BINAP.AgF

BINAP-AgF gives good enantioselectivity, especially for the major anti product in the addition of 2-butenylstannanes to benzaldehyde.188 This system appears to be stereoconvergent, suggesting that isomerization of the 2-butenyl system occurs, perhaps by transmetallation. 

The complex -Tol-BINAP-AgF (/>-Tol-BINAP - 2,2 -bis(di-/)-tolylphosphanyl)-l,l -binapthyl) catalyzes the asymmetric addition of allylic trimethoxysilanes to aldehydes (Equation (7)).7 3 The process can provide various optically active homoallylic alcohols with high enantioselectivity (up to 96% ee) and a remarkable 7 and anti- selectivities are observed for the reaction with crotylsilanes, irrespective of the configuration of the double bond ... 

Independently, Yamamoto, Yanagisawa, and others reported the asymmetric aldol reaction using trimethoxysilyl enol ethers.19 The reaction was conducted with aldehydes and trimethoxysilyl enol ethers in the presence of Tol-BINAP-AgF to give the corresponding adducts with high enantioselectivities and diastereoselectiv-ities. They obtained vyra-aldol adducts as major products even when silyl enol ethers derived from cyclic ketones were used. Moreover, when a,(3-unsaturated aldehydes were employed as substrates, 1,2 adducts were obtained exclusively (Table 9.10). From an NMR study and correlation between the E Z ratio of the enol ethers and diastereoselectiviy, they proposed a cyclic transition state (Fig. 9.5). Thus, the reaction of E enol ethers proceeded via a boat form, whereas the reaction of Z enol ethers took place via a chair form. 

As shown in Scheme 10.132 (Section 10.3.1.2), Yamamoto et al. have recently reported highly enantioselective allylation of aromatic and a, -unsaturated aldehydes with allyltrimethoxysilane using (P)-(p-Tol-)BINAP AgF as catalyst [377]. Shibasaki et al., on the other hand, have succeeded in asymmetric allylation of acetophenone with allyltrimethoxysilane by use of a p-Tol-BINAP CuCl-TBAT co-catalyst system (up to 61% ee) [378]. 

Table 18.1 Enantioselective allylation of aldehydes with al-lyltrimethoxysilane (27) catalyzed by (R)-/ -Tol-BINAP- AgF complex. ...

In contrast, Yanagisawa, Yamamoto, and coworkers have studied diverse combinations of BINAP-silver(I) catalysts and silyl enolates and found that high levels of asymmetric induction and isolated product yields were attained in the p-Tol-BINAP-AgF-catalyzed aldol reaction of trimethoxysilyl enolates (38) with aldehydes (39) in methanol (Scheme 18.15) [54]. Table 18.2 summarizes the results... 

Table 18.2 Diastereo- and enantioselective aldol reaction of trimethoxysilyl enolates (38) with aldehydes (39) catalyzed by (R)-/9-ToI-BINAP- AgF Complex.

Catalytic enantioselective protonation of prochiral ketone enolates is a beneficial route to optically active carbonyl compounds possessing a tertiary asymmetric carbon at the a-position. In the asymmetric protonation of trimethylsilyl enolates with methanol, BINAP-AgF has been found to act as a chiral catalyst [90,91], which is also known to catalyze asymmetric allylation of aldehydes with allylic trimethoxysilanes [42] as well as asymmetric aldol reaction with trimethoxysilyl enolates [54]. This protonation can be most effectively performed using 6 mol% ofBINAP and 10 mol% of... 

Table 18.3 Enantioselective protonation of trimethylsilyl enolates (71) with methanol catalyzed by (R)-BINAP- AgF complex.

The BINAP/AgF system catalyzes the reaction of allyltrimethoxy-silanes (Table 13). H NMR studies suggest a fast transmetallation and equilibration to the -crotylsilver species, followed presumably by a six-membered, chair-like transition state. The reaction is limited to aromatic aldehydes. ... 

Yanagisawa A, Kageyama H, Nakatsuka Y, Asakawa K, Matsumoto Y, Yamamoto H. Enantioselective addition of allylic trimethoxysilanes to aldehydes catalyzed by p-Tol-BINAP - AgF. Angew. Chem. Int. Ed. 1999 38 3701-3703. 

Yanagisawa A, Touge T, Arai T. Enantioselective protonation of silyl enolates catalyzed by a binap-AgF complex. Angew. Chem. Lnt. Ed. 2005 44 1546-1548. 

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