Raney nickel alkyl halides

In this context it is interesting to note that benzonitrile, Ph—C=N, trimerizes to a triazine on a Raney nickel surface. It was assumed that Jt-bonded nitriles were involved in the reaction mechanism.10 This reaction resembles the well-known template synthesis of phthalocyanine complexes from phthalodinitrile. Formation of linear polymers [—C(R)—N—] occurs on heating aryl or alkyl cyanides with metal halides.11... 

The synthesis uses alkylation by a benzylic halide and the reduction of both nitro groups is done catalytically with Raney nickel in the same step.6... 

All types of electrophiles have been used with 2-lithio-l,3-dithiane derivatives, including alkyl halides, sulfonates, sulfates, allylic alcohols, arene-metal complexes, epoxides, aziridines, carbonyl compounds, imines, Michael-acceptors, carbon dioxide, acyl chlorides, esters and lactones, amides, nitriles, isocyanates, disulfides and chlorotrialkylsilanes or stannanes. The final deprotection of the dithioacetal moiety can be carried out by means of different types of reagents in order to regenerate the carbonyl group by heavy metal coordination, alkylation and oxidation184 or it can be reduced to a methylene group with Raney-nickel, sodium or LiAIII4. 

Selenides are also nucleophilic and produce isolable selenonium salts (9) when treated with alkyl halides. They are easily oxidized to selenoxides (10) and further to selenones (11) under more forcing conditions (see Section 4). Reduction of selenides to the corresponding hydrocarbons is most conveniently achieved with nickel boride,or with tri-n-butyl- or triphenyltin hydride under radical conditions. " Other reagents for reductive deselenization include Raney nickel, lithium triethylborohydride, and lithium in ethylamine (Scheme 4). Benzylic selenides undergo radical extrusion reactions under thermal or photolytic conditions to produce... 

Raney nickel possesses remarkable hydrogenolysis ability, but the catalyst is readily deactivated by the halide ion released. Therefore, massive amounts of the catalyst are usually required to obtain satisfactory results. An example showing the reduction of a primary and a secondary alkyl chloride is shown in Scheme 3. ... 

The reagent reacts with alkyl halides, dialkyl sulfates and tosylates" to form the thiocyano derivatives, which can be desulfurized with Raney nickel." Potassium... 

The only example of an oxidative ring opening of the dihydrothiazine ring involves the ozonolysis of the derivative 172 to give compound 193. The 1—2 bond of dihydrothiazinones can be reductively cleaved in the presence of sodium in liquid ammonia. Thus compound 80a was converted into the salt 119 (Section V,B,4,a) although a stable isolable material, 119 readily underwent S-alkylation when treated with alkyl halides. Although Raney nickel is expected to effect the reductive desulfurization of dihydrothiazines, only one example of this reaction has been reported thus the compound 80b afforded N-acetylalanine ethyl ester. The 3—4 bond of dihydrothiazinones can be reductively cleaved under certain circum-... 

The PhS group may be removed in two ways reductively with Raney nickel to give 67, the product of y-alkylation of 65 with the alkyl halide, or oxidatively by thermal decomposition of the sulfoxide 68 (chapter 32) to give the new double bond in 69, the product of an extended aldol reaction, like the ester 30. 

Methyl-l,2,4-triazines 5 are obtained when 5-chloro-l,2,4-triazines are reacted with trimethylsulfoxonium halide and a base, followed by workup with deactivated Raney nickel.185 5-Alkyl-1,2,4-triazines 6 are obtained by reaction of 5-chloro-l,2,4-triazines with ethylidene-triphcnyl-/.5-phosphanes and aqueous workup.185... 

The hydrogenation of alkyl, aryl, or aralkylpyridinium salts is a moderately uncomplicated means of obtaining A-substituted piperidines. The quaternary salts reduce more readily than the salts of the parent pyridines (10) and yield of -substituted piperidines is usually better than obtained by reaction of the piperidine with the appropriate halide. The reduction may be carried out under a variety of conditions of pressure and temperature, in the presence or absence of base, in water, alcohol, or acetic acid. Raney nickel, palladium on a carrier, rhodium on a carrier and platinum oxide have all been used, with platinum oxide enjoying the widest use. 

In the presence of a Lewis acid, silyl enol ethers can be alkylated with reactive secondary halides, such as substituted benzyl halides, and with chloromethylphenyl sulfide (ClCH2SPh), an activated primary halide. Thus, reaction of the benzyl chloride 10 in the presence of zinc bromide with the trimethylsilyl enol ether derived from mesityl oxide allowed a short and efficient route to the sesquiterpene ( )-ar-turmerone (1.22). Reaction of ClCH2SPh with the trimethylsilyl enol ethers of lactones in the presence of zinc bromide, followed by 5-oxidation and pyrolytic ehmination of the resulting sulfoxide (see Section 2.2), provides a good route to the a-methylene lactone unit common in many cytotoxic sesquiterpenes (1.23). Desulfurization with Raney nickel, instead of oxidation and elimination, affords the a-methyl (or a-alkyl starting with RCH(Cl)SPh) derivatives. ... 

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