Phenyl-transfer reaction

Dosa and Fu reported the first catalytic enantioselective phenyl transfer reaction to ketones (equation 25)100. In the presence of 1.5 equivalents of MeOH, the chiral tertiary alcohol was produced in good yield and with high enantioselectivity. Walsh and workers recently reported the Ti(OE -i Vchiral dihydroxybis(sulfonamide) catalyst 34 system, whereby enones have been converted to enantioenriched allyl alcohols101. 

A Lewis base ligand has been developed as the chiral catalyst. Dahmen, Brase and coworkers reported that the [2.2]paracyclophane-based chiral N,O-ligand 8 (2 mol%) affords (V-formylamine with 84-95% (equation 34)134. In this system, the phenyl transfer reaction also proceeds in a catalytic manner134b. 

Also [AuPh(TPA)] (TPA = l,3,5-triaza-7-phosphaadamantane) is obtained in a similar phenyl-transfer reaction using Na[BPh4] and [Au(TPA)3]C123 [Eq. (3)]. Although the [BPh4] anion is well known for participating in phenyl-transfer reactions with other transition metals,24 these appear to be the first reported examples of phenyl transfer to a gold center. 

These types of compounds are scarcely represented due to the low number of cationic ligands available and no general method for their synthesis exists. One example is [AuPh(MeTPA)]BPh4, which contains the cationic ligand MeTPA+, derived from 1,3,5-triaza-7-phosphaadamantane, synthesized through an unusual phenyl-transfer reaction in aqueous solution [Eq. (12)].23... 

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>. 

Treatment of (phosphine)gold(I) halides or tris(phosphinegold(I))oxonium salts with sodium tetraphenylborate affords arylgold(I) phosphine species through an unusual phenyl transfer reaction. Examples of this novel synthetic route are given in equations 22104 and 23105. 

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]. 

In 2005, Pizzuti and Superchi [72b] applied catalysts with a l,l -binaphthylazepine skeleton (Figure 7.9, D), but only a maximum of 54% ee was obtained in the phenyl transfer reaction from diphenylzinc to 4-chorobenzaldehyde. 

Scheme 7.46 An aminoalcohol ligand for the Zn-catalyzed enantioselective phenyl transfer reaction to aromatic aldehydes, as described by Pericas and coworkers [75].

The a-substituents on the tertiary alcohol also affect the reaction rate (Scheme 1.43). Whereas alcohols 1-3 were unreactive in the rhodium-catalyzed phenyl transfer reaction to enones, acridone-derived 5 reacted almost quantitatively under the otherwise same reaction conditions [60]. 

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... 

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