Aluminum amalgam desulfurization

Thione or alkylthio groups have also been involved in nucleophilic substitutions with hydrazine, or amines, and by desulfurization using Raney nickel or aluminum amalgam. 

Asymmetric synthesis of fi-hydroxy carboxylic estersEsters of 1 in the presence of f-butylmagnesium bromide as base react with aldehydes and ketones to form optically active a-sulfinyl-jS-hydroxy carboxylic esters, which are desulfurized by aluminum amalgam in aqueous THF (equation I). Chemical yields are 75% of... 

As outlined by Roush and Walts,62 sulfoxide 21 was converted to the corresponding dianion with lithium diisopropylamide (LDA) and alkylated with n-butyl iodide to provide a diastereomerically complex mixture that was then converted directly to 2-butyl-3R-methylcyclohex-2-en-l-one (50% yield, 6 1 (P oc) mixture at C-2) upon thermolysis. We found that sulfoxide 21 could be alkylated with 2-(2-bro-moethyl)-2,5,5-trimethyl-1,3-dioxane63 and that the resultant complex mixture could be desulfurized with aluminum amalgam to furnish desired ketone 17 in 40-50% yield as 9 1 (P a) mixture at C-2. Surprisingly, alkylation of this sulfoxide dianion was not improved using 2-(2-iodoethyl)-2,5,5-trimethyl-l,3-dioxane17 in place of the bromide. 

Reductive desulfurization of 9-(phenylsulfonyl)furo[2,3- ]quinoline and its 2-methyl derivative can be effected by treatment with LAH in THF solution at reflux, but proceeded poorly with aluminum amalgam, the reagent of choice for the reductive cleavage of vinyl sulfones <83JOC774>. Raney nickel was used to remove a thiomethyl substituent from the central ring of a furochromone direct precursor to visnagan <89JOC448l>. 

Aldol-Type Addition. Aldol-type addition of the magnesium enolate of (R)-(+)-7-butyl 2-(p-tolylsulfinyl)acetate, prepared with 7-butylmagnesium bromide, with aldehydes and ketones afforded, after desulfurization with Aluminum Amalgam, p-hydroxy esters in very high diastereoselectivity (eq Two chiral centers are created in the first step with very high diastereoselectivity (mainly one diastereomer is formed). A model M based on the structure of the sulfinyl ester enolate (determined by C NMR) and on electrophilic assistance of magnesium to the carbonyl approach, was proposed to explain and predict the absolute configuration of the two created chiral centers. ... 

Aldol-Type Condensation. The aldol-type condensation of the enolate anion of sulfinylpropionate, which was prepared as usual with the base t-butylmagnesium bromide, with aldehydes afforded after desulfurization with Aluminum Amalgam the corresponding 3-hydroxy esters in high yield (90%) and, with aliphatic aldehydes, high diastereoselectivity (eq 3). The amount of asymmetric induction was determined by transformation of the 3-hydroxy esters to the corresponding isopropyl-substituted alcohols. 

Vinylic sulfoxide (30) is desulfurized to (31) with f-butyllithium (equation 80), and sulfone (32) affords triphenylethylene on reduction with aluminum amalgam or lithium aluminum hydride (equation 81). ... 

Desu uriz0iott. In an investigation of the structure of the antibiotic gliotoxin (1), Johnson et a . were able to effect desulfurization to desthiogliotoxin (2) with aluminum amalgam in neutral alcoholic solution use of Raney nickel led to over-reduction. 

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). - ... 

Sulfanylpyrido[2,3-t/]pyridazin-5(6/7)-one is desulfurized by amalgamated aluminum in 50% ethanol at reflux temperature to give a low yield of 7,8-dihydropyrido[2,3-rf]pyridazin-5(6//)-one (6).76... 

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