Aryl methane acidity

An aryl methane- or toluenesulfonate ester is stable to reduction with lithium aluminum hydride, to the acidic conditions used for nitration of an aromatic ring (HN03/H0Ac), and to the high temperatures (200-250°) of an Ullmann reaction. Aryl sulfonate esters, formed by reaction of a phenol with a sulfonyl chloride in pyridine or aqueous sodium hydroxide, are cleaved by warming in aqueous sodium hydroxide. ... 

The reactivity of the closely related system TpMe2PtMeH2 toward electrophiles in arene solvents has also been reported recently (68). The boron-based Lewis acid B(C6F5)3 induced elimination of methane and formation of an aryl(dihydrido) platinum(IV) complex via arene C-H activation (Scheme 17, A -> C). The active acid may be either B(C6F5)3 or alternatively a proton generated from B(C6F5)3 and trace water. It was proposed that the acid coordinates to a pyrazole nitrogen (shown in Scheme 17, B) forming an intermediate five-coordinate platinum(IV) complex, which readily eliminates methane. 

Sulphuric acid (concentrated). Widely used in desiccators. Suitable for drying bromine, saturated hydrocarbons, alkyl and aryl halides. Also suitable for drying the following gases hydrogen, nitrogen, carbon dioxide, carbon monoxide, chlorine, methane and paraffins. Unsuitable for alcohols, bases, ketones or phenols. Also available with an indicator (a cobalt salt, blue when dry and pink when wet) under the name Sicacide (from Merck) for desiccators. 

Alkyl and aryl sulfonates, e.g., methane or heptane sulfonic acid, camphorsulfonic acid For strong and weak bases, benzalkonium salts, catecholamines... 

Brunner and Fiirst[431 reported the synthesis of a series of optically active, extended chelate phosphines, one of which was derived from the reaction of 5-bromo-l,3-di(bor-neoxymethyl)benzene (69) and bis(dichlorophosphino)methane (70). Technically, the product (-)-l,l-bis 3, 5 -di(borneoxymethyl)phenyl]phosphino methane (71) is both a first tier P- and 1,3-aryl-branched dendrimer. Excluding distortions, the maximum distance between the P atom and the most distant H atom(s) is 11.9 A for the two-layer ligand 71. The Rh-catalyzed [Rh(cod)Cl]2) hydrogenation of (a)-/V-acetamidocinnamic acid in the presence of 71 afforded a disappointingly low [5.2 % ee (/ )] optical induction. 

Acetic, succinic and malonic acids (Table 1) are reported (4) to derive from Ar-CHa, Ar(CH2)2Ar (including hydroaromatic) and Ar-CH2 Ar (Ar - aromatic ring) units respectively. Examination of the concentrations of these major aliphatic products suggests that the medium lithotypes contain the highest concentrations of aryl methyl and Ar(CH2)2Ar structures. Diaryl methane units are proposed to be most significant in the pale lithotype possibly reflecting a resin input. 

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