1-Bromoadamantane, adamantylation with

Reactions of Mg/ with adamantyl halides are among the most unusual to be considered in the recent literature. I-Bromoadamantane (adamantyl bromide, AdBrl has received the most attention [651. 

Vinyl cations also have been invoked as intermediates in the addition of carbonium ions generated in strong acid to acetylene (50-53). Sasaki et al (50) observed 1-adamantyl methyl ketone, 25, as the sole product in the reaction of acetylene with 1-bromoadamantane in concentrated H2SO4 at 5°. Bott (51), on the other hand, reported a mixture consisting of 75% 1-adamantylacetaldehyde,... 

Treatment of pyrazole with 1-bromoadamantane affords either 4-(l-adamantyl)pyrazole (94TL183, 94H(37)1623) or 3(5)-(l-adamantyl)pyrazole (94CL2079) depending on the conditions (heating in a sealed tube or heating in a microwave oven). (Other cases of C-alkylation of azoles are in Section 3.4.1.3.10). 

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... 

Previously, it has been noted that the solvolysis rates of both 3-methyl-l-bromoadamantane and 3,5-dimethyl-1-bromoadamantane are slower than 1-bromoadamantane itself. This result was felt to be inconsistent with any mechanism which distributed positive charge to all bridgehead positions of the adamantyl cation under solvolysis conditions since the introduction of tertiary resonance contributors (cf. Eq. (49)) should enhance rather than retard solvolysis rates 56,164 ... 

Treatment of 1-bromoadamantane with AlBr3 in the presence of ethylene at -75 °C to give l-(j3-bromoethyl)-adamantane 202) followed by reduction 20°) results in good yields of 1-ethyladamantane (Eq. (63)). Wolf-Kishner 164) or Clemensen 203) reduction of commercially available methyl adamantyl ketone provides an alternative route for the preparation of this compound. 

To a mixture of 1-bromoadamantane (0.3 mmol), TPDS (0.45 mmol), and caffeine salt (1.5 mmol) with camphorsulfonic acid was added AIBN (0.45 mmol) over 8 h (5 times in 2 h intervals). After 4 h, TPDS (0.45 mmol) was added again. After a total of 22 h, sat. aq. NaHC03 solution was added and the mixture was extracted with ethyl acetate. The organic layer was dried over Na2S04. After removal of the solvent, the residue was chromatographed on silica gel to provide 2-(l-adamantyl)caffeine in 55% yield [30]. 

ET-initiated alkylation of azines in the presence of alkyl halides has been found to occur under electrochemical conditions according to Scheme 43. Either alkylated dihydroheterocycles or the rearomatized products are obtained. As an example, electroreduction of quinoline in the presence of 1-bromoadamantane gives alkylated quinolines (10 % in position 2, 5 % in position 7) and 2-methyl- and 2-methoxyquinoline give the 7-adamantyl derivative in 20 and 23 % yield, respectively. 1,10-Phenanthroline gives bis(adamantyl) derivatives, whereas isoquinoline and phenanthridine give the 6-adamantyl-5,6-dihydro and the 9-adamantyl-9,10-dihydro derivatives, respectively [132]. Reaction with terr-butyl chloride also gives alkylated dihydroheterocycles [133]. Arylation has also been performed, e.g. in the synthesis of pyrazolophenanthridines (62, Scheme 44) [134]. 

Zhukov and coworkers alkylated naphthalene with 1-bromoadamantane in the presence of ZnCl2-H2O to afford 2-(l-adamantyl)naphthalene in 90% yield (equation 14). 

Phenols are highly reactive toward the Friedel-Crafts alkylation reactions involving tertiary alkyl halides. Phenol, 2-methylphenol and 2,6-dimethylphenol react with tertiary alkyl halides such as 1-bromoadamantane in the absence of any external catalyst to give exclusively the para-(l-adamantyl)phenols (equation 1). These compounds have found... 

Reductive Addition. Radical addition to activated olefins with alkyl bromides to form a carbon-carbon bond can be also carried out in the presence of TPDS initiated by AIBN in ethanol. Other activated olefins such as diethyl vinylphosphonate and ethyl acrylate can be also used in the addition reaction. The reductive addition of 1-bromoadamantane to diethyl vinylphosphonate with TPDS initiated by AIBN to form the corresponding diethyl 2(l-adamantyl)ethylphosphonate in good yield is shown in eq 4. 

The apocamphyl case is an extreme one, and bridgehead carbonium ions in other systems are more accessible. Inclusion of more atoms in the bridge gives a more flexible molecule and allows carbonium ion formation to proceed with a somewhat lower activation energy. Thus, the relative solvolysis rates of the bridgehead bromides 1-bromoadamantane, l-bromobicyclo[2.2.2]octane, and 1-bromobicyclo[2.2.1]heptane in 80% ethanol at 25°C are 1,10", and Under the same conditions, the rate of solvolysis of tert-butyl bromide is 1000 times that of 1-bromoadamantane. The 1-adamantyl cation is sufficiently stable to be generated in antimony pentafluoride in concentrations sufficient for observation by NMR. ... 

By aetion of 1-bromoadamantane on N-unsubstituted imidazole with ratio 1 2 at 190-200°C during 2 hours, N-(l-adamantyl)imidazole (20) with 74% yield was obtained [26],... 

In 1985, Gonzalez and co. [26] obtained N-(l-adamantyl)benzimidazole (86) by heating 1-bromoadamantane and benzimidazole (1 2) at 190°C with 69% yield. The antiviral activity of the compound was studied. 

In o-dichlorobenzene solution adainantylation of benzunidazole afforded 1-(l-adamantyl)benzimidazole ( 86) and l,3-di(l-adamantyl)-benzimidazolium bromide 134). They report here on reaction of benzimidazole with 1-bromoadamantane at 110-180°C and various reagents ratio [86. ... 

Among the known classes of heteroaromatic carbenes, the benzimidazole derivatives have received the least attention thus far. They [89] present new results in terms of the synthesis and properties of stable heteroaromatic monocarbenes and biscarbenes of the benzimidazole series. One of the major aims in this area was the attachment of sterically bulky groups to the benzimidazole nucleus. The introduction of the 1-adamantyl substituent into the benzimidazole system was achieved by direct adamantylation of benzimidazole using 1-bromoadamantane in the presence of sodium acetate in acetic acid. However, in this case the reaction was incomplete and yields of only 33% of pure salt 134 were realized. In o-dichlorobenzene in the presence of potassium carbonate, a 54% yield of l-(l-adamantyl)benzimidazole (86) can be achieved and this compound can be further quatemized by treatment with 1 -bromoadamantane in o-dichlorobenzene to afford a high yield of salt 134 (90%).As is well known, in the... 

Most of the substrates discussed before feature sp or sp -hybridized carbon atoms connected to the leaving groups. However, there are some reports indicating that some sp -hybridized substrates undergo Heck-type reactions. At least in some cases, radicals or cationic species are involved. For example, 1-bromoadamantane derivatives react with alkenes under palladium catalysis to give rise to 1-adamantyl alkenes (Scheme 5-39) (Experimental Procedure below). 

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