Elimination of hydrogen chloride

Present in citronella and valerian oils, tur penline, ginger, rosemary and spike oils. It is produced artificially by the elimination of hydrogen chloride from bornyl chloride (artifi cial camphor) or from isobornyl chloride, by the dehydrogenation of borneol and isobor-neol and by the action of elhanoic anhydride on bornylamine. Chiral. 

The presence of the base brings about the irreversible elimination of hydrogen chloride between the acid chloride and the acid the resulting p3rridine hydrochloride precipitates out as the reaction progresses. 

The manufacture and uses of oxiranes are reviewed in (B-80MI50500, B-80MI50501). The industrially most important oxiranes are oxirane itself (ethylene oxide), which is made by catalyzed air-oxidation of ethylene (cf. Section 5.05.4.2.2(f)), and methyloxirane (propylene oxide), which is made by /3-elimination of hydrogen chloride from propene-derived 1-chloro-2-propanol (cf. Section 5.05.4.2.1) and by epoxidation of propene with 1-phenylethyl hydroperoxide cf. Section 5.05.4.2.2(f)) (79MI50501). 

Diaziridinones (167) are obtained from di-t-alkylureas by Af-chlorination and base-promoted elimination of hydrogen chloride from (279) (69JOC2254). The very unstable c/s-fused diaziridinone (280) could be prepared by a similar but milder procedure (76JOC2813). 

Dehydrochlorination begins at about 120°C. The temperature is raised about lO C/hr to 150 C to avoid vigorous gas evolution. The elimination of hydrogen chloride is complete after 5-6 hr. 

Note 1. An alternative procedure proceeds by oxidation of the 3/5-hydroxy group with chromic acid-sulfuric acid and subsequent elimination of hydrogen chloride by treatment of the intermediate chloroketone with potassium acetate in methanol. Good overall yields are obtained with this reaction sequence in the androstane series. 

Elimination of hydrogen chloride from 1,1-dichloromethyl sulfide with potassium tcrt-butoxide affords chloromethylthiocarbene [J] (equation 5)... 

Dehydrochlorination of bis(tnfluoromethylthio)acetyl chloride with calcium oxide gives bis(trifluoromethylthio)ketene [5] (equation 6) Elimination of hydrogen chloride or hydrogen bromide by means of tetrabutylammonium or potassium fluoride from vinylic chlorides or bromides leads to acetylenes or allenes [6 (equation 7) Addition of dicyclohexyl-18-crown-6 ether raises the yields of potassium fluoride-promoted elimination of hydrogen bromide from (Z)-P-bromo-p-ni-trostyrene in acetonitrile from 0 to 53-71 % In dimethyl formamide, yields increase from 28-35% to 58-68%... 

Elimination of hydrogen chloride from 2/f perfluoro-2-methylpropane-1 -sulfenyl chloride by the triethylamine-boron trifluoride complex results in cyclization to perfluoro-l,l-dimethylthiirane (perfluoroisobutylene sulfide) [, 9] (equation 9)... 

The treatment of enamines with acid halides which possess no a hydrogens results in the simple acylation of the enamine (7,12,62-67). If the acid halide possesses an a hydrogen, however, ketenes are produced in situ through base-catalyzed elimination of hydrogen chloride from the acid halide. The base catalyst for this reaction may be the enamine itself or some other base introduced into the reaction mixture such as triethylamine. However, if the ketene is produced in situ instead of externally, there still remains the possibility of a side reaction between the acid halide and the enamine other than the production of ketene (67,84). 

Braun and Schurek [9] assumed that during polymerization a reaction can occur between the polymer and free radicals that leads to the elimination of hydrogen chloride and formation of a double bond. The formation of HCl during the polymerization of vinyl chloride has been observed [10],... 

Preliminary experiments on the coupling of the chloride (lb) with digitoxigenin (3/ ,14,/ -dihydroxy-5/ -card-20(22)-enolide) in the presence of silver carbonate, led to gross decomposition of the halide, and it was suspected that, under the conditions of the experiments, the silver carbonate was causing elimination of hydrogen chloride. When, however, digitoxigenin was treated with an excess of lb in a small volume of... 

Addition of benzoyl chloride to 2.5-dimethyl-3,4,6-triphenyl-3//-azepine (13) in benzene in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) leads to elimination of hydrogen chloride and formation of the 2-methylene-l//-azcpine 14.117 All attempts to isomerize the methylene derivative to 1-benzoyl-2,5-dimethyl-3,4,6-triphenyl-l//-azepine under basic conditions failed. Analogous reactions can occur with 2,5-dielhyl-3,4,6-triphenyl-3//-azepine. 

The synthesis of enantiomerically pure propargylic alcohols is possible using the same methodology 43b. Thus, addition of (—)-[(l-chloro-2-phenylethyl)sulfinyl]-4-methylbenzene (14) to propan-al led to a mixture of the diastereomers 15A/15B (d.r. 44 56) which are easily separated by column chromatography. After thermal elimination of the sulfinyl group the vinyl chlorides 16A/16B were obtained as a mixture of E- and Z-oleftns. Elimination of hydrogen chloride was carried out with three equivalents of butyllithium, leading to enantiomerically pure 1 -phenyl-1-pentyn-3-ol. 

In the course of work on the mechanism of elimination reactions, the author and his co-workers have measured reaction-rate constants for the second-order elimination of hydrogen chloride from six dichloroethyl compounds of type Ar2CHCHCl2 and three monochloroethyl compounds of type Ar2CHCH2Cl (7). Samples of each of these materials were furnished to the Bureau of Entomology and Plant Quarantine for insecticidal testing, and the author is indebted to C. C. Deonier and I. H. Gilbert for permission to use certain of their data in this paper. The rate constants and larvicidal results are given in Table I. 

Chlorohydroxyacetylene, or the isomeric chloroketene, or chlorooxirene may have been formed by elimination of hydrogen chloride. 

While r 2-coordination of silanimines has been realized in species such as Cp2Zr(r 2-SiMe2=Nt-Bu)(PMe3) [13], no -(silanimine) transition metal complexes are known so far [14 - 16]. Access to these Si=N systems is opened up by treatment of 19b,c with Me3P=CH2 at low temperature leading to elimination of hydrogen chloride and formation of the fert-butyl and mesityl-N-derivative 23a,b. These species are stable only for a short period in solution (two hours in toluene at -30°C), but can be... 

The most widely applied precursors for the synthesis of monocyclic NHPs are a-diimines which can be converted to the target heterocycles either in a two-step reaction sequence involving two-electron reduction of the diimine to an enediamide, enediamine, or a-aminoamine and subsequent condensation with PC13 [18-20] or a dichlorophosphine RPC12 [21], or via direct base-promoted reaction with PC13 [20, 22], The latter reaction involves addition of a P-Cl bond to each imine moiety followed by base-promoted elimination of hydrogen chloride leading to 2,4-dichloro-... 

Dichlorocarbenes can be synthesized by the a elimination of hydrogen chloride from chloroform. 

A more complex cumulenyl carbenoid 80 may be generated in situ from 1,4-dihalobut-2-ynes and two equivalents of base (Scheme 3.21). Insertion into organozirconocene chlorides gives allenyl zirconium species 81, which are regioselectively protonated to afford enyne products 82 [38], The stereochemistry of the alkene in 82 stems from the initial elimination of hydrogen chloride to form 80. 

The reaction of a fourfold excess of aryldiazomethanes 130 with dichlorosulfine leads to 3,5-diaryl[l,2,4]triazolo[5,l+]-[l,3,4]thiadiazole-4-oxides 131. The formation of the fused heterocycles 131 is rationalized on the basis of two consecutive cycloaddition steps, each followed by elimination of hydrogen chloride promoted by the excess of aryldiazomethane (Scheme 9) <1984JCM175>. 

This reaction is similar of course to the corresponding elimination of hydrogen chloride from H sulphone9 to give divinyl sulphone ... 

Though the PECH decomposes to indefinite fragments with n-butyl lithium or sodium hydride in THF at room temperature, it reacts with sodium methoxide with liberation of Cl in which the -elimination of hydrogen chloride predominates instead of nucleophilic substitution. For instance, PECH in DMSO was reacted with double the molar quantity of sodium methoxide at room temperature for 24 h to give the unsaturated polyether (DS 92.3%,v(C=C) 1630,5 (=CH2) 795 cm" ) after purification by dissolution(DMF)-precipitation (H20) technique. A similar unsaturated polyther was obtained by the pyrolysis of the sulfilimine 13 (110-130°C) but not of sulfoxide 12 (100-150°C). When the polymer 26, was heated to 90°C, the absorption of C=C and =CH2 decreased and a new absorption at 1720 cm appeared and increased. This is explained as a result of [3.3] sigmatropic rearrangement of to afford including C=CH2 and C=0 structure as shown in equation 7. 

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