Enantioselective Suzuki Coupling

The yield for the chromium complex was lower, but the enantioselectivity was higher than for the corresponding ferrocene catalyst. 

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The asymmetric construction of axially chiral biaryl derivatives has been accomplished through enantioselective Suzuki coupling reactions, although... 

Enantioselective Suzuki coupling reactions that employ chiral catalysts for the synthesis of nonracemic biaryl derivatives have also been explored by several groups." The first examples of these transformations... 

Pu and co-workers incorporated atropisomeric binaphthols in polymer matrixes constituted of binaphthyl units, the macromolecular chiral ligands obtained being successfully used in numerous enantioselective metal-catalyzed reactions,97-99 such as asymmetric addition of dialkylzinc reagents to aldehydes.99 Recently, they also synthesized a stereoregular polymeric BINAP ligand by a Suzuki coupling of the (R)-BINAP oxide, followed by a reduction with trichlorosilane (Figure 10).100... 

In a related study, the Shibasaki group examined cyclizadon of naphthyl triflate 10.1 (Scheme 8G.10) [23], Cyclization of 10.1 under standard cationic conditions gave Heck product 10.2 in 78% yield and 87% ee. Evidently, the reaction is fairly tolerant of the nature of the aryl group, because both 10.1 and 9.3 behaved similarly. An interesting variation of this reaction was also demonstrated in which Suzuki coupling and asymmetric Heck cyclization were performed in a one-pot operation. Thus, treatment of ditriflate 10.3 with borane 10.4 under standard Heck conditions provided 10.2 in similar enantioselectivity to the stepwise procedure, albeit in quite low yield. Heck product 10.2 was converted in several steps to the natural products, halenaqui-none (10.5) and halenaquinol (10.6). 

Since many biaryls are chiral due to atropisomerism (see p. 147), the use of a chiral catalyst, and/or a chiral ligand can lead to enantioselectivity in the Suzuki coupling. ... 

The diastereoselective MesAI-mediated intramolecular Diels-Alder reaction, a highly ( )-selective Takai olefination and a Suzuki coupling were the key steps in the enantioselective total synthesis of (-)-equisetin by K. Shishido et al. It should be noted that the type of T-U olefination utilized allowed the preparation of functionalized heterosubstituted ( )-alkenes. 

Widdowson has exploited the asymmetric deprotonation of 183 in a synthesis of a protected version 191 of the biaryl component of vancomycin, actinoidinic acid (Scheme 48) [110, 111]. One of the rings derives from an arenechromiiun tricarbonyl with stereochemistry controlled by asymmetric lithiation. The most readily lithiated position of 183, between the two methoxy groups, first needed blocking. Enantioselective lithiation and chlorination of 184 gave 186 (TMEDA was needed to displace sparteine from 185 and restore reactivity towards a poor electrophile). Suzuki coupling of 187 with the boronic acid 188 transfers planar... 

A series of novel hydrophobic, bulky x Suzuki coupling of a-amino acid derivatives with boronic acids to afford these aromatic substituted amino acids in high yields and with high enantioselectivity (Equation 9) [10]. 

Scheme 7.8 Enantioselective synthesis of sertraline based on desynunetrization of oxabenzonorbomadiene 7 and Suzuki coupling to (R)-12...

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