Regioselectivity in the glycosylation of 5-(3-chlorobenzo[b]thien-2-yl)-4H-1,2,4-triazole-3-thiol |
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Authors: | El Sayed H El Ashry Ahmed A Kassem Hamida M Abdel-Hamid Farida Louis Mohamed R Aouad |
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Institution: | a Chemistry Department, Faculty of Science, Alexandria University, Alexandria, Egypt b Chemistry Department, Faculty of Science, University of Science and Technology-Mohamed Boudiaf-USTO-MB BP:1505 ELM’NOUAR, ORAN 31000, Algeria |
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Abstract: | The glycosylation of 5-(3-chlorobenzob]thien-2-yl)-4H-1,2,4-triazole-3-thiol (1) and its 3-benzylsulfanyl and 3-methylsulfanyl derivatives with different glycosyl halides 2-4 has been studied in presence of base. The S-glycosides 5-7 were obtained in the presence of triethylamine, whereas the respective S,N4-bis(glycosyl) derivatives 8-10 were synthesized in the presence of potassium carbonate; the S,N2-bis(glycosyl) isomer 11 could also be isolated in the case of the galactosyl analog. Similarly, after protecting 1 as 3-benzyl(methyl)sulfanyl derivatives 12 or 13, the N4-glycosyl analogs 14-19 as well as minor amounts of S,N2-bis(galactosyl) isomers 20 and 21 were formed. The theoretical calculations using AM1 semiempirical methods agreed with the experimental results. Microwave irradiation (MWI) led to higher yields in much less time than the conventional methods, and no change in regioselectivity has been noticed. |
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Keywords: | Thioglycoside Selective glycosylation Glycosyl halide Benzo[b]thiophene 1 2 4-Triazole Microwave irradiation |
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