BINAP 2? - -BINOL

A particularly important example is the 2,2 -diol, which is called BINOL. Another important type includes 1, I -binaphthyl diphosphines, such as BINAP. BINOL and BINAP are useful chiral ligands in organometallic compounds that serve as catalysts for hydrogenations and other reactions. In Section 2.5.1.1, we discuss how compounds such as BINOL and BINAP have been used to develop enantioselective hydrogenation catalysts. 

BBN AC2O AcOH AIBN BINAP BINOL Bn cHex Cp CSA DABCO DAST Pd2dba3 DBU DCC DDQ DEAD DIAD DIBALH Die DMAP DMB DMSO ED Cl HMPA HOBt Ipc... 

In a third form, the cross-coupling process forms a biaryl compoimd that possesses axial chirality as a result of slow atropisomerism (Equations 19.22 and 19.23). " In most cases, this reaction has been studied for the formation of 1,1 -binaphthyls (Equation 19.22), which are found in BINAP, BINOL, and related ligands. In a fourth form, ttie Heck reaction has been conducted in a manner that forms a product containing a new stereocenter (Equations 19.24-19.26). This type of enantioselective coupling has been the most widely used of the four in the synthesis of natural products. ... 

This (R)-polyBINAP support, when treated with [Rh(cod)2]BF4 or [ RuC12(C6H6) 2]. afforded a heterogeneous asymmetric catalyst for hydrogenation of dehydroaminoacid derivatives and ketones.100 As an extension, a copolymer with BINOL and BINAP units randomly distributed... 

The vast majority of successful chiral catalysts to date are based on tartaric acid, BINOL, or oxazolidinone derivatives (Table 26.1). Because derivatives of both of these compounds are commercially available, scale up should not present a problem. If the observed asymmetric induction is found to be low with catalysts based on tartaric acid or oxazolidinones, the sterically hindered titanium BINAP-type complexes should allow for increased selectivity. In addition, nontoxic metal counterions, such as iron and aluminum, do not appear to compromise the asymmetric induction. 

The enantiomeric atropoisomers of 1,1 -binaphthyl-2,2 -diol (BINOL) and bis-diphenylphosphonate derivatives (BINAP) are completely synthetic molecules that have been developed to exploit the axial dissymmetry induced by the restricted rotation about the biaryl bond (Scheme 1.8) [64]. During the past 15 years, these compounds have become the most widely used ligands for both stoichiometric and catalytic asymmetric reactions, with many analogues and derivatives having been developed recently. 

Chiral BINAP-and BINOL-Based Dendrimer Catalysts. 77... 

Let us consider as an example the synthesis of a precursor of the hydrogenation catalyst A -2,2 -biski iphenylphosphino)-1,1 -binaphthyl //-BINAP (Figure 5.59). The substrate of this reaction is enantiomerically pure A -l, l -bi-2-naphthol tA-BINOL). Its OH groups become... 

Fig. 5.59. Synthesis of a precursor of the hydrogenation catalyst fi-BINAP (for completion of its synthesis, see Figure 5.44) from fi-BINOL. Starting from enantiomerically pure BINOL the procedure presented here leads to dibromobinaph-thyl, also in racemic form—the reason is that the racemization threshold is crossed with such a high reaction temperature.

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