tailieunhanh - Preparation of some new benzo[d]thiazole derivatives

In this work, four new benzo[d]thiazole derivatives were synthesized successfully from vanillin. Nitration of vanillin gave nitrovanillin followed by cyclization reaction with o-aminothiophenol under microwave irradiation in 4 minutes to give nitroaromatic compound 3. The reduction to convert the nitro group to amino group was optimized. It was found that Fe/ con. HCl in ethanol was the best condition for this case about both yield ( 95 %) and simple procedure to give compound 4 as a salt. | Vietnam Journal of Chemistry, International Edition, 55(4): 433-437, 2017 DOI: Preparation of some new benzo[d]thiazole derivatives Duong Quoc Hoan1*, Vu Thi Anh Tuyet2, Le Thanh Duong1, Nguyen Hien1 1 Department of chemistry, Hanoi National University of Education 2 Department of science, Lang Son College of Education Received 9 February 2017; Accepted for publication 28 August 2017 Abstract In this work, four new benzo[d]thiazole derivatives were synthesized successfully from vanillin. Nitration of vanillin gave nitrovanillin followed by cyclization reaction with o-aminothiophenol under microwave irradiation in 4 minutes to give nitroaromatic compound 3. The reduction to convert the nitro group to amino group was optimized. It was found that Fe/ con. HCl in ethanol was the best condition for this case about both yield ( 95 %) and simple procedure to give compound 4 as a salt. Acetylation occurs at both phenolic hydroxyl group and amino group of the salt 4 to form N,O-acetyl compound 5. Under mild hydrolysis 5 produces N-acetyl compound 6. The structures of these compounds were established by IR, 1H and 13C NMR and mass spectral analyses. Keywords. Benzo[d]thiazole, vanillin, reduction, microwave. 1. INTRODUCTION [7]. In 2013, J. Pan et al. showed that complexes D of Re metal containing benzo[d]thiazole with various substituent Rs exhibited the lipophilicities in range logPC18 = 1-4, their binding affinities (Ki = 30617 nM) to A 1-40 fibrils. Nitroaromatic compounds play an essential role not only in organic synthesis but also in human life. For instance, they are pesticides, bacterial degradation, etc. [8]. Therefore, in this work, benzo[d]thiazole derivatives E were designed by retaining the structure of vanillin and connecting with a benzo[d]thiazole ring synthesized from vanillin, figure 1. To take advantages of amino, amide and nitroaromatic compounds, R1 is either NO2 group, an amino group or an acetamido groups. R2 is an