Abstract
Sulfated tin oxide (STO) has been found to be an efficient reusable solid superacid catalyst for C3-alkylation and O-alkylation of 4-hydroxycoumarins with benzylic, allylic alcohols/and corresponding acetates respectively, in acetic acid under reflux conditions with good yield of products.
Highlights
Coumarin is a privileged scaffold among heterocyclic and are known to possess a wide range of biological activities including antibiotic, anti-malarial, antifungal, antiviral, and cytotoxic [1,2,3,4,5,6,7,8]
In continuation of our interest in developing novel synthetic methodologies, carbon-carbon, carbonheteroatom bond formations [51,52,53,54,55,56,57], here in we report our brief findings for a highly efficient method for the C-C bond and C-O bond formation via Sulfated tin oxide (STO) catalyzed C3-alkylation and O-alkylation reactions of 4-hydroxycoumarins with 20 benzylic alchols and benzyl O-acetates, respectively
We found that a remarkable solvent effect, as acetic acid proved to be the suitable solvent for obtaining good yields under reflux conditions for 5 h (Table 1, entry 6)
Summary
Coumarin is a privileged scaffold among heterocyclic and are known to possess a wide range of biological activities including antibiotic, anti-malarial, antifungal, antiviral, and cytotoxic [1,2,3,4,5,6,7,8]. Processes involving conventional acids, are inherently associated with problems such as high toxicity, corrosion, catalyst waste and difficulty in separation and recovery. Some of these catalytic systems have several limitations such as longer reaction times, lack of reusability, poor yields, as well. In continuation of our interest in developing novel synthetic methodologies, carbon-carbon, carbonheteroatom bond formations [51,52,53,54,55,56,57], here in we report our brief findings for a highly efficient method for the C-C bond and C-O bond formation via STO catalyzed C3-alkylation and O-alkylation reactions of 4-hydroxycoumarins with 20 benzylic alchols and benzyl O-acetates, respectively
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