Aryl oxide anions

Acyclic and cyclic ethers are synthesized by the reaction of activated alcohols with alkoxide or aryl oxide anions. Alkyl halides and epoxides can also be utilized as versatile electrophiles for the preparation... 

Recently, the groups of Mukaiyama [69] and Feng [70] independently demonstrated that aryl oxide anions such as phenoxide [69] or binaphthoxide [70] can be used instead of fluoride to activate (TMS)CF3 as a Lewis base. Several types of aromatic ketones and aldehydes were smoothly trifluoromethylated within a few hours in the presence of cinchona-based quaternary ammonium salts bearing an aryl oxide anion 148 or 149, affording the corresponding product in excellent yields and with moderate to high ee values (up to 87% ee) (Schemes 8.58 and 8.59). 

S.A. Ba-Saif et al.. Dependence of Transition State Structure on Nucleophile in the Reaction of Aryl Oxide Anions with Aryl Diphenylphosphate Esters, J. Chem. Soc., Perkin Trans. 2, 1991, 1653. 

Let us consider the reaction of aryl isothiocyanates with aryl oxide anions (Eqn. 25) [18] ... 

The reaction of aryl oxide anions with 2-aryloxazolinones (Eqn. 26) [19] is another example where the application of the effective charge concept is not appropriate. 

When the nickel complexes [NiX2(PPh3)2] (X = Cl, Br) are reduced electrochemically in the presence of C02 and aryl halides, aryl carboxylate anions are formed.585 The reduction leads to nickel(O) complexes which then undergo oxidative addition of the aryl halide followed by insertion of C02. Further reduction then gives the product and regenerates nickel(O) (Scheme 55). 

A number of Re aryl oxides exist in some of the same structural classes described for the Re alkyl oxides. Examples are the paramagnetic d ReOAr4 (Ar = mesityl, o-tolyl, o-methoxyphenyl), the anionic [ReO(mes)4] and [Re02(mes)2]. Paramagnetic Re02(Ar)2 (Ar = mesityl, xylyl) do not have alkyl counterparts becanse of their avoided dimerization, bnt Mo and Os analognes are known. 

An indirect method for the synthesis of aryl alkyl sulhdes involves treatment of an aryl halide with butyllithium and then elemental sulfur. The resulting thiophen-oxide anion reacts with an alkyl halide to give the targeted sulhde. °... 

Chiral ammonium betaines are a particular class of bifunctional BB-based catalysts that have been successfully applied in the aza-Henry reaction of N-Boc imines and a-substituted a-nitroesters [42]. The catalyst structure displays an intramolecular ion-pairing quaternary ammonium aryl-oxide and the mode of action may involve deprotonation of the pronucleophile by the basic anion to furnish and onium ion as its conjugate acid form. Catalyst loadings as low as lmol% produced the corresponding quaternary-tertiary aza-Henry adducts in excellent yields and enantioselectivities, albeit with low to moderate diastereoselectivities (Scheme 29.18). The lowest de s (up to 33%) were obtained with aliphatic N-Boc imines (R = CH2CH2Ph, -octyl). 

Eisch, Behrooz and Galle196 give compelling evidence for the intervention of radical species in the desulphonylation of certain acetylenic or aryl sulphones with metal alkyls having a lower oxidation potential at the anionic carbon. The primary evidence presented by these workers is that the reaction of 5-hexenylmagnesium chloride outlined in equation (85) gives a mixture of desulphonylation products, in accord with the known behaviour of the 5-hexenyl radical, in which the cyclopentylmethyl radical is also formed. 

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