Rac-BINOL

The idea of enantioselective activation was first reported by Mikami and Matsukawa111 for carbonyl-ene reactions. Using an additional catalytic amount of (R)-BINOL or (/ )-5.5 -dichloro-4,4, 6,fi -tctramcthyl biphenyl as the chiral activator, (R)-ene products were obtained in high ee when a catalyst system consisting of rac-BINOL and Ti(OPri)4 was employed for the enantioselective carbonyl ene reaction of glyoxylate (Scheme 8-54). Amazingly, racemic BINOL can also be used in this system as an activator for the (R)-BINOL-Ti catalyst, affording an enhanced level of enantioselectivity (96% ee). 

Marhwald reported that ligand exchange of Ti(rac-BINOLate)(Of-Bu)2 with optically active a-hydroxy acids presents an unexpected and novel approach to enantio-selective direct aldol reactions of aldehydes and ketones (Scheme 12.19). The aldol products have been isolated with a high degree of syn diastereoselectivity. High enantioselectivities have been observed when using simple optically pure a-hydroxy acids. 

The synthesis of BINAP has continued to evolve in search of more economical, easier and efficient procedures. Initially, Noyori and Takaya synthesized BINAP starting from rac-BINOL (3) by converting BINOL to the racemic dibromide 4 under forcing conditions. The corresponding dilithiated species (5) was then reacted with chlorodiphenylphosphine to obtain BINAP (6). Enantiomerically pure BINAP (la) was obtained via fractional crystallization of fhe Pd-complex (Scheme 1, 80JA7932). 

Among all catalysts containing phenol groups, the best results in terms of yields and asymmetric inductions were obtained with molecules containing a binaphthol scaffold. Inspired by the seminal work of Yamada et on the Morita-Baylis-Hillman reaction between cyclic enones and aldehydes promoted by a cooperative catalytic system of tributylphosphine and phenols (including rac-BINOL), McDougal and Schaus reported the first example of an asymmetric Morita-Baylis-Hillman reaction using chiral BINOL and binaphthol derivatives 38 as catalysts, in the presence of triethylphosphine as nucleophilic promoter (Scheme 24.15). 

Kantam, M. L., Arundhathi, R., Likhar, R R., and Damodara, D. 2009a. Reusable copper-aluminum hydrotalcite/rac-BINOL system for room temperature selective aerobic oxidation of alcohols. Arfv. Synth. Catal. 351(16) 2633-2637. 

Reaction conditions N -Dimethyl formamide, room temperature Synthetic strategy One-step amination via coupling reaction Catalyst CuBr, rac-BINOL (I) as ligand... 

Keywords Aryl iodides, aliphatic amines, CuBr, racemic-1,1 -binaphthyl-2,2 -diol (rac-BINOL), K3PO4, N,N-Dimethyl formamide (DMF), room temperature, coupling reaction, amination, N-arylation of aliphatic amines... 

In 2007, Fu reported room-temperature systems based either on iV-phenyl hydrazone (L19) or oti rac-BINOL (L20) (Scheme 6) [139, 140], These ligands, combined with Cul or CuBr (10 mol%), revealed good reactivity for the N-aiylation from aryl iodides of aliphatic amines and/or amino acids. 

The most frequently applied ligands are 2,2 -binaphthol (BINOL la) and 2,2 -bis(diphenyl-phosphino)binaphthyl (BINAP lb). Both antipodes of these compounds are commercially available in enantiopure form, though not at little cost [3]. It is rewarding, therefore, to become acquainted with the syntheses of these compounds, which have been described in detail [4J and have been simplified substantially on the basis of recent publications [5J. The iron(lIl)-catalyzed dimerization of 2-naphthol (2) to give racemic BINOL (rac)-la succeeds smoothly and on a large scale (Scheme 1). Its resolution can be achieved easily with N-benzylcinchoidinium chloride (3) and yields both (/ )- and (5 )-la in high enantiomeric excesses. After conversion into the ditri-flate 4, enantiopure la can be coupled with diphe-nylphosphine (or, in lower yield, with cheaper chlorodiphenylphosphine) in a nickel-catalyzed... 

When rac-(BIPHEP)PtCl2 was treated with Na2[(.S)-(BINOEate)], a kinetic 1 1 ratio of the (BINOLate)Pt(BIPHEP) diastereomers was isolated. Heating this mixture to92-122°C resulted in equilibration of the mixture to form a 95 5 ratio with the (5, 5)-diastereomer being thermodynamically favored (equation 4). Interconversion of the diastereomers likely proceeds by dissociation of a phosphorus from platinum, rotation, and recoordination. The minor (/ ,Y)-diastereomer was isolated cleanly by fractional precipitation. ... 

S)-Zr(EBTHI) complex. Thus, the recently developed procedure of Buchwald [22] is used to resolve rac-(EBTHI)Zr to obtain (R)-Zr(EBTHI)-binol and (S)-Zr(EBTHI)-biphen to accomplish this total synthesis in an efficient manner. 

Acocella et al. reported that, in tire presence of a phosphoric acid, rac-22b derived from racemic l,l -bi-2-naphthol (BINOL), the reaction of 2-silyloxyfuran 109b with nitroalkene 118 gave the VMM adduct 119 as a mixture of syn /anti-isomers in 82% yield (Scheme 50) [85]. 

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