Calcium-BINOL complex

Molybdenum catalysts, Ruthenium porphyrins, Ruthenium(lll) complexes, Iron catalysts, Titanium catalysts. Sharpless epoxidation, Tungsten catalysts, Methyltrioxorhenium, Cobalt, Nickel, Platinum, Aerobic epoxidation, Lanthanum, Ytterbium, Calcium, BINOL-complexes. 2008 Elsevier B.v. 

In another approach, epoxidation of chalcone and substituted chalcones by TBHP was catalyzed by a calcium-BINOL complex bearing a poly(ethylene glycol) chain in 6-position [97]. Chalcone oxide yields between 92 and 95% were obtained with ee values ranging from 40 fo 47% using a catalyst loading of 10 mol%. The pol)Tneric catalyst is soluble in the reaction mixtures and can be precipitated and recovered. Reuse in three consecutive reactions showed a continuous decrease in activity and enantioselectivity. 

Shibasaki et al. also developed a barium complex (BaB-M, 14, Scheme 5) for the aldol reaction of acetophenone (la), making use of the strongly basic characteristic of barium alkoxide. The catalyst was prepared from Ba(0-z-Pr)2 and BINOL monomethyl ether, and the products were obtained in excellent yield with up to 70% ee (Scheme 6) [8], Shibasaki et al. attempted to incorporate a strong Bronsted base into the catalyst and developed a lanthanide heterobime-tallic catalyst (15) possessing lithium alkoxide moieties, which promoted the aldol reaction with up to 74% ee (Scheme 6) [9]. Noyori and Shibasaki et al. reported a calcium alkoxide catalyst (16) that was prepared from Ca[N(SiMe3)2]2,... 

Ikegami et al. reported an asymmetric Morita—Baylis—HUlman reaction using a BlNOL-calcium complex as a chiral Lewis acid and tributylphosphine as an achiral Lewis base (Scheme 2) [24]. It was found that an active calcium aryloxide catalyst could be prepared from Ca(0 Pr)2 and (f )-BINOL in THF. The reaction of cyclopentenone with 3-phenylpropionaldehyde was tested in the presence of the calcium complex, and the desired Morita-Bayhs-Hillman adduct was obtained in 62 % yield with 56 % ee. 

Kumaraswamy et al. reported asymmetric 1,4-addition reactions using chiral calcium complexes prepared from calcium chloride and dipotassium salt of BINOL or Hg-BESfOL (5,5, 6,6, 7,7, 8,8 -octahydro-l,l -bi-2-naphthol) [42-45]. After optimization of the calcium salts and reaction conditions, the calcium catalyst was successfully applied to asymmetric 1,4-additions of malonates or p-ketoesters to a,p-unsaturated carbonyl compounds (Tables 4 and 5) [42, 44]. Among the a,p-unsaturated carbonyl compounds employed in the reactions with malonates, cyclopentenone was found to be a suitable substrate, and high enantioselectivities were obtained (Table 4, entries 3 and 4). In the cases of p-ketoesters, 2-oxocyclopentanecarboxylates are suitable for this reaction, and good yields and good enantioselectivities were observed (Table 5, entries 2, 7, and 8). 

Table 5 Catalytic 1,4-addition reactions of p-ketoesters using a BINOL-calcium complex...

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