Halogen derivatives chloro

Certain halogen derivatives of 8-hydroxyquinoline have a record of therapeutic efficacy in the treatment of cutaneous fungus infections and also of amebic dysentery. Among these are 5-chloro-7-iodo-8-quinolinol [130-26-7] (iodochlorhydroxyquin, Vioform), 5,7-diiodo-8-hydroxyquinoline [83-73-8] (diiodohydroxyquin), and sodium 7-iodo-8-hydroxyquinoline-5-sulfonate [885-04-1] (chiniofon) (196—198). 

Certain polar substituents at the 4-position of 2,5-DMA render the eompounds inaetive for example, the 4-COOH and 4-OH derivatives do not produee DOM-like effeets. On the other hand, 4-halogenated compounds result in relatively potent derivatives. The 4-fluoro derivative DOF is 4 times more potent than 2,5-DMA. whereas the 4-chloro (DOC) and 4-iodo (DOI) analogs are about 20 times more potent than 2,5-DMA. The most potent halogenated derivative is the 4-bromo analog DOB, which is about 40 times as potent as 2,5-DMA. 

Detailed investigations of the chemical reactivity of the diketiminato-stabilized phosphenium cations like 28 (Scheme 17) are to date rare and include only two reports dealing with the substitution and reduction of P-halogen-derivatives. Thus, reaction of 28 (X=Br) with sodium hydroxide in toluene was reported to proceed with displacement of the halide substituent at phosphorus and conservation of the heterocyclic ring to give a mixture of bromide and triflate salts containing a P-hydroxy-substituted cation, both of which were isolated in small yields [89], The products are remarkable as they represent one of very few examples of a stable phosphinous acid which does not rearrange to the tautomeric secondary phosphine oxide. Potassium reduction of the P-chloro-substituted derivative 34 produced the... 

Although N-halogenated pyrazoles are known, they are quite unstable compounds, increasing in stability from chloro to iodo. They may be implicated in the formation of poly halogenated derivatives (76MI2). There are many examples of competition between nuclear and side-chain halogenation, particularly when radical species can form (90CHE301). 

Other stable diazoalkanes, such as diazoketones, can also be converted into halogen derivatives, as illustrated by the conversion of 3,4-di-O-benzoyl-l-deoxy-l-diazo-D-g/t/cero-tetrulose into the 1-bromo- and 1-chloro-deoxy derivatives by the action of hydrogen bromide and hydrogen chloride, respectively.196... 

Thieno[3,2-c]pyridin-4-one (277) has been prepared by thermal cyclization of 2-thienyl-vinyl isocyanate (Scheme 73) (70BSB301). The derived chloro compound (278) can either be reduced by zinc-acetic acid to (260) or be readily converted into other derivatives by nucleophilic substitution of the halogen. The formation of 4-thiomethyl-6,7-dihydro-thieno[3,2-c]pyridine (280) by cyclization of the isothiocyanate (279) has also been reported (equation 23) (73GEP2318399). 

A special reaction of a halogen derivative is the 2F/mol reduction of 1,4-dichlor-ophthalazine which leads to phthalonitrile and involves the cleavage of the two C-Cl bonds and the N-N bond 1-chloro-4-methoxyphthalazine is reduced similarly [486]. 

Bromo-and chloro- derivatives of 2-pyridylazo reagents are more sensitive. The 5-Br-PADAP method has already been described. Other halogen-derivatives used in determining cobalt are 2-(5-chloro-2-pyridylazo)-5-diethylaminophenol (5-Cl-PADAP, formula 18.4) (e = 1.06-10 ) [43], 2-(5-bromo-2-pyridylazo)-l,5-diaminobenzene (5-Br-PADAB) (formula 18.5) (e = 1.16-10 ) [44,45], 2-(3,5-dichloro-2-pyridylazo-5-dimethylaminophenol) (e = 8.4-10" ) [46], and 2-(3,5-dibromo-2-pyrldylazo)-5-dimethylaminobenzoic acid (e = 1.55-10 at 673 nm) [47]. 

Carbon-Halogen Bonds. Carbon-halogen bonds may be prepared directly via the lithio intermediate or a second intermediate prepared from the lithio intermediate. For example, reaction of hexachloroethane with 2-lithiodimethylaminomethylferrocene gave the chloro derivative (Reaction 16) (23). However, preparation of other halogen derivatives via lithio intermediates has not been successful. A better and more versatile method for preparing the chloro, bromo, and iodo derivatives involves isolating a boronic acid intermediate as in Reaction 17 (24). 

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