Primary aromatic amines chlorinated

Isocyanates and amines react together to form ureas. Primary aliphatic amines react very quickly at temperatures down to ambient, whereas secondary aliphatic and primary aromatic amines react less quickly. The reaction rate of secondary aromatic amines is the slowest. The speed of the reaction can further be modified by the addition of substitutes near the amine group. The control of the speed can either be electronic, as illustrated by the effect of the chlorine in the MOCA ring, or by stereo chemical influences where the groups next to the amine group have a very strong hindrance to the curing. This is... 

When primary aromatic amines are treated with sulphur monochloride (8202 > also known as disulphur dichloride)—the Herz reaction—one or more products may be formed. One of these, the benzothiazathiolium salt, on treatment with nitrous acid gives the benzothiadiazole. Depending on the type of substitution in the ring, it is possible to obtain a good yield. The benzene ring may be chlorinated simultaneously, and the thiadiazole may possibly rearrange to another five-membered ring. 

If the /7-position of the amine is blocked by methoxy, methyl, chlorine or bromine groups, the species is stable with respect to dimerisation and higher anodic potentials are required for its further oxidation. However, further decomposition of the tri /7-anisylamine radical cation occurs in the presence of any traces of cyanide ion present in the acetonitrile solution. Primary aromatic amines, like phenols, tend to polymerise upon oxidation unless the o and p positions are blocked. 2,4,6-tri-t-butylaniline in acetonitrile solution yields a fairly stable radical cation which in the presence of water forms 3,5-di-f-butyl-4-amino-2,5-cyclohexadienone. ° ... 

This reaction is reported to proceed at a rapid rate, with over 25% conversion in less than 0.001 s [3]. It can also proceed at very low temperatures, as in the middle of winter. Most primary substituted urea linkages, referred to as urea bonds, are more thermally stable than urethane bonds, by 20-30°C, but not in all cases. Polyamines based on aromatic amines are normally somewhat slower, especially if there are additional electron withdrawing moieties on the aromatic ring, such as chlorine or ester linkages [4]. Use of aliphatic isocyanates, such as methylene bis-4,4 -(cyclohexylisocyanate) (HnMDI), in place of MDI, has been shown to slow the gelation rate to about 60 s, with an amine chain extender present. Sterically hindered secondary amine-terminated polyols, in conjunction with certain aliphatic isocyanates, are reported to have slower gelation times, in some cases as long as 24 h [4]. 

Chlorine is displaced from 24 (Scheme 33) by reaction with primary and secondary aromatic amines to yield 131, although reaction with 2-... 

Chlorocyclophosphazenes are quite reactive towards nucleophiles such as amines, alcohols or phenols. Complete replacement of chlorines is readily possible with a number of reagents. For example, the reaction of N3P3CI6 or N4P4CI8 with dimethylamine can lead to the formation of N3P3(NMe2)e or N4P4G e2) (see Eqs. 3.12 and 3.13). These reactions also work quite well with primary, secondary and even aromatic amines although individual differences in reactivity are present. 

In contrast to this imide-based synthesis, amides of the type RC(0)NH2 are decarbonylated to primary amines (RNH2) with chlorine in the presence of base. This process, often called the Hofmann reaction, involves an intermediate isocyanate (R-N = C = 0) (Fieser and Fieser, 1961 Sandler and Karo, 1983). Aromatic oximes, lacking an a-hydrogen, react with chlorine to form intermediates that are converted to nitrile Af-oxides with base. (Nitrile N-oxides are highly reactive species.)... 

In the last step we return to the original question of chemoselectivity Only the primary amine in 26 reacts because it is more nucleophilic than OH and because the more nucleophilic tertiary amine adds reversibly - it cannot lose a hydrogen atom as it does not have one. Only the 4-chlorine atom in the pyridine 28 reacts, presumably because addition to the other position would require the disruption of both aromatic rings. Though this compound has been succeeded by better anti-malarials, its synthesis illustrates the all-important principle that predictions of chemoselectivity must be based on sound mechanistic understanding. If doubt remains it is worth trying a model reaction on simpler compounds or, of course, an alternative strategy. 

The kinetics of the reactions of many xenobiotics with hydroxyl and nitrate radicals have been examined under simulated atmospheric conditions and include (1) aliphatic and aromatic hydrocarbons (Tuazon et al. 1986) and substituted monocyclic aromatic compounds (Atkinson et al. 1987c) (2) terpenes (Atkinson et al. 1985a) (3) amines (Atkinson et al. 1987a) (4) heterocyclic compounds (Atkinson et al. 1985b) and (5) chlorinated aromatic hydrocarbons (Kwok et al. 1995). For PCBs (Anderson and Hites 1996), rate constants were highly dependent on the number of chlorine atoms, and calculated atmospheric lifetimes varied from 2 days for 3-chlorobiphenyl to 34 days for 2,2, 3,5, 6-pentachlorbiphenyl. It was estimated that loss by hydroxylation in the atmosphere was a primary process for removal of PCBs from the environment. It was later shown that the products were chlorinated benzoic acids produced by initial reaction with a... 

The halogen of alkyl halides is generally readily susceptible to replacement by the —NHi group, but aromatically bound halogen usually requires more drastic treatment. Because of economic considerations, the chlorine derivatives are ordinarily employed, but bromine-substituted compounds are sometimes used because they usually lead to ithe formation of primary amines of higher purity under milder operating conditions. 

Imidazoles.—Formation. Several new syntheses of imidazoles from isocyanides have been reported these include the formation of 1-alkyl-imidazoles (396) by the action of primary amines on 2-isocyano-2-tosylstyrene, PhCH=C-(NOTos, the cyclization of the enamine Me2NCH=C(NC)C02Me to compound (397) in the presence of methyl iodide,and the preparation of the ethers or thioethers (398) from isocyano-cyanides R CH(NC)CN by their reaction with alcohols or thiols R XH, respectively.Aromatic aldehydes are converted into 2-aryl-4,5-dichloroimidazoles (399) by the combined action of cyanogen and hydrochloric acid. 5-Acetyl-4-methylimidazole (400) results when form-amido-acetylacetone, AC2CHNHCHO, is heated with formamide and formic acid. Exhaustive chlorination of tetramethyldithio-oxamide leads to the tri-chloro-imidazolium cation (401). ... 

Formula (CH3)2CH0C(0)00C(0)0CH(CH3)2 Properties Colorless cryst. solid or liq. misc. with aliphatic, aromatic, and chlorinated hydrocarbons, esters, ethers pract. insol. in water m.w. 206.22 dens. 1.080 (15.5/4 C) m.p. 8-10 C rapid decomp. 63 F ref. index 1.4034 (20 C) Toxicology LD50 (oral, rat) 2140 mg/kg, (skin, rabbit) 2025 mg/kg mod. toxic by ing. and skin contact primary severe eye irritant TSCA listed Precaution Dangerous fire risk unstable above IOC impact- and heat-sensitive explosive spontaneous decomp. R.T. releases flamm. and corrosive prods. explodes on heating explodes on contact with amines or potassium iodide, possibly organics Hazardous Decomp. Prods. Heated to decomp., emits acrid smoke and fumes NFPA Health 0, Flammability 4, Reactivity 4 Storage Store in open containers low temps, with adequate ventilation Uses Low-temp, polymerization catalyst initiator for polymerization of unsat. monomers, PVC in food-pkg. adhesives polymerization catalyst in mfg. of paper/paperboard in contact with aq./fatty foods... 

---