Water-Dependent Selective Synthesis of Mono- or Bis-Selanyl Alkenes from Terminal Alkynes

We described here an alternative method for the selective synthesis of mono- or bis-selanyl alkenes. This method involves reactions of terminal alkynes with organylselenols, generated in situ by the reaction of diorganyl diselenides with H3PO2. These reactions proceeded efficiently at 90 °C under N2 atmosphere and are suitable to a range of diorganyl diselenides and terminal alkynes, both containing electron-withdrawing and electron-donating groups, affording the corresponding mono- or bis-selanyl alkenes in good yields and selectively. When the reactions were performed using 5.0 equiv. of H3PO2 (0.5 mL; 50 wt% in H2O), mono-selanyl alkenes were formed in good yields, whereas reactions carried out with additional H2O as the solvent (3.0 mL/mmol) provided bis-selanyl alkenes in high yields. Additionally, the solvent/reducing agent system (H2O/H3PO2) could be recovered and directly reused for further reactions to synthesize bis-selanyl alkenes.