A reaction has been developed to synthesize a series of tetrahydro-2H-selenopyran derivatives from benzalace-tones,sodium borohydride,and elemental selenium by one-pot method.The reaction proceeds well to construct a tetrahy-dro-2H-selenopyran ring and six new bonds.Twenty tetrahydro-2H-selenopyran derivatives were obtained,and the yield was up to 91％.The X-ray single crystal analysis showed that this selenium-containing heterocyclic ring exists as a stable chair conformation similar to cyclohexane.The reaction works well when scaled up to the gram scale.A possible mechanism was proposed,involving hydrogenation of selenium/double Michael addition/cleavage of diselenide bond/Michael addition/Aldol reaction.This reaction is characterized by high compatibility to substrates,transition-metal free,and mild reaction conditions.
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