Benzyl halides reaction with potassium

Lithium dialkylamides of hindered amines can generate aryl-substituted car-benes from benzyl halides. Reaction of a,a-dichlorotoluene or a,a-dibromotoluene with potassium t-butoxide in the presence of 18-crown-6 generates the corresponding a-halophenylcarbene. The relative reactivity data for carbenes generated under these latter conditions suggest that they are free. The potassium cation would be expected to be strongly solvated by the crown ether and is evidently not involved in the carbene-generating step. 

For example, direct treatment of red phosphorus with potassium hydroxide in a mixture of dioxane and water with a phase-transfer catalyst (benzyltriethylammonium chloride) allows direct reaction with primary haloalkanes to form the trialkylphosphine oxide in moderate (60-65%) yield.1415 Allylic and benzylic halides are similarly reported to generate the corresponding tertiary phosphine oxides. When the reaction is performed with a,(o-dihalides, cyclic products are generated only with four- and five-carbon chains the third site... 

The data for the reactions of potassium cyanide with benzyl halides at 85 C and 25 C are summarized in Tables I-III and graphical representations of these data are shown in Figures 1-3. The reactions carried out at 85 C were followed to 70% completion, while those at 25 C were followed to 50% completion. In general, excellent first-order kinetic plots were obtained. Each point on the graphs represents an average of at least three kinetic determinations. It is interesting to note that in the absence of added water (solid-liquid phase transfer catalysis), the rates of benzyl halide disappearance were more accurately described by zero-order kinetics. 

The results from our work on the reaction of propylene oxide with cobalt carbonyl and base in methanol are given in Table VIII. Several base/metal oxide combinations were evaluated under mild reaction conditions. The difference in activity between the bases was not as pronounced as that observed in the reaction with benzyl halides with the exception of potassium methoxide which, when used alone, gave exclusively the hydroxy ether resulting from methoxide addition to the epoxide ring. However, the activity of sodium... 

Alkylation of Alkali Metal Cyanides by Alkyl Halides Activated in the a-Posi-tion by a Double Bond. When a mixture consisting of 4 to 8 moles of an alkyl halide activated in the apposition by a double bond is heated with 1 mole of alkali metal ferrocyanide, several alkylation products of the ferrocyanide anion can be isolated from the reaction mixture (12). The relative proportions of the tetra-, penta-, and hexaalkylated complexes can be varied by varying the alkyl halide to ferrocyanide ratio and the time of reaction. When potassium ferrocyanide is alkylated with benzyl bromide at a ratio of 4 alkyl halides to ferrocyanide anion, short reaction times favor the tetraalkylated complex an 8 to 1 ratio and long reaction times favor the hexaalkylated complex of the alkylating agents tested benzyl bromide provided the fastest alkylation ... 

Fluoride chloride exchange of 1 -chlorooctane (3) with potassium fluoride, catalyzed by tetra-butylammonium bromide gives higher yields (72%) of 1-fluorooctane (4) in the presence of formamide than those reactions conducted in the presence of water.57 In the case of 1-bro-mooctane, benzyl chloride or phenethyl chloride, fluoride halide exchange gives only a yield of < 50%. 

Reaction with ethanolic potassium hydroxide. Boil 0.5 ml of the compound with 4 ml of 0.5 m ethanolic potassium hydroxide under reflux for 15 minutes. Most alkyl halides and benzyl halides give a crystalline precipitate of the potassium halide. Dilute with 5 ml of water, acidify with dilute nitric acid and test with silver nitrate solution. 

The Finkelstein procedure169 exploits the solubility differences between halide salts (e.g. Nal and NaCl in acetone170) to effect the conversion of alkyl chlorides to alkyl iodides. Ferric chloride has been used as catalyst in Finkelstein reaction of tertiary alkyl and benzyl chlorides and sodium iodide in nonpolar solvents171. Cu(I) iodide, combined with potassium iodide in HMPA, is used for the synthesis of gem-diiodoolefins from the corresponding gem-dibromides172. 

Potassium tellurocyanate, prepared from potassium cyanide and tellurium in DMSO, reacts with benzyl halides to produce benzyl tellurium cyanides in good yields. Because of the sensitivity of potassium tellurocyanate to oxygen and of some of the benzyl tellurium cyanides to light, the reactions must be carried out in an inert atmosphere (nitrogen or argon) under red light. 

The synthesis of benzyl fluorides from benzyl halides is problematic due to the tendency to undergo Friedel Crafts reactions.The fluorination of benzyl bromide with thallium(l) fluoride gives impure benzyl fluoride and attempts to fluorinate benzyl halides with anti-mony(III) fluoride, silver fluoride, and potassium fluoride were all unsuccessful. Benzyl fluorides with substituents which deactivate the aromatic system towards Friedel-Crafts reactions are successfully obtained through halogen exchange with mercury(II) fluoride (Table... 

The transformation of alkyl halides with cyanides (equation 1) represents not only the classical route to nitriles, but, if modified properly, is still of very great practical importance even today. A whole series of review articles stress the scope and value of this reaction. Although the substituent R may be varied to a large extent, the primary as well as the benzylic halides generally give higher yields than secondary and tertiary ones, as, with the latter, the formation of alkenes gains in importance. This side reaction as well as the undesired formation of alcohols and ethers, which sometimes takes place in aqueous media or with alcohols as solvent, is of course due to the basicity of the cyanide ion. Under deleterious conditions one may even observe carboxylic acids, which result fi-om the hydrolysis of the nitriles. - Some of these undesired side reactions may be avoided by the use of CuCN instead of sodium or potassium cyanide. ... 

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