Halogenation reductive

Adipic acid undergoes the usual reactions of carboxyflc acids, including esterification, amidation, reduction, halogenation, salt formation, and dehydration. Because of its biflmctional nature, it also undergoes several industrially significant polymerization reactions. 

The control of chemical reactions (e.g., esterification, sulfonation, nitration, alkylation, polymerization, oxidation, reduction, halogenation) and associated hazards are an essential aspect of chemical manufacture in the CPI. The industries manufacture nearly all their products, such as inorganic, organic, agricultural, polymers, and pharmaceuticals, through the control of reactive chemicals. The reactions that occur are generally without incident. Barton and Nolan [1] examined exothermic runaway incidents and found that the principal causes were ... 

Reductive halogenation can be achieved by reducing a higher halide with the parent metal, another metal or hydrogen ... 

Epoxides can be reductively halogenated (the product is the alkyl bromide or iodide rather than the alcohol) with Me3SiCI—NaX—(Mc2SiH)20 (1,1,3,3-tetra-methyldisiloxane). ... 

Although homonuclear cyclosilanes have been known for a long time, it is only recently that the smallest members of this series, the cyclotrisilanes, have become available [1], Cyclotrisilanes 1 are obtained by reductive halogen elimination from ort/zo-disubstituted diaryldichlorosilanes [2, 3] or, in particular cases, from hexaalkyl-l,3-dichlorotrisilanes [4]. 

The activity of PK and NRPSs is often precluded and/or followed by actions upon the natural products by modifying enzymes. There exists a first level of diversity in which the monomers for respective synthases must be created. For instance, in the case of many NRPs, noncanonical amino acids must be biosynthesized by a series of enzymes found within the biosynthetic gene cluster in order for the peptides to be available for elongation by the NRPS. A second level of molecular diversity comes into play via post-synthase modification. Examples of these activities include macrocyclization, heterocyclization, aromatization, methylation, oxidation, reduction, halogenation, and glycosylation. Finally, a third level of diversity can occur in which molecules from disparate secondary metabolic pathways may interact, such as the modification of a natural product by an isoprenoid oligomer. Here, we will cover only a small subsection of... 

Halocarbons, ketone-alcohol reduction, 84 Halogenation, 4-methylbenzyl chloride [reductive halogenation of aldehyde to benzyl chloride], 124 Hemiacetals, reduction of, 97-99 Hemiaminals, reduction of, 99-100 Hemiketals, reduction of, 97-99 Heptene derivatives, alkene to alkane reductions, disubstituted alkenes, 36-38... 

Unit operations are almost entirely physical in nature - for example, distillation, filtration, grinding, crystallization, etc. Chemical unit processes on the other hand, are the common standardized processes used in the chemical industry - for example, oxidation, reduction, halogenation, hydration, nitration, esterification, etc. 

The above-mentioned sulfoxides and sulfones have an acidic character (cf. their UV-spectroscopic behavior, Section III,A,2,c) and are stable to alkali. Unlike sulfones, however, sulfoxides are unstable to acids or to heating and undergo reductive halogenation on treatment with hydrobro-mic acid (66BCJ1988). 

The carbonyl group in aromatic esters, ketones and acids is transformed into aralkyl bromides or iodides by a one-pot reductive halogenation using LiAlH4/HX reagents (equation 155)988. 

Reactions of the Phenazathionium Cation with Unoxygenated Agents The Reductive Halogenation ... 

It is now established that the orientation of the reductive halogenation is controlled by nitrogen positions 3 and 7 are occupied first, then 1 and 9. Thus Schmalz and Burger obtained 3-chloro-lO-methyl-phenothiazine (45) from lO-methylphenothiazine-5-oxide (44) and hydrochloric acid, and 3,7-dichloro-lO-methyl-phenothiazine (47)... 

The mechanism of the reductive halogenation is still controversial. Two types of mechanism have been invoked.The first involves the formation of phenazathionium halides, followed by the nucleophilic attack of the halide ion. The second consists of an oxidation of the acid by the sulfoxide oxygen the halogen thus formed electrophilically attacks the reduced phenothiazine. 

We believe that, in the reductive halogenation, the halogens almost certainly enter the phenothiazine ring via both of the mechanisms discussed above. 

Aryl amine intermediates for azo and triphenylmethane dyes, as well as a number of vat dye (anthraquinone) intermediates, are made from compounds such as benzene, alkyl benzenes (toluene and higher homologues), phenol and naphthalene. A limited number of reactions are used to produce the most important dye intermediates, including nitration, reduction, halogenation, sulfonation, /V-alkylation, /V-acylation and alkali fusion33,34. 

Perfluoroalkyl anions can, in principle, be generated by the same methods as "normal alkyl or aryl anions - either by deprotonation of a suitable CH-acidic precursor by a strong base or by reductive halogen (usually iodine or bromine) metal exchange (Scheme 2.109). Another method - unique to the "perfluoro world -is addition of fluoride ions or other anions to perfluoroolefins. 

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