Aluminum amalgam ketones

Reductions with aluminum are carried out almost exclusively with aluminum amalgam. This is prepared by immersing strips of a thin aluminum foil in a 2% aqueous solution of mercuric chloride for 15-60 seconds, decanting the solution, rinsing the strips with absolute ethanol, then with ether, and cutting them with scissors into pieces of approximately 1 cm [141,142]. In aqueous and non-polar solvents aluminum amalgam reduces cumulative double bonds [143], ketones to pinacols [144], halogen compounds [145], nitro compounds [146, 147], azo compounds [148], azides [149], oximes [150] and quinones [151], and cleaves sulfones [141, 152, 153] and phenylhydrazones [154] (Procedure 30, p. 212). 

In addition to deoxygenation sulfoxides undergo reductive cleavage at the carbon-sulfur bond when heated in tetrahydrofuran with aluminum amalgam. Keto sulfoxides were thus converted to ketones in usually quantitative yields (the keto group remained intact) [141]. 

REDUCTION WITH ALUMINUM AMALGAM Reduction of Aliphatic-Aromatic Ketones to Pinacols [144]... 

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... 

It is also a strong base and an excellent reagent for the generation of ylides (Wittig and related reagents, for example). It reacts with esters to yield anions of p-ketosulfoxides. As the methylsulfinyl group of these compounds is easily removed by an aluminum amalgam, a useful synthesis of ketones is at hand. 

The oximes of 4,5,6,7-tetrahydrobenzo[6]thiophen-4-one and -7-one undergo the Beckmann rearrangement to give 146 354 451 and 147 (R = H),362 respectively. Compound 147 (R=C1) may be prepared similarly and by treating 2-chloro-4,5,6,7-tetrahydrobenzo[ ]thio-phen-7-one with ammonia in the presence of PPA.356 The oxime of 4,5,6,7 -tetrahydrobenzo [6]thiophene- 4-one affords 4-aminobenzo [6]-thiophene in a modified Leuckart reaction.241,355 The same oxime may be converted into 4-amino-4,5,6,7-tetrahydrobenzo[ ]thiophene by reduction with aluminum amalgam in methanol.452 The parent ketone also affords 4-amino-4,5,6,7-tetrahydrobenzo[6]thiophene on reaction with formamide at 165°, followed by acidic hydrolysis of the resulting 4-formylamino compound.355... 

Bissulfone 11 is reduced with aluminum amalgam to sulfone 32 lipimers are obtained at this stage, which are transformed into the common product 1 through subsequent oxidation to a ketone. 

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. 

The Julia olefin synthesis consists of the reaction of a sulfonyl anion with an aldehyde or ketone. The resulting alcohol is usually acetylated and the olefin formed by aluminum-amalgam reduction. The yield of / -hydroxysulfone is usually good, but the subsequent reductive elimination is more... 

Reductive elimination of (3-hydroxy sulfoximines with aluminum amalgam in acetic acid gives alkenes in good yields.70In one study, the resolved carbinol adducts of the ketone 93 and (+)-(S)-2b were individually treated with aluminum amalgam in acetic acid to give natural (-)-(3-panasinsene and its antipode in high enantiomeric purity.71... 

Certain aryl-substituted a- and /S-amino Intones have been successfully reduced to amino alcohols by catalytic hydrogenation over palladium, platinum, or nickel catalysts. Cleavage of the carbon chain sometimes occurs during catalytic hydrogenation of /S-amino ketones. Fair yields of the amino alcohols ate obtained in these cases by reduction with sodium amalgam in dilute acid or aluminum amalgam and water. /S-Amino aldehydes from the Mannich reaction (method 444) are reduced in excellent yields to amino alcohols by lithium aluminum hydride or by catalytic hydrogenation over Raney nickel. Lithium aluminum hydride reduces diazo ketones to 1-amino-2-alkanols (93-99%)- ... 

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. ... 

Finch has demonstrated that the sulfoximine approach is a viable alternative for fluoromethylenation (Scheme 12). The fluorosulfoximine (54) is deprotonated with LDA in THF and the aldehyde or ketone added to the anion. Conversion to the alkene is carried out with the standard aluminum amalgam procedure to yield a 1 1 mixture of ( )- and (Z)-alkenes (56). The reaction is very effective for aromatic and aliphatic aldehydes and aliphatic and alicyclic ketones, but, while aromatic and a,p-unsaturated ketones give good yiel of the addition adduct, the reductive elimination results in a variable amount of product formation. This method was tilled to the synthesis of prostaglandin 9-fluoromethylene (58 equation IS).- ... 

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