Toluene adamantylation

The -butyl ester is a relatively hindered ester, and many of the following methods for its formation should be, and in many cases are, equally effective for the preparation of other hindered esters. The related 1- and 2-adamantyl esters have been used for the protection of aspartic acid and other amino acids (1-AdOH, toluene, dimethyl sulfate, cat. TsOH, 70-80% yield). ... 

Alkylidene-phosphapyrazolines 98-101 are much more thermally stable than their relatives 88, which do not possess the exo-methylene substitution. Dediazo-niation of 98 required heating in toluene at 110°C and gave one or more of the following products, probably via intermediate diphenylmethylene(vinylidene)phos-phoranes methylenephosphiranes, (2-siloxyvinyl)phosphanes, 2//-l,3-oxaphos-pholes, and l-alkylidene-2,3-dihydro-l//-benzo[c]phospholes (169). Thermolysis of 100 ( R = t-Bu, 1-adamantyl) afforded isolable 2-phosphabutadienes (169). The photochemical elimination of N2 from 98 generated cyclic azomethine imine dipoles 104 (Scheme 8.24), which rearrange to compounds 105 and 106 that could be further trapped with DMAD to form 107 (170). 

In adamantylation of toluene a close to 2 1 meta- and para-substituted isomer distribution was observed. 

Boron tris(triflate) has also been tested in the adamantylation of benzene and toluene with 1-haloadamantanes [Eq. (5.87)] and2-haloadamantanes.232B(OTf)3 is a highly active catalyst to promote the transformation in very short time under mild conditions to yield isomeric aryladamantanes and adamantane byproduct (Table 5.15). Of the isomeric 1-tolyladamantanes, 1-meto-tolyladamantane predominates, whereas the para isomer is the main product of the 2-tolyladamantanes. The ortho isomers were... 

Table 5.15. Adamantylation of Toluene with 1-Haloadamantanes in the Presence of B(OTf)3232...

Laali et al.234 have developed a method to the highly selective pura-adamantylation of arenes (toluene, ethylbenzene, anisole) with haloadamantanes (1-chloro- and 1-bromoadamantane, l-bromo-3,5,7-trimethyladamantane) and 1-adamantanol promoted by triflic acid in butylmethylimidazolium triflate [BMIM][OTf] ionic liquid. In contrast to reactions mn in 1,2-dichloroethane, little or no adamantane byproduct was detected in [BMIM][OTf. Furthermore, no isomerization of para-tolyladamantane was observed supporting the intramolecular nature of the formation of meta isomers. In competitive experiments with benzene-toluene mixture (1 1 molar ratio), high substrate selectivities were found (kT/kB = 16-17) irrespective of the alkylating agent. This is in sharp contrast to values about unity measured in 1,2-dichloroethane. 

In a similar study, Nafion-H beads, 10% Nafion-H on silica, and 13% Nafion-silica were compared in the adamantylation of toluene with 1-bromoadamantane.239 13% Nafion-silica nanocomposite exhibited the highest activity and showed achangeinthe isomeric ratio of the two alkylated products the para/me ta ratio shifted to lower values in prolonged reaction (Table 5.20). Acidity is known to exert a significant influence on... 

Table 5.19. Adamantylation of Bromobenzene and Toluene over Various Solid Acids238...

Table 5.20. Adamantylation of Toluene over Various Nafion Catalysts239...

The 1-adamantyl (1-Ada) esters exhibit increased acid stability if compared to the tert-butyl esters.These amino acid esters are prepared by reaction of the amino acid tosylates with adamantan-l-ol and dimethyl sulfite in boiling toluene. Removal of the adamantyl ester is effected by neat TFA within 1 hour or TFAyCH2Cl2 (1-2) within 15 hours. N-Terminal Boc groups are selectively cleaved with 4 M HCl in anhydrous dioxane (rt, 25 noin) in the presence of the 1-adamantyl ester. 

Further support of this mechanism has been advanced by a kinetic study of the decomposition of 1-adamantyl chloroformate . The activation parameters, however, for the decomposition of this chloroformate in benzene (A/f = 21.61 0.17 kcal.mole , AS = —12.03 + 0.59 eu) do not differ significantly from those for a-phenethyl chloroformate in toluene (Table 11). 

Alkyldenitration by the 1-adamantyl radical in / ara-substituted nitrobenzenes (/7-X-C6H4-NO2) is an efficient process only for electron-poor arenes. Thus, while for anisole (X = OMe), benzene (X = H) and toluene (X = Me) derivatives no ipso products were observed, the analogous reaction with nitrobenzenes bearing electron withdrawing substituents (X = NO2, CN, SO2R, CO2R, COMe, CHO) afforded the corresponding alkyldenitration products in 45-60 /) yield [30]. The effect of the... 

Another example involves the preparation of novel polymers containing W calix-arenes. Such materials, formed by the electropolymerization of species 7.51 (Scheme 7.10), show high conductivity values of up to 15.5 Scm . It was possible to use the resultant polymers to specifically recognize p-xylene. For example, formation of the polymers with R=adamantyl in the presence of p-xylene led to films with a 10-fold increase in conductivity over those formed in the absence of xylene or in the presence of toluene [92]. 

Bi (l-adamantyl)imidazolium tetrafluoroborate (lAd.BF4) [286014-42-4] M 424.3, m 277-282". This NHC (N-Heterocychc Carbene) precursor is prepared by estabhshed procedtrres from 2 mols of amine, 1 mol of glyoxal and 1 mol of formaldehyde in toluene/H20 in the presence of HBF4. It is as effective, if not better in some cases, in many of the metal mediated catalytic reactiorrs as other NHCs. For further detail see the entry on IPr.Cl [250285-32-6]. [Arduengo USPatent 5 077 414 1991, Chem Abstr 116 106289 1002, Kantchev, O Brien Orgm Aldrichimica Acta 39 97 2006, Phillips, Chan Schsidi Aldrichimica Acta 42 55 2009]. 

Selective oxidations of benzylic and aliphatic alcohols to aldehydes and esters, by O2 in the presence of the ligand Q, o -bis(di-f-butyl phosphino)-o-xylene or Bu"P(l-adamantyl)2 and the additive AgPFg in toluene and in the presence of various alcohols, were achieved using Pd(OAc)2 as the catalyst without the need for additional organic hydrogen acceptors. " In a parallel study, the [PdCl2(MeCN)2]-catalysed esterification of benzylic alcohols with methanol and various long-chain aliphatic alcohols in the... 

There is very good evidence that if the cyclopropyl group of a cyclo-propylcarbinyl derivative can interact with the developing cationic center in a bisected conformation a very large rate enhancement results, whereas if this conformation is prevented sterically, there is no rate enhancement. Thus on the basis of the rate of solvolysis of 8,9-dehydro-2-adamantyl 3,5-dinitrobenzoate in aqueous acetone it was estimated that the corresponding toluene-p-sulfonate (43) would undergo acetolysis about 8 powers of 10 faster than 2-adamantyl toluene-p-sulfonate (44). It was also esti-... 

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