Aryl chlorides vinyl substitutions

Further substitution possibilities are available from 2-(trimethylsilyl)methyl-2-propenal, prepared in 71 % yield by Swern oxidation of 2-(trimcthylsilyl)methyl-2-propenol23. Reaction with trimethylsilyl cyanide/zinc(II) iodide, aryl- or vinyllithium followed by acetyl chloride, allows access to cyano-, aryl- or vinyl-substituted congeners. 

With aluminum or zinc and aluminum chloride in acetonitrile, dimerization of the ketyl is followed by rearrangements to benzopinacolones.m The reaction proceeds via an epoxide, which becomes the major product in the presence of ethylaluminum dichloride. Aryl or vinyl substituted carbonyl compounds dimerize sonochemically in the presence of TMSCl and zinc in ethers. Pinacol disilyl ethers are obtained in yields higher than those of the silent reaction. 12,113... 

Pretreatment with nickel bromide causes normally unreactive aryl chlorides to undergo Pd-catalyzed substitution,139 and aryl and vinyl triflates have been found to be excellent substrates for Pd-catalyzed alkenylations.140... 

A number of methods for the preparation of vinyl and allyl sulfones are available [1U9, 110], and the syntheses of vinyl sulfones from alkenes has been reviewed [116]. A simple one-step procedure of wide applicability makes use of a palladium-catalysed cross-coupling reaction between aryl and alkyl sulfonyl chlorides and substituted vinyl and allyl stannanes... 

Vinyl Substitutions with Carboxylic Acid Halides, Aryl Sulflnates and Arylsulfonyl Chlorides 856... 

Normally, the most practical vinyl substitutions are achieved by use of the oxidative additions of organic bromides, iodides, diazonium salts or triflates to palladium(0)-phosphine complexes in situ. The organic halide, diazonium salt or triflate, an alkene, a base to neutralize the acid formed and a catalytic amount of a palladium(II) salt, usually in conjunction with a triarylphosphine, are the usual reactants at about 25-100 C. This method is useful for reactions of aryl, heterocyclic and vinyl derviatives. Acid chlorides also react, usually yielding decarbonylated products, although there are a few exceptions. Likewise, arylsulfonyl chlorides lose sulfur dioxide and form arylated alkenes. Aryl chlorides have been reacted successfully in a few instances but only with the most reactive alkenes and usually under more vigorous conditions. Benzyl iodide, bromide and chloride will benzylate alkenes but other alkyl halides generally do not alkylate alkenes by this procedure. 

A very few examples of the use of aryl-tin,21 -lead,21 -lithium43 and -magnesium21143,44 derivatives as the source of the aryl group in vinyl substitutions have been reported. Tin derivatives have been used with palladium dichloride bis(benzonitrile) and a copper(II) chloride reoxidant in a regioselective synthesis of oxygen heterocycles from unsaturated alcohols.43... 

The effectiveness in carbonylations of Ni(CO)4 is well documented, as well as its toxicity. Substitutes for this catalyst are therefore of much interest, and [Ni(CN)(CO)J], generated in situ from Ni(CN)2, CO and aqueous NaOH under phase transfer conditions, fulfills this role in many cases394. Under these conditions (1 atm CO), several types of organic halides are carbonylated, including allyl halides394, benzyl chlorides (with lanthanide salts)395, aryl iodides396, vinyl bromides397 and dibromocyclopropanes (equation 199)398. 

Numerous aryl bromides, iodides [203], borates [204] and triflates [205, 206] have been successfully carbonylated. Triflates could serve as a route for the synthesis of arenecarboxylic acid derivatives from phenols. This carbonylation using dppf in a catalytic mixture generally shows higher efficiency than PPhj or P(o-Tol)3 [207]. Poor performance is also noted for PPhj in a Pd-catalyzed vinyl substitution of aryl bromides [208]. Side-reactions involving the formation of [PPhjAr]Br and ArH are responsible. A system which is catalyzed effectively by PdCljfdppf) under 10 atm CO is the desulfonylation of 1-naphthalenesulfonyl chloride 58 in the presence of Ti(OiPr)4. Formation of isopropyl 1-naphthoate 59 can be explained in a sequence of oxidative addition, SOj extrusion, carbonylation and reductive elimination (Fig. 1-27) [209]. A notable side-product is di-l-naphthyl disulfide. 

There is good evidence that some nucleophilic substitution reactions do involve a single electron transfer, but the best established use a slightly different mechanism. These are the SrnI reactions, with the subscript RN standing for radical nucleophilic. Examples are the reaction of the nitronate anion 4.14 with p-nitrobenzyl chloride 4.15, 251 and the reaction of the pinacolone enolate 4.16 with bromobenzene.252 The former might have been a straightforward SN2 reaction, but actually takes the S l pathway because the nitro groups make the electron transfer exceptionally easy. The latter cannot take place by a conventional Sn2 reaction, because aryl (and vinyl) halides are not susceptible to direct displacement, and the S l pathway overcomes this difficulty. 

In the presence of TBAF and electron-rich Pd phosphine coirplexes, aryl chlorides react smoothly with arylchlorosilanes and alkenylchlorosilanes to form substituted arenes. The starting (E or Z) geometry of C-C double bond of alkenylchlorosilanes was maintained in the products (eq 34). Trimethox)rvinylsilane was also used in arene vinylation (eq 35), though homocoupling side products were observed with this reagent. ... 

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