Pyridylseleno group in organic synthesis. Part 4. Oxyseleniation of olefins using pyridine-2-selenenyl bromide as a selenium reagent and its utilization in the synthesis of 2-pyridyl vinylic selenides

Abstract

The reaction of olefins with pyridine-2-selenenyl bromide in methanol as solvent affords β-methoxyalkyl 2-pyridyl selenides (A) in good to excellent yields. This reaction also proceeds in acetic acid and aqueous tetrahydrofuran to give acetoxyseleniated and hydroxyseleniated products respectively. Oxidative elimination of (A) proceeds at room temperature, even in the case where the 2-pyridylseleno group is located at a terminal carbon, to afford methyl vinylic ethers in good yield. Treatment of (A) with lithium di-isopropylamide produces 2-pyridyl vinylic selenides (B). Deprotonation of (B) can be carried out under milder conditions than those of the corresponding phenyl vinylic selenides.