Reactions with Reactive Halides

Reaction of 2-methylpyridine iV-oxide with p-toluenesulfonyl chloride or phosphorus oxychloride gives 2-pyridylmethyl chloride (Scheme 47), and related reactions with reactive halides have also been studied (62JOC3856, 81JHC939). 

Allylic zinc reagents undergo cross-coupling reactions with reactive halides leading to 1,5-dienes. Usually the new carbon-carbon bond is formed from the more-substituted end of the allylic system (Scheme 9-11) [30]. 

Alkylation of arenesulfinate salts is a very general reaction for the preparation of alkyl sulfones. Reaction conditions utilizing alcoholic or dipolar aprotic solvents are t) ical, but phase-transfer conditions have been described. Reaction with reactive halides is generally facile (eq 1) triflates have likewise been displaced with ease by p-toluenesulfinate. ... 

Reaction with hydrogen halides (Sec tion 4 7) The order of alcohol reactiv ity parallels the order of carbocation staiiility RjC" > R2CH > RCHj" > CHj" Benzylic alcohols react readily... 

The anion of DMSO undergoes a phenylation reaction with aryl halides under sunlight stimulation38. The presence of benzhydryl methyl sulfoxide (maximum yield 5%) in all runs, the sunlight activation, the order of reactivity of halobenzenes (I > Br > Cl), the inhibition of the reaction with oxygen, all hint at the SRN139-44 mechanism (Scheme 3). 

Horton, H. R. Koshland, D. E. Jr. Reaction with reactive alkyl halides. Methods Enzymol. 1967, 11, 556-565. 

In absence of diluent or other effective control of reaction rate, the sulfoxide reacts violently or explosively with the following acetyl chloride, benzenesul-fonyl chloride, cyanuric chloride, phosphorus trichloride, phosphoryl chloride, tetrachlorosilane, sulfur dichloride, disulfur dichloride, sulfuryl chloride or thionyl chloride [1], These violent reactions are explained in terms of exothermic polymerisation of formaldehyde produced under a variety of conditions by interaction of the sulfoxide with reactive halides, acidic or basic reagents [2], Oxalyl chloride reacts explosively with DMSO at ambient temperature, but controllably in dichloromethane at -60°C [3]. 

Several methods for the preparation of the parent compound in this system, tris(trimethylsilyl)phosphite, have been reported.114 118 The application of this and related reagents in reaction with alkyl halides has been reported and used for the preparation of a variety of phosphonic acid analogues of phospholipids.114119-124 Interestingly, alkyl chlorides appear to be more reactive with the silyl reagents than do alkyl iodides, a reversal of the normally observed trend with alkyl esters of the phosphorus acids. (The particular use of silyl phosphorus reagents for the synthesis of biologically significant compounds has... 

Electrophilic substitutions on thiophene, like those on benzene, can be carried out only in the presence of catalysts. In reactions with sulfenyl halides, SnCl4 proved to be particularly suitable in the case of the less reactive sulfenyl halides, Grignard reactions lead to the desired products ... 

Radical cyclization is an effective approach to the synthesis of isoquinolines (Scheme 8). In some cases these offer an alternative to the palladium-catalyzed reactions with aryl halide intermediates <99EJOC1925, 99TL1125>. For example, the radical cyclization of the iodide 37 onto the vinylsulfide moiety was followed by a cascade cyclization to form the benzo[n]quinolizidine system <99TL1149>. In some cases the radical cyclization can take place without the need for a halo intermediate. The reactive intermediate of 38 was formed on the nitrogen as an amidyl radical, which underwent tandem cyclizations to the lycorane system <99TL2125, 99SL441>. 

Recently, however, Tokitoh and co-workers " °° reported a versatile reactivity of Tbt-substituted plumbylenes 182a-d, that is, insertion reactions with alkyl halides, diphenyl dichalcogenides, bromine abstraction from carbon tetrabro-mide, and sulfurization with elemental sulfur as shown in Scheme 14.83. 

This reaction, designed by Gilbert Stork, fosters monoalkylation. Enamines —[see Problem 17.5(a)(5)], of ketones are monoalkylated with reactive halides, such as benzyl and allyl, in good yield at the a C. The enamines are made from the ketone and preferably a 2° amine, RjNH. 

Generally, tin vapor appears only slightly more reactive than finely divided tin in its reactions with organic halides (55). 

Since reactive species such as H , OH, and R would be formed in greater concentrations at ignition temperatures than at lower temperatures, their reactions with hydrogen halides (shown below) would be important in ignition. 

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