2,3,5,6-Tetrachloro-4 pyridine

Beilstein Handbook Reference) BRN 0129639 EINECS 219-283-9 HSDB 5874 NSC 2009 Pyridine, 2,3,5,6-tetrachloro- 2,3,5,6-Tetrachloropyr-idine Tetrachloropyridine,... 

An extensive study of the amination of halopyridines has been carried out by den Hertog and co-workers.A comparison of their results with studies in inert solvents using primary and tertiary amines should permit some evaluation of the postulated factors. 2,4-Dichloropyridine in concentrated aqueous ammonia (180°, 5 hr) resulted in the formation of 4-amino- (60% yield) and 2-amino-chloropyridines (20% yield). Under similar conditions, only 4-substitution of 3,4,6-trichloro- and of 2,3,4,5-tetrabromo- and -tetrachloro-pyridines was observed. However, in these and the other polyhalo pyridines, the appreciable and unequal mutual activation by the halogen substituents needs to be emphasized. 

Since the nitrogen in pyridine is electron attracting it seemed reasonable to predict that the trihalopyridynes would also show the increased electrophilic character necessary to form adducts with aromatic hydrocarbons under similar conditions to those employed with the tetra-halogeno-benzynes. The availability of pentachloropyridine suggested to us and others that the reaction with w-butyl-lithium should lead to the formation of tetrachloro-4-pyridyl-lithium 82 84>. This has been achieved and adducts obtained, although this system is complicated by the ease with which pentachloropyridine undergoes nucleophilic substitution by tetrachloro-4-pyridyl lithium. Adducts of the type (45) have been isolated in modest yield both in the trichloro- and tribromo- 58) series. 

Diethylamino-5-phenyl-l,2,4-dithiazolium tetrachloro-(or bromo)nickelate (10) decomposes in protic (H2O, EtOH) and strongly coordinating solvents (DMF, DMSO, MeCN, pyridine) in which it is soluble. It can be stored in a dessicator or a sealed tube from a month to a year <89ZAAC(576)203>. 

An interesting application of the reaction with sulfuryl chloride consisted in the synthesis of a fully chlorinated hexoside.27 Treatment of methyl 2-chloro-2-deoxy-/3-D-galactopyranoside with sulfuryl chloride and pyridine in chloroform, followed by heating of the product with an excess of pyridinium chloride, afforded a tetrachloride, presumably methyl 2,3,4,6-tetrachloro-2,3,4,6-tetradeoxy-/3-D-allopy-ranoside. 

Treatment of sucrose with sulfuryl chloride in pyridine at 50° afforded443 a complex mixture of products from which were isolated, in low yields, one tetrachloro and two pentachloro derivatives. 

Sulfanyl groups are active substrates for perfluorodecarboxylation reactions. 2,3,5,6-Tetra-chloro-4-sulfanylpyridine reacts with xenon difluoride and perfluoroalkanecarboxylic acids in dichloromethane at room temperature to form 2,3,5,6-tetrachloro-4-perfiuoroalkylsulfanyl-pyridines in moderate to high yields.87... 

Less commonly used solvents include methyl ethyl ketone, b.p. 80° ethylene chloride, b.p. 84° dioxan (diethylene dioxide), b.p. 101° (vapours are toxic) toluene, b.p. 110° pyridine, b.p. 115-5° chlorobenzene, b.p. 132° cellosolve (ethylene glycol monoethvl ether), b.p. 134-5° di- -butyl ether, b.p. 141° s-tetrachloro-... 

Miscellaneous compounds l-(3-Chloroallyl)-3,5,7-triaza-l-azoniaadamantane chloride 2,3,5,6-Tetrachloro-4-(methyl-sulfonyl)pyridine... 

Finally, a valuable example of multistep modifications of sucrose is the synthesis of Sucralose (l Ab -trideoxy-l Ab -trichloro-tya/flcm-sucrose)—a compound 650 times more sweeter than sucrose,15,326,327 which was obtained by treatment of 6-O-acetylsucrose with sulfuryl chloride in pyridine. Further reaction of this derivative with triphenylphosphine and diethyl azodicarboxylate afforded an epoxide from which a tetrachloro-derivative... 

Dimethoxypropylamino)-3-nitro-6-(2,2,2-trifluoroethoxy)pyridine (30) gave 8-nitro-5-(trifluoromethoxy)-l,2-dihydro-l,6-naphthyridine (31) (85% H3PO4, 100°C, 2 h 776%), which was aromatized in unstated yield (tetrachloro-l,4-benzoquinone, CHC13, reflux, 2.5 h).1116... 

Likewise, tetrachloro-l,2-dimethyldisilane reacts with bis(trimethylsilyl)carbodiimide to give Si/C/N gels. In the reaction of methyltrichlorosilane with bis(trimethylsilyl)carbodi-imide in the presence of pyridine, a highly crosslinked ceramic precursor is also obtained." ... 

Majima and Simanuki found that meso-inositol reacts with thionyl chloride only in the presence of pyridine. Among the products isolated was a monochloro-desoxy-inositol, a tetrachloro-tetradesoxy-inositol, a tri- and a tetrachlorobenzene and a tri- and a tetrachlorophenol. 

Derivatives of 138 and some heptacyclic analogs were prepared from 2,3,5,6-tetrachloro-1,4-benzoquinone and phenols (57JOC342, 57MI2 60T135). When present, pyridine is incorporated into the newly formed molecule, and quinones like 144 were obtained (58MI2). 

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