[12261-48-2] · C14H10Na · Sodium Anthracenide · (MW 201.23)
Solubility: sol THF, DME, HMPA.
Preparative Methods: a 0.1 M solution of the reagent in THF (or DME) is prepared by stirring sodium metal (1.0 equiv) and anthracene (1.1 equiv) in anhydrous solvent for 24 h under an argon atmosphere.2 The resulting solution exhibits the characteristic dark green color of the radical anion. The preparation time can be significantly reduced by ultrasound irradiation of the reaction.1,8
Handling, Storage, and Precautions: sodium anthracenide is both air- and moisture-sensitive. However, stock solutions of the reagent are stable for several weeks at rt when stored under an argon atmosphere. The reagent is flammable and should be handled with care. Excess reagent can be neutralized by the slow addition of isopropyl alcohol.
Sulfoximines unsubstituted at nitrogen are readily prepared by the titration of N-tosylsulfoximines with sodium anthracenide (eq 1).1 Alternative reagents employed to cleave the tosyl group (e.g. Sulfuric Acid, hυ, and Sodium-Ammonia) are less efficient (yields of 7-60% in eq 1).
Secondary arenesulfonamides are reductively cleaved by sodium anthracenide to provide the corresponding amines.2 N-Arenesulfonyl aziridines can be reduced to free aziridines without concomitant homolytic ring opening (eq 2).2c Primary arene- and methanesulfonamides are deprotonated, rather than reduced.
Sodium anthracenide converts arene mesylates to the corresponding phenols (eq 3).3 More powerful reducing agents such as Sodium Naphthalenide and Na/NH3 tend to produce competitive C-O bond cleavage.
Aromatic phosphate esters are reduced to the corresponding phenols upon treatment with sodium anthracenide (eq 4).4 Extensive C-O bond cleavage can occur with sodium naphthalenide or Na/NH3.
The a-naphthyldiphenylmethyl group is selectively cleaved by sodium anthracenide in the presence of the p-methoxytrityl protecting group (eq 5).5 No discrimination between the triarylmethyl ethers is observed with sodium naphthalenide. The order of reactivity is reversed for hydrolytic (aqueous acid) deprotection.
The dimesylates of vicinal diols are efficiently reduced to the corresponding alkenes upon treatment with sodium anthracenide (eq 6).6 In acyclic substrates, the product contains a mixture of alkene isomers.
The reductive cleavage of a cyclic ether to an alcohol with sodium anthracenide has been reported (eq 7). The enone moiety is undisturbed.7
Bryon A. Merrill
3M Pharmaceuticals, St. Paul, MN, USA