Fert-Butyl group

Recently, [2+3] cycloaddition reaction of 2-acetyl-[l,2,3]diazaphosphole (6) with 9-diazofluorenes (96) has been reported [105, 106], From the reaction in cyclohexane at rt, bicyclic phosphirane 97 was obtained as a result of the loss of nitrogen from the initial cycloadduct (Scheme 30). The cycloadduct, 3-spiro substituted 3H-[l,2,4]diazaphospholo-fused [l,2,3]diazaphosphole (98) could be isolated in good yield at room temperature in one case (R=/Bu) its stability was assigned to the presence of bulky fert-butyl group at 7-position. Use of polar solvent like dichloromethane led to the cyclic trimeric compound 99 (Scheme 30). 

Also as noted above any substituents present have little effect upon such oxidations. In 2,2 -methylenedifuran (118) the rings are attacked simultaneously giving a tetramethoxy derivative.297 Even the bulk of the fert-butyl group has little effect.298 The only marked substituent effect is that exerted by an aromatic (benzene, thiophene, furan) residue which, if directly attached at the 2-position, promotes elimination instead of the addition of another methoxy group. The net process then becomes one of arylation, as when 2-(2-thienyl)furan (119) is oxidized to 120.298 There are reports that acetyl and carboxy groups can be ejected during oxidation, but that ester groups are usually retained.287... 

Keeping in mind the recovery of the catalyst issue, Pozzi et al. [59] specifically tailored the salen ligand to suit its application in fluorous biphasic (FB) system (Figure 4). Accordingly, authors made modification at 5 and 5 position of Jacobsen catalyst by replacing fert-butyl group with perfluoroalkyl chain 6 or 3,5-bis heptadecafluorooctylphenyl 7, 8 [60]. 

The nitrolysis of tertiary amines in the form of fert-butylamines and methylenediamines has been used to synthesize numerous polynitramine-based energetic materials. In these reactions one of the N-C bonds is cleaved to generate a secondary nitramine and an alcohol the latter is usually 0-nitrated or oxidized under the reaction conditions (Equation 5.15). The ease in which nitrolysis occurs is related to the stability of the expelled alkyl cation. Consequently, the fert-butyl group and the iminium cation from methylenediamines are excellent leaving groups. 

Adolph and Cichra prepared a number of cyclic nitramines from the nitrolysis of tert-butyl protected Mannich products (Table 5.5). Nitrolysis of the fert-butyl groups was achieved with mixed acid, pure nitric acid or a mixture of nitric acid in acetic anhydride depending on the substrate. Pure nitric acid was found to affect the nitrolysis of both the ferr-butyl groups of (97), (Table 5.5, Entry 4) whereas the use of mixed acid led to the isolation of the product where only one of the ferf-butyl groups had undergone nitrolysis. Some of the cyclic nitramine products... 

Nitrolysis of a fert-butyl group is also a key step in the synthesis of the high performance explosive known as TNAZ (6). The nitrolysis of the A-fert-butylazetidine (103) has been achieved with acetic anhydride-nitric acid " and acetic anhydride-ammonium nitrate." ... 

Consider a proposed nucleophilic substitution reaction on the secondary alcohol shown using aqueous HBr. As a secondary alcohol, either Sn2 or SnI mechanisms are possible (see Section 6.2.3), but SnI is favoured because of the acidic environment and the large fert-butyl group hindering approach of the nucleophile. The expected SnI bromide product is formed, together with a smaller amount of the El-derived alkene in a competing reaction. 

Of the seven hydroxyl-containing peroxides listed in Table 2, six are tert-butylperoxy derivatives. Although the fert-butyl group kinetically stabilizes the peroxide so that its combustion enthalpy can be measured, its presence makes finding suitable reference compounds such as hydrocarbons and ethers to compare in reactions 2-9 more difficult. Reaction 6 is the only reaction for which there are enthalpy of formation data for the requisite comparison compounds. Three hydroxy peroxides, all from the same source, have remarkably consistent enthalpies of reaction 6 in both the liquid and gas phases. The mean values derived from the viciwaZ-dioxygen substimted alcohols, 2-tert-butylperoxyethanol, 2-fert-pentylperoxyethanol and 3-fert-butylperoxy-1,2-propanediol, are —304.0 + 4.1 kJmol (Iq) and —257.1 + 6.0 kJmol (g). However, these values... 

The most impressive anti selectivity is demonstrated in olefin 13, where only the trans methyl hydrogens react. This can be attributed to the fact that in TSi, apart from the 1,3 non-bonded interactions of the fert-butyl group with oxygen, in the newly forming double bond the methyl groups are cis to each other, which is unfavourable. 

By using a bulky substiment like the fert-butyl group, which always maintains an equatorial position. 

The iminium salt I3a, bearing a bulky fert-butyl group at nitrogen and a 2,4,6-tri-fert-butylphenyl group at carbon was deprotonated with potassium hydride at... 

The fert-butyl group is known as one of the most effective kinetic protectors and many reactive molecules have been stabilized and even isolated by using this group. For example, the divalent center of silylenes and germylenes, the heavy atom analogues of carbenes, have been shown to be blocked by tcrt-butyl groups. 

Azetes, which are stabilized by fert-butyl groups, react with trifluoroaceto-nitrile to give pyrimidines [233] (equation 51)... 

To have the antarafacial coplanar mechanism operate with the trans isomer, the transition state would have to have the fert-butyl group in the highly unfavorable axial position. 

A fert-butyl group is much larger than a methyl group and has a greater preference for the equatorial position. The most stable conformation of I -/ert-butyl-1 -mcthylcyclohexane has an axial methyl group and an equatorial tert-butyl group. 

Van der Waals strain between the fert-butyl groups in 2,2,4,4-tetramethylpentane causes the C-2—C-3—C-4 angle to open to 125-128°. 

In practice, zinc chloride was used as the Lewis acid to catalyze the Friedel-Crafts reaction (64% yield). Oxidation of the methyl groups occurs preferentially because the fert-butyl group has no benzylic hydrogens. 

Phenol itself can be arylated multiply around the oxygen up to five times by use of excess bromobenzene (Eq. 4) [8]. The use of a less polar solvent such as o-xylene is important no reaction of phenol occurs in DMF. The lack of hexa-arylated product may be attributed to steric reasons. When the 2- and 6-positions of phenol are masked by fert-butyl groups, the 4-position is arylated (Eq. (5) and path b in Scheme 3) [10]. It is worth noting that a diaryl ether is formed by reductive elimination of the alkoxyarylpalladium intermediate when a bulky phosphine ligand is used (path d) [11]. 

The tetrahedron is another of Plato s perfect solids. The hydrocarbon having this shape is known as tetrahedrane. Because of its three-membered rings, it has considerably more strain than cubane and has, so far, resisted many attempts to prepare it. However, tetrahedrane substituted with fert-butyl groups at its vertices was prepared in 1981. It is a stable solid at room temperature. 

The fert-butyl group (t-butyl or f-Bu) group has three methyl groups joined to the same carbon atom. Two t-Bu groups are found in BHT ( butylated hydroxy toluene ), an antioxidant added to some processed foods. 

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