Displacement of chlorine atom

A typical nucleophilic displacement of chlorine atom in several 3-acyl-2,5-diaryl-2,3-dihydro-l,3,4-oxadiazoles by O- or /V-nuclcophilcs resulted in the formation of new 3-acyl derivatives (Equation 11) <2001JME4416>. 

Diazotization routes are mainly suited to the production of fluoroaromatics with only one or two fluorine atoms in the same ring. Two Or more fluorine atoms are often introduced via the nucleophilic displacement of chlorine atoms in an activated , i.e. electron-deficient, ring by fluoride ions. For example, the reaction of 2,4-dichloro-l-nitrobenzene with potassium fluoride has been used in the manufacture of 2,4-difluoro-l-nitrobenzene, an intermediate for the antiinflammatory aspirin derivative diflunisal (7). 

Displacement of chlorine atoms in chloropurines by other halogens, especially fluorine and iodine, is of value in the preparation of these derivatives. 

Nucleophilic displacement of chlorine atoms in pyrimido[5,4-t/]pyrimidines can also be achieved using iodide213,226 and azide ion.232 Thus, 2,6-dichloro-4,8-diiodopyrimido[5,4-[Pg.398]

An example of a A - <1996JA11978> and two examples of A -l,3,2-diazaphosphinines <2002PS2199, 2003PS2127> have been reported. These reactions proceed through successive displacements of chlorine atoms from PCI3 (for A -phosphorus) and PCls (for A -phosphorus). Further displacement of chlorine atoms leads to... 

In addition to the nucleophilic substitution of hydride atom from quinolines and isoquinolines, a reaction of high value for introduction of variety of substituents is the nucleophilic displacement of leaving groups on the heterocycle. As an example, 4-chloro-8-trifluoromethylquinoline reacts in a nucleophilic displacement of chlorine atom with methyl anthranilate, to provide the precursor of NS AID antihacterial flocatfenine. ... 

These trihalogenocyclopropenium salts react with benzene [55] or with thiophene [56] by displacement of chlorine atoms, e.g. 

Nucleophilic displacement of chlorine atoms with the fluoride ion is undoubtedly one of the most common methods to obtain fluorinated quinohnes from their chloro analogues. For instance, treattnent of perchloroquinoline with cesium fluoride in DMSO at 100° has resulted in a mixture of 2-fluoro-3,4,5,6,7,8-hexachloroquinoline, 4-fluoro-2,3,5,6,7,8-hexachloroquinoline, 4,5-difluoro-... 

Scheme 25 Nucleophilic displacement of chlorine atoms with the fluoride ion...

The reaction of 4,5,6-trichloro-l,2,3-triazine 4 with potassium fluoride at an elevated temperatures provides fully substituted 4,5,6-trifluoro-l,2,3-triazine 2 in addition to compounds 5 and 6 with partial displacement of chlorine atoms (Scheme 7) [11], It is clear that yields of fluorinated products depend on the reaction conditions (Table 3) [11]. At temperatures of 150-200 °C replacement of one or two chlorine atoms take place. The polyfluorinated 1,2,3-triazines 2, 5 were obtained when using two-step process in 55-69 % yields. 

Another example illustrating utility of this approach is displacement of chlorine atoms in 3,5,6-trichloro-l,2,4-triazine which does occur in a melt of compound 17 with dry KF (Scheme 12) [20]. The conversion degree depends on the reaction conditions at450 °C the dominantproduct of the reaction proved to be 3,5,6-trifluoro-1,2,4-triazine 18, while 3-chloro-5,6-difluoro-l,2,4-triazine 19 was isolated as a minor product. 

Scheme 12 Displacement of chlorine atoms in 3,5,6-trichloro-l,2,4-triazine...

In the condensation polymerization of chlorophenylsulfonyl phenoxide, increased reactivity of the polymer end group was demonstrated by the relation between conversion and reaction time (Scheme 3). Furthermore, comparison of the rate constants for the displacement of chlorine atoms with hydroxide showed that a model of the polymer end group reacted 20 times faster than the monomer. Thus, the electronic effects of a substituent in one ring were transmitted to the other via the sulfone linkage [5]. 

The amino group of 2-imino-3-phenyl-4-amino-5-carbethoxy-A4-thiazoline is very reactive and displaces the chlorine atom of various 2-chlorothiazoles (1577). 

Phosphites. Tertiary phosphites are also commonly used and are particularly effective ia most mixed metal stabilizers at a use level of 0.25—1.0 phr. They can take part ia a number of different reactions duting PVC processing they can react with HCl, displace activated chlorine atoms on the polymer, provide antioxidant functionaHty, and coordinate with the metals to alter the Lewis acidity of the chloride salts. Typical examples of phosphites are triphenyl phosphite [101 -02-0], diphenyl decyl phosphite [3287-06-7], tridecyl phosphite [2929-86-4], and polyphosphites made by reaction of PCl with polyols and capping alcohols. The phosphites are often included in commercial stabilizer packages. 

Using sulfur trioxide plus chlorine, or sulfur dioxide plus chlorine, sulfur monochloride yields thionyl chloride [7719-09-7] SOCI2. Various nucleophilic reactions can displace the chlorine atoms of sulfur monochloride ... 

CASRN 106-40-0 molecular formula CeHeBrN FW 172.02 Chemical/Physical. Hypochlorous acid reacted with p-bromoaniline forming bromochloro-aniline, bromodichloroaniline, dibromoaniline, and dibromochloroaniline. The displacement of bromine atom by chlorine yields hypobromous acid which then displaces a hydrogen atom from another brominated compound forming additional brominated compounds, e.g., bromochloro-aniline, bromodichloroaniline, etc. (Hwang et al., 1988). 

Aa the diaoid alcohols contain two atoms of hydroxyl, it folbws that there are two daeses of haloid ethers derivable from them. The first is formed by the substitution of one of the hydroxyl atoms by chlorine, bromine, o., and the second by the like displacement of both atoms of hydroxyl... 

This reaction has been studied in the case of aniline, which loses bade energy by the successive displacement of two atoms of hydrogen, and fii y becomes neutral by the sabstitutdon of three atoms of chlorine or bromine for thrra of hydrogen —... 

Displacement by chlorine atoms has also been observed on illumination of a carbon tetrachloride solution of diphenyl sulfone and excess chlorine. However, phenyl-, and methyl benzenesulfonates showed no displacement. The following mechanism is proposed for the reactions ... 

The first reaction stage is undoubtedly SN2 nucleophilic displacement of chlorine by the ethyl acetoacetate anion. Chlorine bond to carbon is weaker than that of fluorine. The resulting ethyl 5-fluoropentan-2-one-3-carboxylate subsequently cyclizes by an SNi reaction, displacing this time the fluorine atom [73]. 

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