2.8- dichloro-10,10-diiodo

The best known of the hahdes are the trialkyldihalo- and triaryldihaloantimony compounds. The dichloro, dibromo, and diiodo compounds are generally prepared by direct halogenation of the corresponding tertiary stibiaes. The difluoro compounds are obtained by metathasis from the dichloro or dibromo compounds and silver fluoride. The diiodo compounds are the least stable and are difficult to obtain ia a pure state. The tri alkyl- and triaryldichloro- and dibromoantimony compounds are all crystalline soHds which are stable at room temperature that but decompose on heating ... 

Imidazole, 4,5-dibromo-l-methyl-synthesis, S, 399 Imidazole, 4,5-di-t-butyl-synthesis, S, 483 X-ray diffraction, S, 350 Imidazole, 4,5-dichloro-chlorination, S, 398 synthesis, S, 398, 473 Imidazole, 4-(3,4-dichlorophenyl)-nitration, 5, 433 Imidazole, 4,5-dicyano-hydrolysis, S, 435-436 synthesis, S, 461, 472, 487 Imidazole, 4,5-dicyano-1-vinyl-synthesis, S, 387 Imidazole, 4,5-dihydro-mass spectra, 5, 360 Imidazole, 4-(dihydroxybutyl)-synthesis, S, 484 Imidazole, 4,5-diiodo-nitration, S, 396 synthesis, S, 400 Imidazole, 2,4-diiodo-5-methyl-iodination, S, 400 Imidazole, 1,2-dimethyl-anions... 

It is believed that equatorial substituents such as chlorine or bromine would increase the guest diameter beyond the allowed values (assuming that the guest molecules stack roughly parallel to the canal68)). Support for this comes from the study of fluorocyclohexane where the population of the axial conformer is not enhanced to any major extent70. Nitro-71) and cyano-cyclohexane, trans-l,2-dichloro-, trans-1,2-dibromo-, tram-1,4-dichloro-, trans-1,4-dibromo-, and trans-l-bromo-4-chloro-cyclohexane all pack most efficiently in the thiourea canals as the axial or diaxial conformer 68,72. Tram-2,3-dichloro-1,4-dioxane behaves similarly73. In contrast isocyanato-, tram-1,4-diiodo-, trans-1 -bromo-4-iodo-, and tram-1 -chloro-4-iodo-cyclohexane are present as mixtures of the axial/equatorial or diaxial/diequatorial conformations as appropriate 68,72). The reason for this anomalous behaviour of the iodosubstituted cyclohexanes is not clear. 

It is extremely shock-sensitive, a 4.0 kg cm shock causing detonation in 50% of test runs (cf. 3.5 kg cm for propargyl bromide 2.0 kg cm for glyceryl nitrate). The intermediate bis-chlorosulfite involved in the preparation needs low temperatures to avoid vigorous decomposition. The corresponding diiodo derivative was expected to be similarly hazardous [1], and this has been confirmed [2]. Improvements in preparative techniques (use of dichloromethane solvent at —30°C) to avoid violent reaction have also been described [3], An attempt to distill the compound (b.p. 55-58°C/0.6 mbar, equivalent to about 230°C/l bar) at atmospheric pressure from a heating mantle led to a violent explosion [4], The compound involved was erroneously given as l,6-dichloro-2,4-hexadiene [5],... 

The electrochemistry of cobalt-salen complexes in the presence of alkyl halides has been studied thoroughly.252,263-266 The reaction mechanism is similar to that for the nickel complexes, with the intermediate formation of an alkylcobalt(III) complex. Co -salen reacts with 1,8-diiodo-octane to afford an alkyl-bridged bis[Co" (salen)] complex.267 Electrosynthetic applications of the cobalt-salen catalyst are homo- and heterocoupling reactions with mixtures of alkylchlorides and bromides,268 conversion of benzal chloride to stilbene with the intermediate formation of l,2-dichloro-l,2-diphenylethane,269 reductive coupling of bromoalkanes with an activated alkenes,270 or carboxylation of benzylic and allylic chlorides by C02.271,272 Efficient electroreduc-tive dimerization of benzyl bromide to bibenzyl is catalyzed by the dicobalt complex (15).273 The proposed mechanism involves an intermediate bis[alkylcobalt(III)] complex. 

This pyridoxal-phosphate-dependent enzyme [EC 2.6.1.24] catalyzes the reversible reaction of 3,5-diiodo-tyrosine with a-ketoglutarate (or, 2-oxoglutarate) to generate 3,5-diiodo-4-hydroxyphenylpyruvate and glutamate. Also acting as substrates are the 3,5-dichloro, 3,5-dibromo, and the 3-iodo derivatives of tyrosine, as well as thyroxine and triiodothyronine. 

Chlorination of quinoline in the presence of silver sulfate in sulfuric acid gives 5-chloro, 8-chloro- and 5,8-dichloro-quinoline (63CI(L)1840, 66MI20601). Similarly, addition of iodine to quinoline and silver sulfate in sulfuric acid at 150-200 °C gives 5-iodo-, 8-iodo- and 5,8-diiodo-quinoline (Scheme 8). It is thought that I+ is the electrophile (64CI(L)1753, 66MI20602). 

The methine bridge in acridines can be derived from dihalomethanes. Originally sodium carbonate was used, with dichloro- or diiodo-methane, to prepare dibenzacridine (624) from 2-naphthylamine (02JCS280). Subsequently, better yields were obtained when dichloromethane, 1,1-dichloroethane or benzal chloride, 1-naphthylamine, and a solvent were heated, the products being dibenz(c,/z jacridines (624) (06JCS1387). 

The addition of dichlorocarbene, produced from CHCl3-NaOH in the presence of a phase transfer catalyst, to the 10,11-bond of 5//-dibenz[6,/]azepine is accompanied by formylation at nitrogen (78CPB942), whereas the A-methyl derivative with diiodo- or dichloro-methane and a zinc-copper catalyst forms the 10,11-cyclopropanoderivative (137 X = CH2, R = Me) in 55% yield (76CPB2751). 

Alkyldichlorophosphanes are converted by antimony(III) fluoride into alkyltetrafluoro-A5-phosphanes (RPF4, where R is Me,45,49 Et,45,49 i-Pr,50 allyl,49 Bu45) in 60-80% yield. With electron-withdrawing substituents at the phosphorus atom, e.g. in dichloro(pcntafluoro-phenyl)phosphane, dichloro(chloromethyl)phosphane, dichloro(trichloromethyl)phosphane, diiodo(trifluoromethyl)phosphane or with alkoxy or dialkylamino groups in ROPCl2,... 

The polymers prepared by Hunter from polyhalophenols were undoubtedly highly branched. He examined the decomposition of salts of 2.6-dibromo-4-chlorophenol, 2.6-dichloro-4-bromophenol and 2.6-diiodo-4-chlorophenol (44). By analysis of the resulting polymers he was able to determine qualitatively (Table 6) the order of reactivety of the halogens (I>Br>Cl) and furthermore established that considerable reaction occurs through the o-position. 

The reaction has been extended to a,a-dichloro-o-xylene [78JOM(146)245] and 2,3-bis(bromomethyl)quinoxaline [84JCS(D)23]. In both cases the addition of Nal was found to facilitate the cycliza-tion reaction. With l,8-bis(bromomethyl)naphthalene, l,l-diiodo-3,5-naphtho-1-telluracyclohexane 7 has been obtained by the reaction with Te and Nal in 2-methoxyethanol [88JOM(338)l]. 

For the cr-telluranes 94, one characteristic is the smooth exchange reaction at the tellurium center. 10,10-Dibromo(diiodo)phenoxatellurines convert to dichlorides when treated with chlorine or sulfuryl chloride 10,10-diiodo derivatives under the action of bromine readily afford 10,10-dibro-mides and 10,10-dichloro- and 10,10-dibromophenoxatellurines are easily transformed to 10,10-diiodo derivatives when potassium iodide is added to their methanolic solutions (70MI2). 

It is to be noted that further compounds in this series can be readily prepared. These include dichloro(dicyclo-pentadiene) platinum (II), chloromethoxy(dichloropenta-diene)platinum(II), and diiodo(dicyclopentadiene)plati-num(II). Adequate syntheses of these compounds have been given.8... 

Tetrapropylammonium dichloro-iodate(I), 5 172 Tetrapropylammonium diiodo-iodate(I), 5 172... 

Further enhancement of jt-stacked order can be achieved by the use of small electron-withdrawing substituents. The 9,10-dihaloanthracenes (dichloro [31], di-bromo [32] and diiodo [33]) all adopt a jt-stacked arrangement in the solid, with... 

The reaction of trimethylstannylsodium with two geminal dihalides, 6,6-dichloro-5,5-dimethyl-1-hexene and 6,6-diiodo-5,5-dimethyl-l-hexene, gave evidence of a single electron transfer pathway. An initial electron transfer from MetSn- to the geminal dihalides leads to the haloradical (X ), which then serves as the precursor to all the reactions and products detailed in Scheme 37195. 

R = Me)356, 2.336 A, in agreement with the lower Lewis acidity of diiodo with respect to dichloro and dibromo diorganotin species. 

The 1,2-dihaloethanes show a marked conformational sensitivity to physical state and medium137-142 (see Table 18). In the vapor phase, 1,2-difluoroethane is more stable in the gauche form but the dichloro, dibromo and diiodo compounds are more stable in the anti form. The gauche form is favored in the liquid state when at least one of the halogen atoms is fluorine, but in other instances the anti form is preferred. 

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