Bromotoluene, oxidation

Bromobenzaldehyde has been prepared by the oxidation of -bromotoluene with chromyl chloride/ by saponification of the acetal from />-bromophenylmagnesium bromide and orthoformic ester/ by the oxidation of ethyl -bromobenzyl ether with nitric acid/ by the oxidation of /j-bromobenzyl bromide with lead nitrate/ and by the hydrolysis of i-bromobenzal bromide in the presence of calcium carbonate. ... 

Addition of ether to a nitration mixture (2-bromotoluene and cone, nitric acid) diluted with an equal volume of water in a separating funnel led to a low order explosion. This was attributed to oxidation of the ether (possibly containing alcohol) by the... 

It has been shown e that two mechanisms, elimination-addition (benzyne) and SN2 displacement, are operative in the liquid-phase hydrolysis of halogenatcd aromatic compounds. The formation of isomeric phenols as a result of the availability of the benzyne route makes the reaction of limited synthetic value. The incorporation of the copper-cuprous oxide system suppresses reaction via the benzyne route, so that the present method has general utility for the preparation of isomer-free phenols. For example, >-cresol is the only cresol formed from -bromotoluene under the conditions of this preparation. 

The relay compound 1025 required for the synthesis of all of these 7-oxygenated carbazole alkaloids was obtained starting from commercially available 4-bromo-toluene (1023) and m-anisidine (840) in two steps and 72% overall yield. Buchwald-Hartwig amination of 4-bromotoluene (1023) with m-anisidine (840) furnished quantitatively the corresponding diarylamine 1024. Oxidative cyclization of 1024 using catalytic amounts of palladium(ll) acetate afforded 3-methyl-7-methoxycarbazole (1025). Oxidation of 1025 with DDQ led to clauszoline-K (98), which, on cleavage of the methyl ether using boron tribromide, afforded 3-formyl-7-hydroxycarbazole (99) (546) (Scheme 5.149). 

Nitration of p-BrC HjCH, would have given about a 50-50 mixture of two products 2-nitro-4-bromotoluene would be unwanted. When oxidation precedes nitration, an excellent yield of the desired product is obtained. 

Adams platinum oxide catalyst is readily prepared from chloroplatinio acid or from ammonium chloroplatinate, and is employed for catalytio hydrogenation at pressures of one atmosphere to several atmospheres and from room temperature to about 90°. Reduction is usually carried out with rectified spirit or absolute alcohol as solvents. In some cases (e.g., the reduction of benzene, toluene, xylene, mesitylene, cymene and diphenyl ), the addition to the absolute alcohol solution of 2-5 per cent, of the volume of rectified spirit which has been saturated with hydrogen chloride increases the effectiveness of the catalyst under these conditions chlorobenzene, bromobenzene, o-, m- and p-bromotoluenes, p-dichloro- and p-dibromo-benzene are reduced completely but the halogens are simultaneously eliminated. Other solvents which are occasionally employed include glacial acetic acid, ethyl acetate, ethyl acetate with 17 per cent, acetic acid or 8 per cent, of alcohol. In the actual hydrogenation the platinum oxide Pt02,H20 is first reduced to an active form of finely-divided platinum, which is the real catalyst allowance must be made for the consumption of hydrogen in the process. 

SAMPLE SOLUTION (a) Reaction with ethylene oxide results in the addition of a —CH2CH2OH unit to the Grignard reagent. The Grignard reagent derived from o-bromotoluene (or o-chlorotoluene or o-iodotoluene) is appropriate here. 

Examples of the one-pot method are given in Table 1 [13]. The coupling works not only with aryl bromides that are electronically non-activated with regard to oxidative addition, for example bromobenzene and 3-bromotoluene, but also for the deactivated substrate 4-bromoanisole. When 3-bromotoluene is used as the substrate, in principle, two isomers can form. This indeed occurs and both the 2- and... 

Buchwald-Hartwig amination of p-bromotoluene with m-anisidine affords quantitatively the corresponding diarylamine. While oxidative cyclization using stoichiometric amounts of palladium(II) acetate provides only 36 % yield of 7-methoxy-3-methylcarbazole, up to 72 % yield is obtained using catalytic amounts of palladium(II). The highest turnover for the catalytic cycle is obtained with... 

Problem 18.4 What carboxylic acid can be prepared from p-bromotoluene (a) by direct oxidation (b) by free-radical chlorination followed by the nitrile synthesis ... 

Ask yourself, What is an immediate precursor of p-bromobenzoic acii There are two substituents on the ring, a carboxyl group (COOH), which i> meta-directing, and a bromine, which is ortho- emd para-directing. We ca brominate benzoic add, because the wrong isomer (m-bromobenzoic aci.. would be produced. We know, however, that oxidation of an alkylbenzcne yields a benzoic add. Thus, an immediate precursor of our target molecule m ht be p-bromotoluene. 

Derivation From p-bromotoluene by oxidation. Use Organic synthesis, detection of strontium. 

Information on conventional aromatic bromination and fluorination is at best incomplete, since the reported conditions usually do not give the electrode potential. Benzene was brominated to bromobenzene on graphite with Fe and KI salts as catalysts in solution (344). Toluene gave a mixture of o- and p-bromotoluene (344) however, the selectivity of the reaction is unknown. Similarly, phenol was oxidized to o- and p-bromophenol in HBr (345). 

Our approach to the 7-oxygenated carbazoles starts with a Buchwald-Hartwig amination of /M-anisidine (113) and p-bromotoluene (114) to give the diarylamine 115 in quantitative yield (Scheme 28) [148], For the oxidative cyclization of 115 we investigated different conditions (Table 1). The best yield was obtained using... 

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