The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Stereochemical investigations of 1,4-substituted cyclohexane derivatives. 4-Hydroxy- and 4-aminocyclohexane-1-carboxylic acid and their esters; and 4-hydroxy-1-hydroxymethylcyclohexane》. Authors are Schneider, Woldemar; Huettermann, A..The article about the compound:cis-4-Aminocyclohexane carboxylic acidcas:3685-23-2,SMILESS:N[C@H]1CC[C@H](CC1)C(O)=O).Quality Control of cis-4-Aminocyclohexane carboxylic acid. Through the article, more information about this compound (cas:3685-23-2) is conveyed.
Malonic ester synthesis with ethyl β-chloropropionate, followed by ring closure of the product obtained gave 4-hydroxy-1-cyclohexanone (I). Hydrogenation of I (Raney-Ni, atm. pressure, room temperature) in alk. medium gave cis-4-hydroxycyclohexane-1-carboxylic acid (cis-II), m. 152°; Et ester, (cis-III) b12 130°. Hydrogenation of ethyl 4-hydroxybenzoic acid (Raney-Ni, 150 atm., 150°) gave trans-III, b13 139-140°, saponification of which gave the trans-II, m. 119.5°. Reduction of trans-III with Na-EtOH or LiAlH4, gave a cis-trans mixture of 4-hydroxy-1-hydroxymethylcyclohexane (IV), from which the trans isomer (V) was separated, m. 104°; the cis isomer (VI) was recovered by distillation from the residue. Hydrogenation of ethyl 4-aminobenzoic acid (Ru-C, 110 atm., 80°) gave a cis-trans mixture of 4-amino-1-carbethoxycyclohexane (VII), which was separated by distillation, giving cis-VII and trans-VII. The exptl. determined dipole moments (μ in Debye units) of these compounds are: cis-II 2.10 ± 0.1, trans-II 246 ± 0.002, cis-III 2.86 ± 0.03, trans-III 2.56 ± 0.04, VI 2.29 ± 0.02, V 2.60 ± 0.1, cis-VII 2.60 ± 0.01, and trans-VII 2.44 ± 0.02.
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Reference:
Synthesis and Crystal Structure of a Chiral C3-Symmetric Oxygen Tripodal Ligand and Its Applications to Asymmetric Catalysis,
Chiral lanthanide(III) complexes of sulphur–nitrogen–oxygen ligand derived from aminothiourea and sodium D-camphor-β-sulfonate