Haloalkanes, oxidation

Fox BG, Bomeman JG, Wackett LP, et al. 1990. Haloalkane oxidation by the soluble methane monooxygenase irom Methylosinus trichosporium OB3b Mechanistic and environmental implications. Biochemistry 29 6419-6427. 

Hall process (Hall-Herault process) The production of aluminum by the electrolysis of aluminum oxide dissolved in molten cryolite, haloalkane An alkane with a halogen substituent. 

For example, direct treatment of red phosphorus with potassium hydroxide in a mixture of dioxane and water with a phase-transfer catalyst (benzyltriethylammonium chloride) allows direct reaction with primary haloalkanes to form the trialkylphosphine oxide in moderate (60-65%) yield.1415 Allylic and benzylic halides are similarly reported to generate the corresponding tertiary phosphine oxides. When the reaction is performed with a,(o-dihalides, cyclic products are generated only with four- and five-carbon chains the third site... 

Although sodium sulphide reacts readily with haloalkanes [2] and activated aryl halides (see Chapter 2) [e.g. 3-5] in the presence of a quaternary ammonium catalyst to form symmetrical thioethers (Table 4.1), a major side reaction results in the formation of disulphides owing to the oxidation of the intermediate thiols under the basic conditions. Consequently, little use has been made of this procedure for the synthesis of thioethers [3, 6], but the corresponding reaction of the a,(0-dihaloalkanes to yield cyclic thioethers has proved to be a valuable procedure for the synthesis of thietanes [7] (Table 4.2). The ring closure with the secondary dihaloalkanes is considerably more difficult to effect than is the reaction of the primary dihaloalkanes. 1,3-Dihydrobenzo[c]thiophene (89%) is produced in the reaction of 1,2-bis(bromomethyl)benzene with sodium sulphide (Scheme 4.1) [8]. The direct... 

As indicated above, the traditional base-catalysed hydrolysis of 0,5-dialkyl thio-carbonates for the synthesis of thiols is generally unsatisfactory, as oxidation leads to the formation of disulphides. Under phase-transfer conditions, the procedure produces thioethers to the virtual exclusion of the thiols, as a result of the slow release of the thiolate anions in the presence of the electrophilic ester. However, a simple modification of the reaction conditions provides an efficient one-pot reaction [50] from haloalkanes (Table 4.15) via the intermediate formation of the thermally labile (9-/ert-butyl-5-alkyl dithiocarbonates (Scheme 4.8). 

As an alternative to the oxidation of sulphides and sulphoxides (see Chapter 10), sulphones can be prepared by the nucleophilic substitution reaction of the sulphinite anion on haloalkanes. In the absence of a phase-transfer catalyst, the reaction times are generally long and the yields are low, and undesirable O-alkylation of the sulphinite anion competes with S-alkylation. The stoichiometric reaction of the preformed tetra-n-butylammonium salt of 4-toluenesulphinic acid with haloalkanes produces 4-tolyl sulphones in high yield [1], but it has been demonstrated that equally good... 

Haloalkanes are readily oxidized to the corresponding aldehydes or ketones. The best yields are attained with secondary alcohols and unsaturated hydroxyl groups [5]. a-Nitroketones, which are valuable intermediates in organic synthesis, are... 

Catalysed oxidation of non-activated haloalkanes by hypochlorite provides an attractive low-cost and convenient procedure for their conversion into carbonyl compounds [6] primary haloalkanes produce carboxylic acids and secondary haloalkanes are converted into ketones (Table 10.12). Secondary amines are oxidized to ketones under analogous conditions, whereas primary amines yield nitriles (Table 10.13) [1,2], o-Nitroanilines are oxidized to benzofurazan-1-oxides [15]. 

The haloalkane (2.5 mmol) in MeCN (5 ml) is stirred with aqueous NaOCl (8%, 15 ml) and TBA-HS04 (85 mg, 0.25 mmol) at room temperature for 7-24 h until the halide has been consumed. H20 (35 ml) and Et20 (25 ml) are added and the organic phase is separated, washed with H20 (2x10 ml), dried (MgS04), and evaporated to yield the oxidation products. 

Selected examples of the oxidation of primary and secondary haloalkanes to carboxylic... 

Another reaction of dehalogenation, the oxidative dehalogenation of haloalkyl groups, summarized in Fig. 11.3,b (Chapt. 8 in [50]), has also been observed in mammals and other organisms. Here, the haloalkane is oxidized by a cytochrome P450 enzyme to form a hydroxylated intermediate that loses HX to become a carbonyl derivative. The latter is then reduced by dehydrogenases to the corresponding alcohol (Fig. 11.3,c), or, when the carbonyl derivative is an aldehyde, oxidation to the acid can occur (Fig. 11.3,c). 

A review of the oxidation of haloalkanes with halogens and their derivatives has appeared. ... 

OXIDATION OF ALKANES, HALOALKANES AND ALKENES tion of 24 is directed towards a five-membered ring because of the phenyl substitu-... 

Chapter 2 - Oxidation of Alkanes, Haloalkanes and Alkenes, Pages 27-53... 

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