Sodium amalgam desulfurization

The aldol adducts 17 can be transformed by desulfurization with sodium amalgam to the substituted dihydroisoxazoles 20, or directly to /f/T-dihydroxy ketones by hydrogenolysis24. In general, chromatographic separation of the sulfmyldihydroisoxazoles 17 and/or their desulfurization products is possible and allows isolation of the enantio- and diastereomerically pure compounds24. 

The diastereomeric lactones could be separated by chromatography and converted into optically active lactones by desulfurization with sodium amalgam or by pyrolysis to the corresponding butenolides. 

Desulfurization of fl, a-epoxy sulfones 239 prepared from allylic sulfones 238 and m-chloroperbenzoic acid with sodium amalgam leads to the formation of allyl alcohols (240) in good yields (equation 144)138. Allyl alcohols prepared by this method are listed in Table 16. 

Harmata and co-workers introduced a procedure for the reductive desulfurization of selected 2,1-benzothiazines with sodium amalgam, leading to the formation of the 2-alkylanilines in high yields <94S142>. This method is regioselective and general. As an example, alkylation of 187 followed by treatment with Na/Hg resulted in the formation of the aniline 188 in 68% overall yield (Scheme 50). 

DESULFONYLATION Lithium-Ethylamine. Sodium-Ethanol. Sodium amalgam. Tetrakis(tnphenylphosphine)palladium. DESULFURATION ... 

Sodium amalgam [Na(Hg)] used in excess in alcohols, is well known to desulfurize sulfides, sulfoxides, and, above all, sulfones, but a number of side reactions can occur. It was found that... 

Cyclopropyl sulfones 3 are easily reduced to cyclopropanes 4 by treatment with sodium amalgam in refluxing ethanol. Yields above 80% have been reported.However, quite different reaction conditions are required to perform reductive desulfurization of cyclopropanesulfinic acids 5, i.e. the use of mercury(II) chloride, concentrated hydrochloric acid, and heat ethylmagnesium bromide followed by acid has also been used but yields were poor. ... 

Lithiation. MeLi is successfully added to carbonyl or ester groups <84JOC4595>. Lithiated isoxazoline (169) from (168) with ( S)-methyltoluene-p-sulfinate afforded a mixture of the two diastereo-meric isoxazolines (170) and (171). They can be easily separated by chromatography. Desulfurization of individual isomers was achieved by sodium amalgam, providing the pure enantiomers (172) and (173) (Scheme 25) <84CC55l>. 

Desulfurization can be achieved by sodium amalgam reduction, producing the unsaturated hydrocarbons, e.g., bicyclo[2.2.2]oct-2-ene (19) in 83% yield51. 

Alkane-2,5-dione Synthesis. On treatment with n-BuLi and an acyl chloride, (1) affords an a-acylated product, which easily undergoes reductive desulfurization with aluminum amalgam or sodium amalgam. Deprotection forms an alkane-2,5-dione (eq 3). - ... 

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