Mesityl bromide

The electrochemical analysis allowed the determination of kinetic constants for this reaction46. Thus, in the presence of bromobenzene, the rate constant for the oxidative addition was found to be equal to about 70 M 1 s 1. The a-arylnickel complexes are unstable, except those obtained from o-tolyl or mesityl bromide as starting substrates. In these particular cases, the arylnickel complexes can be prepared by electrolysis from an ArBr/NiBr2(bpy) equimolar ratio. However, the exhaustive electrolysis of an aromatic iodide in the presence of ZnBr2, in DMF and at —1.4 V/SCE, leads to the corresponding arylzinc compound but the yield remains low (<20%). Indeed, the aryl iodide is mainly converted to ArH according to, very likely, a radical process (Scheme 11). 

In 1997, Weidenbruch et al. successfully synthesized the first silicon analog of butadiene, hexaaryltetrasila-1,3-diene 64.17 Treatment of disilene 2 with lithium in DME at rt followed by the addition of 0.5 equivalent of mesityl bromide at —30 °C gives 64 as reddish brown crystals [Eq. (29)]. In a proposed mechanism, a half of the lithiodisilene 68, which is formed by the reductive Si-Ar bond cleavage [Eq. (8)], is... 

The first and as yet only molecule with conjugated Si=Si double bonds is the tetrasilabuta-1,3-diene (tetrasila-1,3-diene) 139, which was prepared as follows. The disilene 13 is treated with excess lithium to give the putative disilenyllithium species 137. In the second step of the sequence mesityl bromide was added in the expectation that the bulk of the aryl group and the poor solubility of mesityllithium would favor halogenation over the competing transarylation. Indeed, the bromodisilene 138 does appear to be formed smoothly but, like 137, it has not yet been positively identified. Intermolecular cleavage of lithium bromide from the two intermediates then furnishes the tetrasilabuta-1,3-diene 139 in 60% yield (equation 32)130. 

It is not strictly necessary to introduce the 1,1 -binaphthyl backbone. For axial chirality, the biphenyl scaffold is sufficient, provided that rotation around the phenyl-phenyl axis is sufficiently hindered. Hoveyda combined this reduced axial chiral motif with additional central chirality in the imidazole backbone (O and C ) [6,7], Synthetically, the task is accomplished by Buchwald-Hartwig amination of enantiomerically pure (H ,21 )-diphenylethylenediamine with 1-methoxy-I -iodo-biphenyl and subsequent reaction with mesityl bromide to introduce the bulky wingtip group on the second amino group of the chiral starting material. Ring closure reaction with triethyl orthoformate and hydrolysis of... 

Another approach utilized the reaction of tosyl azide with aryl Grignard reagents and fragmentation of the resulting tosyltriazene salts by aquv ous sodium pyrophosphate. Mesityl azide (124) was thus obtained from mesityl bromide in 63% yield... 

Shortening the reaetion time to sueh an extent that most of the digermene had reaeted before the formation of 27 eould heeome the main reaetion did indeed lead to eompound 28, whieh, hy subsequent reaetion with mesityl bromide, presumably resulted in the bromine derivative 29, from whieh the tetragermabutadiene 30 was formed by intermoleeular eoupling with elimination of LiBr. 

Mesitylmagnesium bromide prepared from mesityl bromide in dry ether added dropwise to an ice-cooled ethereal soln. of tosyl azide, stirring continued 0.5 hr., the resulting dry crude triazene salt suspended in dry ether, ice-cooled, aq. Na-pyrophosphate added dropwise at 0-20° to sequester the magnesium, and stirred overnight -> mesityl azide. Y ... 

BromomeBitylehe (2-Bromo. 1 3 S-trimethyl-benzene, mesityl bromide)... 

Mercuri-mesityl bromide (Mereuri-2 4 6> trimethylphenyl bromide)... 

The group of Lai and Rafii prepared a chiral imidazolium tetrafluoroborate from commercially available (lR,2R)-l,2-diamlnocyclohexane (Scheme 2.167) [61]. Palladium-catalyzed coupling of the diamine and mesityl bromide with 3 equiv of NaOtBu produced a diamine in the first step. Cyclization of this material with triethyl orthoformate in the presence of ammonium tetrafluoroborate led to the chiral BF, salt in an almost quantitative yield [62]. Finally, the chiral rhodium complex was synthesized by reacting the ligand precursor with an equimolar amount of potassium hexamethyldisilazide, followed by coordination to rhodium with [RhCl(COD)]2. 

The protected aminoalcohols 65 are prepared from N-Boc-(o-alkyl)anilines 64 by benzyUc metalation with tBuLi and addition to aldehydes. N-Deprotection with TFA leads to the free aminoalcohols 66, which are oxidized by mesityl bromide in the presence of Pd(PPh3)4 and K2CO3 the resulting (o-aminophenyl)ketones 67 cyclize in situ to the indoles (68). 

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