Reaction with electrophilic agents

Electron deficient carbon-carbon double bonds are resistant to attack by the electrophilic reagents of Section 5.05.4.2.2(t), and are usually converted to oxiranes by nucleophilic oxidants. The most widely used of these is the hydroperoxide ion (Scheme 79). Since epoxidation by hydroperoxide ion proceeds through an intermediate ct-carbonyl anion, the reaction of acyclic alkenes is not necessarily stereospecific (Scheme 80) (unlike the case of epoxidation with electrophilic agents (Section 5.05.4.2.2(f)) the stereochemical aspects of this and other epoxidations are reviewed at length in (B-73MI50500)). 

Azafulvaleiies of type 7-10 constitute electron-poor compounds therefore, only a few reactions using electrophilic agents have been described. Tlius, heating 26a with methyl iodide or benzoyl chloride and subsequent treatment of the resulting products with FIBF4 gave the dithiolium salts... 

Another formylation reaction, which is named after Gattermann, is the Gatter-mann-Koch reaction. This is the reaction of an aromatic substrate with carbon monoxide and hydrogen chloride (gas) in the presence of a Lewis acid catalyst. Similar to the Gattermann reaction, the electrophilic agent 9 is generated, which then reacts with the aromatic substrate in an electrophilic aromatic substitution reaction to yield the formylated aromatic compound 10 ... 

REACTIONS WITH ELECTROPHILES AND OXIDIZING AGENTS 2.07.3.1 Piperidines... 

Reactions with Electrophiles, including Oxidizing Agents 375... 

Reaction with Electrophiles, including Oxidizing Agents 5.13.3.3.1 Electrophilic interactions at the ring oxygen atom... 

Reaction of II with electrophilic agents, HN03, SOs, and CH20 in concentrated sulfuric acid, and with bromine in acetic acid, yielded the mono- or poly-substituted complexes, depending upon the reaction conditions (16). The position of substitution in these complexes was established by permanganate oxidation to the benzoic acids, esterification of the acids with diazomethane, and sub-... 

The reaction of a citronellic ester enolate with electrophilic agents gives open-chain fluorinated products 32 and 33 only.11 The absence of rearranged fluorinated products in this system, a potential precursor to a 5-hexenyl-type radical clock, indicates that free radicals are not intermediates in the path to fluorinated products.12... 

Studies on reactions of fused tetrazoles with electrophilic agents are few, presumably due to the capability of these compounds to enter into various transformations <1998JPR687>. It was found <1999JST(477)119> that tetra-zolo[l,5- ]pyridine 13 and its substituted derivatives undergo alkylation with dimethyl sulfate to give the iV -methyl compounds 229 as the prevailing isomer. Only when R = H is a small amount of the iVz-methyltetrazolo[l,5-tf]-pyridinium salt obtained (Equation 33) <1999JST(477)119>. 

The insight that zinc ester enolates can be prepared prior to the addition of the electrophile has largely expanded the scope of the Reformatsky reaction.1-3 Substrates such as azomethines that quaternize in the presence of a-halo-esters do react without incident under these two-step conditions.23 The same holds true for acyl halides which readily decompose on exposure to zinc dust, but react properly with preformed zinc ester enolates in the presence of catalytic amounts of Pd(0) complexes.24 Alkylations of Reformatsky reagents are usually difficult to achieve and proceed only with the most reactive agents such as methyl iodide or benzyl halides.25 However, zinc ester enolates can be cross-coupled with aryl- and alkenyl halides or -triflates, respectively, in the presence of transition metal catalysts in a Negishi-type reaction.26 Table 14.2 compiles a few selected examples of Reformatsky reactions with electrophiles other than aldehydes or ketones.27... 

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