthesis. 

Monosaccharides as Chiral Auxiliaries and Ligands for Asymmetric Synthesis... 

Metal phenoxides are utilized extensively in organic synthesis as reagents, since they can readily be prepared from phenols and appropriate metal reagents, and the phenol moiety can easily be modified either sterically or electronically. Particularly, 2,2 -dihydroxy-l,l -binaphthyl (BINOL), salicylideneamine and Af,Af -ethylenebis(salicylideneamine) (salen) proved to be excellent phenol ligands for asymmetric synthesis. Since some of their reactions have recently been reviewed , it may not be appropriate to reproduce all of them. Instead, this section concentrates on the effect of the phenol moiety on the chemical reactivity and selectivity, and tries to provide structure-activity relationships for the metal phenoxide reagents. Metalated derivatives of monophenols, biphenols and salicylaldehyde imines are discussed separately. 

Optically active bis(4,5-dihydrooxazoles), which are effective ligands for asymmetric synthesis (Section 3.04.12.5), have been prepared by zinc chloride-catalyzed coupling of amino alcohols and dinitriles <91CB1173> and by sodium hydroxide induced cyclization of bis(A-(2-chloroethyl)amides) <91JA728>. 

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