The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Hunsdiecker reaction of silver salts of cis- and trans-1,2-cyclohexanedicarboxylic acid》. Authors are Abell, Paul I..The article about the compound:cis-Cyclohexane-1,2-dicarboxylic acidcas:610-09-3,SMILESS:O=C([C@H]1[C@@H](C(O)=O)CCCC1)O).Application of 610-09-3. Through the article, more information about this compound (cas:610-09-3) is conveyed.
Decarboxylation of the Ag salts of cis- and trans-1,2-cyclohexanedicarboxylic acids (I, Ia) by the action of halogen according to Hunsdiecker, et al. (C.A. 38, 374), gave only trans-1,2-dibromocyclohexane (IIa) through isomerization which appeared to take place at an intermediate stage in the reaction. Com. cis-1,2-cyclohexanedicarboxylic anhydride hydrolyzed in boiling H2O gave I, m. 191-4°, isomerized by heating 8 hrs. at 170-80° with a small amount of dilute HCl in a sealed tube to yield 61.5% Ia, m. 228.5-30.5° (from EtOH). Carefully neutralized solutions of the Na salts of I and Ia treated with an exactly equivalent quantity of aqueous AgNO3 and filtered, the precipitate carefully washed with H2O, alc., and Et2O, dried several days over P2O5 in vacuo, and screened to 100 mesh gave Ag salts (III, IIIa) suitable for reaction with Br. Reaction of III and IIIa with Br was carried out at various temperatures by the inverse addition procedure of Conly (C.A. 48, 2561b) in which the dry III or IIIa was added to Br in CCl4, in an apparatus in which the speed and extent of the reaction were followed by observation of the CO2 evolved. The products of the reaction were tabulated (Ag salt, temperature of reaction, % yield, m.p. IIa, n25D, and structure as shown by infrared spectrum given): III, 0-25°, 43, -4.8°, 1.5503, all trans; III, reflux, 47, -4.7°, 1.5505, all trans; IIIa, 0-25°, 48, -4.5°, 1.5507, all trans; IIIa, reflux, 37, -2.5°, 1.5510, all trans. To establish the stability to isomerization under the above exptl. conditions, known cis-1,2-dibromocyclohexane (II) and IIa were refluxed 12 hrs. with Br and AgBr. II, m. 10.0°, n25D 1.5512, was recovered with a 60% yield of material, m. 6.5°, n25D 1.5511, all cis; and IIa, m. -4.5°, n25D 1.5505, similarly yielded 94% material, m. -4.5°, n25D 1.5505, all trans. Although the data did not distinguish partial isomerization from complete retention of configuration a very large proportion of II survived the reaction. No isomerization of II took place on 12 hrs. refluxing with Br and AgBr in anhydrous CCl4. The mechanistic implications were discussed briefly.
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Reference:
Benzisoxazole – Wikipedia,
Benzisoxazole – an overview | ScienceDirect Topics