The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Application of the cyano ester ring closure to five- and six-membered rings》. Authors are Fuson, Reynold C.; Cole, Wayne.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).COA of Formula: C8H12O4. Through the article, more information about this compound (cas:610-09-3) is conveyed.
cf. F. and Kao, C. A. 23, 2424. Et α,α’-dibromopimelate and KCN in absolute EtOH, refluxed for 60 hrs., give 80-8% of Et 1-cyano-1,2-cyclopentanedicarboxylate, b2 126-8°, d420 1.108, nD20 1.4560; hydrolysis with concentrated HCl gives a mixture of trans- and cis-1,2-cyclopentanedicarboxylic acid (Perkins, J. Chem. Soc. 65, 572(1894)). Similarly Et α,α’-dibromosuberate yields 48-55% of Et 1-cyano-1,2-cyclohexanedicarboxylate, b2 129-30°, d420 1.082, nD20 1.4570; hydrolysis with 20% HCl yields a mixture of the 2 1,2-cyclohexanedicarboxylic acids, the trans-isomer being obtained pure (Baeyer, Ann. 258, 213(1890)). Et α,α’-dibromoazelate and Et α,α’-dibromosebacate failed to give detectable quantities of the cyclic CN esters containing 7- or 8-membered rings.
In addition to the literature in the link below, there is a lot of literature about this compound(cis-Cyclohexane-1,2-dicarboxylic acid)COA of Formula: C8H12O4, illustrating the importance and wide applicability of this compound(610-09-3).
Reference:
Benzisoxazole – Wikipedia,
Benzisoxazole – an overview | ScienceDirect Topics