1-Adamantyl trifluoroacetate

Manganese(III) acetate is poorly reactive with saturated hydrocarbons.514 However, oxidation of adamantane by Mn(OAc)3 in trifluoroacetic acid gives relatively high yields of 1-adamantyl trifluoroacetate, showing a preferential attack at tertiary C—H bonds.515 Oxidation of n-alkanes by air in the presence of manganese catalysts constitutes the basis for an industrial process for the manufacture of synthetic fatty acids from n-alkanes of petroleum origin, which has been commercially developed in the Soviet Union.516... 

Many carbamates have been used as protective groups. They are arranged in this chapter in order of increasing complexity of stmcture. The most useful compounds do not necessarily have the simplest stmctures, but are /-butyl (BOC), readily cleaved by acidic hydrolysis benzyl (Cbz or Z), cleaved by catalytic hy-drogenolysis 2,4-dichlorobenzyl, stable to the acid-catalyzed hydrolysis of benzyl and /-butyl carbamates 2-(biphenylyl)isopropyl, cleaved more easily than /-butyl carbamate by dilute acetic acid 9-fluorenylmethyl, cleaved by /3-elimination with base isonicotinyl, cleaved by reduction with zinc in acetic acid 1-adamantyl, readily cleaved by trifluoroacetic acid and ally], readily cleaved by Pd-catalyzed isomerisation. 

To a mixture of adamantyl bromide (0.5 mmol) and trifluoroacetate salt of lepidine (2.5 mmol) in benzene (6 ml) were added (trimethylsilyl)silane (1.0 mmol) and AIBN (1.0 mmol). The mixture was heated at 80 °C for 14 h under an argon atmosphere. After the reaction, the reaction mixture was washed with sat. aq. NaHC03. The organic layer was dried over Na2S04. After removal of the solvent, the residue was chromatographed on silica gel to give 2-(l-adamantyl)-4-methylquinoline in 90% (125 mg) yield [33]. 

The above refinements of the interpretation of earlier work have been brought about by two important developments, recognition from studies in trifluoroacetic acid that acetic and formic acids are nucleophilic (Peterson et al., 1965) and the use of 2-adamantyl tosylate as a reference point for SnI reactivity (Schleyer et al., 1970). These developments have led to sensitive ways of detecting nucleophilic assistance and have shown that solvolyses of secondary substrates in acetic and formic acids may be significantly nucleophilically assisted (Table 2). Previous arguments were based on less sensitive tests such as the rate-accelerating effect of low concentrations of added nucleophiles, which must be appropriately oriented and desolvated before they are able nucleophilically to assist in the displacement reaction (Peterson et al., 1967). 

Simple alkanes can be converted to esters with dialkyloxrranes. Cyclic alkanes are oxidized to alcohols with dimethyl dioxirane. " Cyclohexane was converted to cyclohexyl trifluoroacetate with di(trifluoromethyl) dioxrrane and trifluoroacetic anhydride and also with RuCl3/MeC03H/CF3C02H. Dimethyl dioxrrane converts alkanes to alcohols in some cases. Adamantane is converted to adamantyl alcohol with DDQ (p. 1710) and triilic acid. The mechanism of oxygen insertion into alkanes has been examined. ... 

Solvent Dependence of Reactivity. Solvolysis reactions were investigated to obtain structure-reactivity relationships, but these studies were complicated by the solvent dependence of relative rates (Table I). These results show a 1010 variation in relative rates of solvolyses of methyl and 2-adamantyl tosylates (2-AdOTs) in trifluoroacetic acid (TFA) compared with those of ethanolysis. Even for two secondary systems, relative rates for 2-AdOTs-(CH3)2CHOTs vary from 36 in trifluoroacetic acid to 0.0011 in ethanol (4). Hence, separate intrinsic structural effects must be separated from solvent-induced effects. 

Manganese(III) acetate is poorly reactive with saturated hydrocarbons. However, oxidation of adamantane by Mn(OAc)3 in trifluoroacetic acid gives relatively high yields of 1-adamantyl... 

This dichotomy is quite evident in the reaction of cydooctane with nitronium trifluoroacetate. The products obtained were cyclooctyl triflu-oroacetate, cyclooctyl nitrate and nitrocydooctane. Conversion of adaman-tane to 1-fluoroadamantane in 95% 3ueld on reaction with nitronium tetrafluoroborate in pyridine polyhydrogen fluoride indicates that formation of adamantyl cation by formal hydride abstraction is a significant alternative to the nitration-protodenitration pathway. 

TFA is 99 vol. % trifluoroacetic acid, 1 vol. % water. The sulfonate esters used were in 90E the p-bromobenzenesulfonate in 50E and 97TFE isopropyl-p-bromobenzenesulfonate and 2,2,2-trifluoroethanesulfonate, pinacolyl p-bromobenzenesulfonate and 2-adamantyl 2,2,2-trifluoroethanesuifonate in 99TFA, isopropyl and p-bromobenzenesulfonate, pinacolyl p-toluenesulfonate and 2-adamantyl p-toluenesulfonate and p-bromobenzenesulfonate. 

The comparison of the oxidation of a series of substituted adamantanes (t-butyl, methyl, adamantyl) by lead(IV), cobalt(III) and manganese(III) trifluoroacetates with the corresponding anodic oxidations in acetonitrile or trifluoroacetic acid shows that the electrochemical oxidation proceeds via a radical cation intermediate, whilst the metal salts form products by CH abstraction". The preparative result is that, in anodic oxidation, preferentially products of fragmentation of the intermediate radical cation are found, whilst with the metal salts hydrogen substitution is being obtained preferentially. 

An alternative to the BOC group for protection of an amino-group is the l-(l-adamantyl)-l-methylethoxycarbonyl (Adpoc) moiety (200). It is stable to hydrogenolysis and is removed about one thousand times faster than A -BOC groups on treatment with 3% aqueous trifluoroacetic acid. "... 

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