[12095-50-5] · HNaSe · Sodium Hydrogen Selenide · (MW 102.96)
(nucleophilic agent for introduction of selenium by substitution reactions; mild reducing agent1)
Solubility: sol water, ethanol.
Form Supplied in: white crystals; very unstable in moist air.
Preparative Methods: reaction of Hydrogen Selenide with Sodium Ethoxide in anhydrous conditions under nitrogen.2 Aqueous or ethanolic solutions of NaHSe can be prepared by treatment of NaOEt, NaOH, or Na2CO3 solutions with H2Se.3 -5 The most convenient procedure involves reduction of Selenium with Sodium Borohydride.6 It allows the rapid and easy preparation of NaHSe without the necessity of generating dangerously toxic H2Se. A suspension of NaHSe in DMF is produced similarly.7
Handling, Storage, and Precautions: unstable compound; decomposes in moist air with the formation of polyselenides and precipitation of Se. It should be used directly as prepared in solution or suspension without isolation. Use in a fume hood.
NaHSe reacts with acyl chlorides to give diacyl diselenides after oxidation (eq 1).3 Aromatic aldehydes are converted into benzyl diselenides when treated with NaHSe in the presence of Piperidine hydrochloride followed by reduction with NaBH4.8
Selenoamides can be obtained from thioamides treated with NaHSe,9 whereas tetrasubstituted selenoureas are prepared by the reaction of NaHSe with methylthiouronium salts (eq 2).5 An efficient method for synthesis of selenoesters consists in transforming N,N-dimethylamides into N,N-dimethylimidoyl chlorides and treatment of these with NaHSe in ethanol (eq 3).10 Selenoformates are also prepared in this way.11 Carboxylic esters are easily cleaved into carboxylic acids and selenols by treatment with NaHSe in DMF or EtOH.7,12 Alkyl halides react with NaHSe to form selenides (eq 4)6 or selenols.13
NaHSe functions as an efficient agent for reductive elimination of vicinal dihalides. Chalcone dibromides undergo debromination when treated with NaHSe in boiling ethanol to give chalcones in 53-65% yield.14 NaHSe has been shown to be an effective reagent for reduction of alkyl, aryl, aralkyl, and functionally substituted disulfides to thiols under mild conditions in protic solvents.15
Jacek Mlochowski & Ludwik Syper
Technical University of Wroclaw, Poland