Synthesis of alkenyl selenides and tellurides using PEG-400

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 NaBH4 at 60 degrees 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.