Amalgam procedure

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).- ... 

Unforiunalely. this approach does not work for substituted I, I-dibromides wilh the notable exception of the irimcthylxilyl substituent the mono-and disubstitulcd derivatives 13b [19] and 13c 20. respectively, were prepared in comparable yields. In the ease of 13c, it is not necessary to use the tedious amalgam procedure as the reaction proceeds in the normal way wilh magnesium in diethyl ether (Scheme 11.5) pure crystalline 13c can he isolated in 359 yield on concentrating and cooling the reaction mixture [20. ... 

According to Winslow, Liebhafsky and Smith, pure RbOH and CsOH are prepared by electrolysis of the chlorides, using an amalgam procedure carried out in a multicell apparatus. 

Aliphatic hydrocarbons can be prepared by the reduction of the readily accessible ketones with amalgamated zinc and concentrated hydrochloric acid (Clemmensen method of reduction). This procedure is particularly valuable for the prep>aration of hydrocarbons wdth an odd number of carbon atoms where the Wurtz reaction cannot be applied with the higher hydrocarbons some secondary alcohol is produced, which must be removed by repeated distillation from sodium. 

Other halogen carriers may be used, e.g., 1-2 g. of iron filings, or 1 g. of aluminium amalgam. The bromine must then be added slowly from a dropping funnel to the benzene warmed on a water bath the apparatu.s shown in Fig. II, 13, 9 is suitable and a trap for the hydrogen bromide must, however, be inserted into the top of the condenser. After all the bromine has been introduced, the mixture is heated on a water bath until no red vapours are visible above the liquid. The Subsequent procedure is as above. 

METHOD 2 By far the most popular method currently available. This is a really convenient way to convert P2P or MD-P2P into meth and MDMA ( ecstacy ). It is a very clean procedure, akin to that of the NaBHgCN method, using amalgamated aluminum catalyst made from ordinary household foil [26, 28]. When Strike was reading all the underground literature on the use of household... 

Titanium Sulfates. Solutions of titanous sulfate [10343-61-0] ate readily made by reduction of titanium(IV) sulfate ia sulfuric acid solutioa by electrolytic or chemical means, eg, by reduction with ziac, ziac amalgam, or chromium (IT) chloride. The reaction is the basis of the most used titrimetric procedure for the determination of titanium. Titanous sulfate solutions are violet and, unless protected, can slowly oxidize ia coatact with the atmosphere. If all the titanium has been reduced to the trivalent form and the solution is then evaporated, crystals of an acid sulfate 3 Ti2(S0 2 [10343-61-0] ate produced. This purple salt, stable ia air at aormal temperatures, dissolves ia water to give a stable violet solutioa. Whea heated ia air, it decomposes to Ti02, water, sulfuric acid, and sulfur dioxide. 

The present procedure was developed from those of Wallach and Freylon, based upon the general method discovered by Leuckart. a-Phenylethylamine also can be prepared satisfactorily by the reduction of acetophenone oxime with sodium and absolute alcohol or sodium amalgam, but the reagents are more expensive and the processes less convenient. The amine has been obtained by reducing acetophenone oxime electro-lytically, by reducing acetophenone phenylhydrazone with sodium amalgam and acetic acid, from a-phenylethyl bromide and hexamethylenetetramine, and by the action of methyl-magnesium iodide upon hydrobenzamide, as well as by other methods of no preparative value. 

This procedure is an adaption of one described by Hauser and Chambers. Previous preparations include the benzylation of diethyl phenylmalonate followed by hydrolysis, the benzylation of phenylacetonitrile followed by hydrolysis, the benzylation of phenylacetic acid through the Ivanov reagent, and the reduction of oi-phenylcinnamic acid using sodium amalgam. ... 

Benzyne can also be generated from o-dihaloaromatics. Reaction of lithium amalgam or magnesium results in formation of a transient organometallic compound that decomposes with elimination of lithium halide. l-Bromo-2-fluorobenzene is the usual starting material in this procedure. 

Although as already stated the use of metal amalgams, and in particular use of the Jones reductor or of the related silver reductor, is the best method of reducing solutions in preparation for titration with an oxidant, it may happen that for occasional use there is no Jones reductor available, and a simpler procedure will commend itself. In practical terms, the need is most likely to arise in connection with the determination of iron, for which the reduction of iron(III) to iron(II) may be necessary. 

Trost published a desulphonylation procedure for aryl alkyl sulphones using an excess of sodium amalgam in buffered ethanol126 (equation 52). Trost claimed that this is superior to earlier reactions using sodium amalgam in ethanol because of a couple of factors the use of the acid phosphate buffer to prevent formation of significant amounts of sodium methoxide is particularly important, since this can cause isomerizations in base-sensitive substrates, and the temperature should be kept low, but optimized for each substrate. 

Pioneering work on the desulphonylation of jS-ketosulphones was carried out by Corey and Chaykovsky - . This reaction was part of a sequence which could be used in the synthesis of ketones, as shown in equation (53). The main thrust of this work was in the use of sulphoxides, but Corey did stress the merits of both sulphones and sulphonamides for different applications of this type of reaction. The method soon found application by Stetter and Hesse for the synthesis of 3-methyl-2,4-dioxa-adamantane , and by House and Larson in an ingenious synthesis of intermediates directed towards the gibberellin skeleton, and also for more standard applications . Other applications of the method have also been madealthough it does suffer from certain limitations in that further alkylation of an a-alkyl- -ketosulphone is a very sluggish, inefficient process. Kurth and O Brien have proposed an alternative, one-pot sequence of reactions (equation 54), carried out at — 78 to — 50°, with yields better than 50%. The major difference between the two routes is that the one-pot process uses the desulphonylation step to generate the enolate anion, whereas in the Corey-House procedure, the desulphonylation with aluminium amalgam is a separate, non-productive step. 

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