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.

中文翻译：

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4-羟基硫代香豆素的反应性研究：通过溶剂依赖性硫代克莱森重排合成稠合色噻吩和噻喃衍生物的新路线


4-羟基硫代香豆素 (1a-f) 的烷基化是在无水丙酮中，在室温下，使用 K ₂ CO ₃ (2 当量)，用各种烯丙基溴和炔丙基溴进行的。温度下，以良好的收率获得了相应的区域选择性S-烷基化产物4a-l和5a-n。然后，通过硫代克莱森重排，从相应的S-烯丙基醚(4a-l)和S-炔丙基醚(5a-n)合成各种新的硫杂环，得到环化产物7a-o和8a-n 产量良好。有趣的是，相应的 4-羟基硫代香豆素 (1a-f) 的 S-炔丙基醚根据溶剂提供了两种不同的产物。此外，各种 4-羟基硫代香豆素在硝基甲烷溶剂中，在 10 mol% p-TSA 催化剂存在下，在 80 °C 下与 2-methylbut-3-yn-2-ol (9) 直接反应，得到环化产物 10a-f 。 DFT计算是针对不同产物的形成进行的，并且进行了详细的阐述。该协议展示了几个显着的属性，包括良好到优异的产率、高度区域选择性的产物形成和高原子经济性。