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Using N-vinylimidazole as the reactant and introducing different ether-based side chains pH/salt dual-sensitive poly(imidazole ionic liquid) gel (P[CnOC2vim]Cl, n=1, 2, 3) was designed and synthesized. The structure characteristic of the gel was determined by IR spectra and SEM. The swelling ratio of gel under different conditions was investigated, including releasing property for ciprofloxacin (CIP) and berberine (Ber). The results showed that P[CnOC2vim]Cl(n=1, 2, 3) gel exhibits typical pH-sensitivity and salt-sensitivity. Its swelling ratio increased first and then decreased, and reached the maximum when the value of pH was 7.4; the swelling rate is smaller under the higher concentration of the NaCl. Furthermore, P[COC2vim]Cl gel with the short ether chain has the highest release rate of CIP and Ber at pH=7.4, the release behavior is in accord with the first-order kinetic equation. With the increase of the side chain of ether group, the cumulative release rate of P[CnOC2vim]Cl(n=2, 3) gel to CIP and Ber decreased obviously, and the behavior comforts to Higuchi kinetic equation. The results suggest that P[CnOC2vim]Cl(n=1, 2, 3) gel is the pH/salt dual-sensitive potential carrier for controlled drug release.

The DFT calculation of the B3LYP level was carried out to explore the reaction mechanism of the synthesis of spirocyclo[4, 5]decane skeleton by gold-catalyzed allenyl compounds. The more accurate energy under the CH3CN solvent in the experiment is calculated by the single point energy of the SMD model. Computational studies have shown that the reaction consists of three main steps: intramolecular cycloaddition of the end group carbon atoms of allenyl and vinyl groups, the semipinacol rearrangement process in which the four-membered ring is reconstructed into the five-membered ring, the elimination reaction releases the catalyst and obtains the product. The calculation results show that Zheng et al. reported that the gold-catalyzed synthesis reaction can easily occur under the experimental conditions due to its low activation free energy (12.42–16.79 kcal/mol). Furthermore, it was found that the MOMO(CH2)2 substituent has higher reactivity than the corresponding reactant of the phenyl substituent.