Asymmetric phenyl transfer reactions

Various ferrocene-based organosilanols 165 have been synthesized in two steps fi om chiral 2-ferrocenyl oxazolines 163. Diastereoselective ortho-lithiation with sec-BuLi followed by electrophilic attack with chlorosilanes gave diastereomerically enriched 164, which were oxidized in air with [IrCl(C8Hi2)]2 as catalyst to give, after purification, stereochemically homogeneous samples of 165. Their application in asymmetric phenyl transfer reactions to substituted benzaldehydes afforded products with high ee (up to 91%) <050L1407>. 

Figure 7.9 (A) The planar-chiral -cyclopentadienylrhenium(l)tricarbonyl complex for the asymmetric phenyl transfer reaction...

B) amino alcohols used in asymmetric phenyl transfer reactions [71] (C) and (D) binaphthyl-based amino alcohols [72] and (e) BINOL-derived chiral ligand [73]. 

Further examples of papers are 4-ferrocenyl-l,3-oxazoline ligands in asymmetric allylation reactions ortho-silylation of 2,2, -bis(oxazolinyl)-l,l -bis(diphenylphosphino)ferrocenes in palladium-catalyzed asymmetric allylic alkylations polymer-supported ferrocenyl oxazalines for asymmetric phenyl-transfer reactions 1 -substituted... 

The asymmetric phase transfer reaction was extended by the Merck group to a substrate which lacked the phenyl group, Eq. (3) [17]. 

In middle of the 1980s, efficient asymmetric phase-transfer reactions using catalytic amounts of Al-benzylcinchoninium chlorides were developed by researchers at Merck. This catalyst was able to alkylate 2-substituted-2-phenyl indanones with high ee (up to 94% ee) [20]. 

Table 17) with two substituents in position C3 the oxygen transfer by the chiral hydroperoxides occurred from the same enantioface of the double bond, while epoxidation of the (ii)-phenyl-substituted substrates 142c,g,i resulted in the formation of the opposite epoxide enantiomer in excess. In 2000 Hamann and coworkers reported a new saturated protected carbohydrate hydroperoxide 69b , which showed high asymmetric induction in the vanadium-catalyzed epoxidation reaction of 3-methyl-2-buten-l-ol. The ee of 90% obtained was a milestone in the field of stereoselective oxygen transfer with optically active hydroperoxides. Unfortunately, the tertiary allylic alcohol 2-methyl-3-buten-2-ol was epoxidized with low enantioselectivity (ee 18%) with the same catalytic system . 

There are only a few reports on chiral phase transfer mediated alkylations". This approach, which seems to offer excellent opportunities for simple asymmetric procedures, has been demonstrated in the catalytic, enantioselective alkylation of racemic 6,7-dichloro-5-methoxy-2-phenyl-l-indanone (1) to form ( + )-indacrinone (4)100. /V-[4-(tnfluoromethyl)phenylmethyl]cinchoninium bromide (2) is one of the most effective catalysts for this reaction. The choice of reaction variables is very important and reaction conditions have been selected which afford very high asymmetric induction (92% cc). A transition state model 3 based on ion pairing between the indanone anion and the benzylcinchoninium cation has been proposed 10°. 

Transfer of a metal carbene moiety from a metal carbene complex to a heteroatom other than oxygen, sulfur, and nitrogen is possible. One such example is the report by Uemura and co-workers, who disclosed catalytic asymmetric reaction of ethyl diazoacetate with ( )-cinnamyl phenyl selenide 193 (Equation (30))." The reaction afforded 194 as a diastereomeric mixture (58 42). Using Rh2(5[Pg.173]

The efficient phase-transfer-catalyzed alkylation strategy with le was successfully applied by Jew and Park to the asymmetric synthesis of a-alkyl serines, using phenyl oxazoline derivative 53 as a requisite substrate [28]. The reaction is general, however, and provides a practical access to a variety of optically active a-alkyl serines through acidic hydrolysis of 54 (Scheme 5.26). 

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