A-Halogen-amides

However, an exception must be made for those A-hydroxymethyl amides that derive from antimicrobial effective compounds having an amide configuration in the molecule, e.g. a-halogen-amides (introduction of a second toxophoric group into the molecule). 

The photochemical 1,2-addition of A -halogen amides to alkenes results in a mixture of diastereomers (equation 18). ... 

General information. DBNPA is a halogenated amide and is considered a fast kill biocide. It has seen widespread use in water treatment and pulp and paper applications but in the oilfield is used primarily to treat the water used to prepare fracturing fluids. Its main attribute seems to be that its biocidal action is very fast, but the active then hydrolyzes to less toxic by-products. This may be advantageous in applications where water is stored prior to discharge so deactivation may not be necessary. 

Primary a-halogenated amides - absorb at higher frequencies than the corresponding alkyl compound, up to about 1750 cm (5.71 gm), and may, in fact, have two carbonyl bands due to the presence of rotational isomerism. The carbonyl band of A -halogen secondary amides also occurs at higher frequencies than that of the corresponding A -alkyl compound. 

The O-S exchange method in presence of a-halogenated carbonyl compound is a very good one for thiazole compounds. The thioamide is prepared in situ by the action of amide upon phosphorus pentasulphide with solvent. The a-halogenated aldehyde reacts directly. But the O-Se exchange cannot be performed with a-halogenated carbonyl compounds because of the apparition of phosphoric acid. (Scheme 3), The C-Se bond is very sensitive to add pH. 

A/-Chloro fatty acid amides have been synthesized from the direct halogenation of the amide in boiling water (28). They are useful as reactive intermediates for further synthesis. Fluorination has also been reported by treating the fatty amide with fluorine-containing acid reagents at 200 °C to reach a fluorinated amide with less reactivity toward fluorocarbon polymers (29). 

A -Halogenated compounds such as iV-chlorotnfluoroacetamide, A -chloro-imidosulfuryl fluonde and N N dichlorotnfluoromethylamine add across C=C bonds to form saturated amides [14] tmidosulfury I fluorides [15] and amines [16], respectively Allylic halogenation also occurs with the use of A-bromo- or A-chIo roperfluoroamides The primary amine A,A-dichlorotrifluororaethylamine selectively affords 11 or 2 1 adducts with either tetrafluoroethylene or chlorotrifluoroethylene [16] (equation 7) The reaction mechanism is believed to involve thermal free radicals, with control achieved principally by reaction temperature The 1 1 adduct is formed even in the presence of a large excess of olefin... 

A classical procedure for the synthesis of the A-(1-chloroalkyl)amides1 or carbamates68 involves substitution of the hydroxy group in stable A-( 1-hydroxyalkyl)amides (or carbamates) by a halogen function with reagents such as thionyl chloride, phosphorus pentachloride, phosphorus pentabromide, etc. In certain cases merely heating in concentrated hydrochloric or hydrobromic acid suffices1. 

Several min after addition of ethanol to a mixture of the amide chloride ( fusible white precipitate ) and iodine, an explosion occurs. Addition of the compound to chlorine gas or bromine vapour leads to a delayed violent or explosive reaction. Amminemetal salts behave similarly, and formation of A-halogen compounds is involved in all cases. 

A-Halogeno-amides are familiar and convenient sources of positive halogen for the organic chemist, and the 2 1 complex formed in benzene between diazabicyclooctane (DABCO) and /V-bromsuccinimide (NBS) [48] (the numbers are the observed interatomic distances in angstroms) in effect shows one such reagent in action (Crowston et al., 1984). The N-Br-N angle is close to linear [175.1(2) A], and the bromine is poised almost midway between the two nitrogen atoms, which are of similar basicity. The... 

The mechanism of this remarkable reaction, in which a halogen atom in a tertiary acetylenic halide is substituted by the nucleophilic group NH2 with high yields, is not completely dear. Probably the ethynyl hydrogen atom is abstracted in the first step by the strongly basic amide. The results from solvolysis experiments carried out with tertiary acetylenic bromides [22] suggest that the intermediate -C C-C(CH3)2C1 looses CP to give the Zwitter-ionic intermediate C=C-C+(CH3)2. This is subsequently attacked by NH3 or-NH2. 

A number of other methods exist for the a halogenation of carboxylic acids or their derivatives.134 The acids or their chlorides or anhydrides can be a chlorinated by treatment with CuCl in polar inert solvents (e.g., sulfolane).135 Acyl halides can be a brominated or chlorinated by use of N-bromo- or N-chlorosuccinimide and HBr or HC1.136 The latter is an ionic, not a free-radical halogenation (see 4-2). Direct iodination of carboxylic acids has been achieved with L-Cu(II) acetate in HO Ac.137 Acyl chlorides can be a iodinated with L and a trace of HI.138 Carboxylic esters can be a halogenated by conversion to their enolate ions with lithium N-isopropylcyclohexylamide in THF and treatment of this solution at - 78° with I2138 or with a carbon tetrahalide.139 Carboxylic acids, esters, and amides have been a fluorinated at -78°C with F2 diluted in Ni.,4°... 

HOFMANN S REACTION. Reaclion used lor preparation of a primary amine from an amide by treatment with a halogen (usually bromine) and caustic soda. The resulting amine has one fewer carhon atom than the amide used. 

Currently the most popular of the pseudohalides are N-haloamides. These reagents are used in conjunction with the solvent or an added nucleophilic reagent to give overall 1,2-addition of a halogen and a nucleophile to the alkenic substrate. The amides of choice seem to be N-halosuccinimides. The low nu-cleophilicity of the succinimdyl anion allows for a variety of nucleophiles to attack the initially formed halonium ion. 

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