Facile pyridine-catalyzed phenylselenoetherification of alkenols

An innovative route for intramolecular cyclization of alkenols has been delineated through a ring closing reaction of suitably alkenols functionalized cyclic ethers tetrahydropyran or tetrahydrofuran type by reaction with phenylselenyl halides, in good yield. Proper choice of some Δ4- and Δ5-alkenols and pyridine as catalyst enables fast and facile cyclization. Catalytic amount of pyridine increased the yield, but in the presence of equimolar amount of pyridine, formation of corresponding cyclic ethers were quantitative and reaction were achieved instantaneously under extremely mild experimental conditions. It is possible that aromatic–aromatic ring stacking provides such role of pyridine. The effect of the steric hindrance in the starting alkenols, and halide ion of the selenenylating reagent is not significant, all halides generally giving equal results, and primary, secondary, tertiary and more substituted alkenols also giving quantitative yields.

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