The alkylation of 4-hydroxythiocoumarins (1a-f) was carried out with various allyl bromides as well as propargyl bromides using K2CO3 (2 equiv.) in anhydrous acetone at room temperature, and the corresponding regioselective S-alkylated products 4a-l and 5a-n were obtained in good yields. Then, the synthesis of a variety of new sulfur heterocycles is accomplished by employing thio-Claisen rearrangement from the corresponding S-allyl ethers (4a-l) and S-propargyl ethers (5a-n) to provide the cyclised products 7a-o and 8a-n in good yields. Interestingly, the S-propargyl ethers of the corresponding 4-hydroxythiocoumarins (1a-f) provided two different products depending on the solvent. Furthermore, various 4-hydroxythiocoumarins provided the cyclised products 10a-f directly on reaction with 2-methylbut-3-yn-2-ol (9) in the presence of 10 mol% p-TSA as catalyst in nitromethane solvent at 80 °C. The DFT calculations are done for the formation of different products, and it has been elaborated. The protocols demonstrate several notable attributes, including good to excellent yield, highly regioselective product formation, and high atom economy.

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