We describe herein the use of glycerol as an efficient and recyclable solvent for the addition of thiols to nonactivated alkenes. The catalyst-free reactions take place easily using glycerol at room temperature or heating and the corresponding linear thioethers were obtained in good to excellent yields. The method was used to synthesize new sulfur-containing eugenols, which were tested for their antioxidant activities. The semisynthetic thio-derivatives were more effective in inhibition of induced lipid peroxidation compared to the precursor eugenol and the synthetic antioxidant butylated hydroxyanisole.
PEG-400 and glycerin were successfully used as recyclable solvents for the synthesis of several alkenyl selenides and tellurides, in good yields and with high selectivity by the hydrochalcogenation of terminal alkynes. The nucleophilic species of selenium and tellurium were generated in situ from the reaction of the respective diphenyl dichalcogenide with NaBH 4 at 60 °C. This easy, general and improved method furnishes the corresponding alkenyl chalcogenides preferentially with Z configuration. The PEG-400 can be reused up to 4 times without previous treatment with comparable yields and selectivity.
Um método simples e eficiente foi desenvolvido para a hidrotiolação de fenilselenoalquinos utilizando KF/Al 2 O 3 em meio livre de solvente. O método é geral e permite a preparação seletiva de (Z)-1-fenilseleno-2-organotio-1-alquenos a partir de tióis aromáticos e alifáticos em rendimentos de razoáveis a bons. A presença do grupamento organosselênio direcionou a regioquímica da adição do tiol. O sistema catalítico pode ser reutilizado mais quatro vezes sem tratamento prévio.We present herein the results of a simple and efficient protocol for the hydrothiolation of phenylselenoalkynes promoted by KF/Al 2 O 3 using solvent-free conditions. This improved method furnishes selectively the corresponding (Z)-1-phenylseleno-2-organylthio-1-alkenes in reasonable to good yields starting from selenoalkynes and aliphatic or aromatic thiols. The presence of the phenylselenium group in the alkyne directed the regiochemistry of the thiol addition. The catalytic system can be reused up to 4 times without previous treatment.
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