New 6-butylamino-6-deoxycellulose and 6-deoxy-6-pyridiniumcellulose derivatives with highest regioselectivity and completeness of reaction

This paper investigates the nucleophilic substitution (SN) reactions of tosylcellulose with butylamine and pyridine, respectively. The SN reactions of tosylcellulose 1 (DSTotal 2.02; DSC-6 1.0) with butylamine carried out at 25, 50, 75 and 100 °C in both dimethyl sulfoxide (DMSO) and pure butylamine showed that the regioselectivity of substitution at C-6 of cellulose is temperature dependent: the highest regioselectivity at C-6 can be reached at 25 and 50 °C; substitution at C-2 also occurred at 75 and 100 °C. The substitution speed in pure butylamine is greater than that in the presence of DMSO. A complete and regioselective substitution at C-6 with a DS of 1.0 was obtained under the conditions of 50 °C, 40 h in butylamine. The substitution reactions of 1 with pyridine carried out at 25, 50, 75 and 100 °C for 24 h in DMSO did not occur. In contrast to this the SN reactions done in pure pyridine showed that a temperature- and steric-dependent, regioselective substitution took place at C-6 at temperatures from 25 to 145 °C. The highest regioselectivity and completeness at C-6 can be obtained at 100 °C for 90 h, whereas at 145 °C substitution also occurs at C-2. The results were proved by 1H NMR and 13C NMR spectroscopy.

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