Reactions with electrophilic oxidants

Diels-Alder reactions, 4, 842 flash vapour phase pyrolysis, 4, 846 reactions with 6-dimethylaminofuKenov, 4, 844 reactions with JV,n-diphenylnitrone, 4, 841 reactions with mesitonitrile oxide, 4, 841 structure, 4, 715, 725 synthesis, 4, 725, 767-769, 930 theoretical methods, 4, 3 tricarbonyl iron complexes, 4, 847 dipole moments, 4, 716 n-directing effect, 4, 44 2,5-disubstituted synthesis, 4, 116-117 from l,3-dithiolylium-4-olates, 6, 826 electrocyclization, 4, 748-750 electron bombardment, 4, 739 electronic deformation, 4, 722-723 electronic structure, 4, 715 electrophilic substitution, 4, 43, 44, 717-719, 751 directing effects, 4, 752-753 fluorescence spectra, 4, 735-736 fluorinated derivatives, 4, 679 H NMR, 4, 731 Friedel-Crafts acylation, 4, 777 with fused six-membered heterocyclic rings, 4, 973-1036 fused small rings structure, 4, 720-721 gas phase UV spectrum, 4, 734 H NMR, 4, 7, 728-731, 939 solvent effects, 4, 730 substituent constants, 4, 731 halo... 

The highly 7r-deficient character of the 1,2,4-triazine ring increases the nucle-ophilicity of the methyl group in methyl-1,2,4-triazine A-oxides in reactions with electrophilic alkenes and aldehydes. Thus treatment of the 6-methyl-3-phenyl-1,2,4-triazine 4-oxide 113 with l-(dimethylamino)-l-ethoxyethylene leads to the... 

The introduction of substituents into the 1- and 2- positions of thianthrene can be achieved by deprotonation at C-1 and subsequent reaction with electrophiles and by formation of 2-lithiothianthrene from the corresponding bromo compound <96JCS(P1)2391>. Selective oxidation of both thianthrene and its 5-oxide have been described <96CEJ255, 96JCS(P1)2693>. 

The group R1 can be allyl, acyl, or alkynyl, and arynes can also act as the acceptors. The catalysts are usually Ni(cod)2, or ligated palladium. The mechanisms are not understood in detail, but a catalytic cycle involving the product of oxidative addition, Sn-M-R1, is thought to be involved. The stannylalkenes that are formed can then be subjected to reaction with electrophiles (e.g., AczO or RCH=0), or to coupling reactions in the presence of transition metals (e.g., the Stille reaction). 

The furoxan ring is more susceptible to nucleophilic attack and reduction than it is to reaction with electrophiles or oxidation. Grignard reagents react with disubstituted furoxans primarily at C-3 and, in most cases, the resulting adduct fragments to a nitrile and a nitronate salt which affords a ketone on workup. 

Substituted 5-aminotetrazoles Reactions with electrophiles and oxidation... 

REACTIONS WITH ELECTROPHILES AND OXIDIZING AGENTS 2.07.3.1 Piperidines... 

General chemical properties of triazolopyridines, such as oxidations, reductions, reaction with electrophiles, reactions with nucleophiles, homolytic reactions, ring-opening reactions, and photochemical reactions can be found in <2002AHC(83)2>. 

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... 

Reactions of cyclophosphines may be divided into three types (a) those that involve retention of the initial ring size, (b) those in which a P-P bond is cleaved and (c) those that result in a change in ring size, i.e. ring expansion or ring contraction. The former type (a) is observed for reactions with electrophilic reagents in which the lone pairs on the phosphorus(III) centres provide the nucleophilic site. These may involve simple adduct formation or oxidation to phosphorus(V) in some cases this oxidation may be accompanied by ring... 

The key success of these metal-catalyzed processes lies in the replacement of an unachievable carbozincation by an alternative carbometallation involving the transition metal catalyst, or another pathway such as an alkene-alkene (or alkyne) oxidative coupling promoted by a group IV transition metal complex, followed by transmetallation. An organozinc is ultimately produced and the latter can be functionalized by reaction with electrophiles. 

A behavior similar to that of pyridine and pyrazine N-oxides is exhibited by complexes of pyridines with hexafluoroacetone. Such complexes are expected to enhance the acidity of the pyridine hydrogens by oxygen-lithium chelating effects and therefore direct 2-deprotonation. In fact, treatment of f-butylpyridine (495) with LiTMP/THF-Et20/- 107°C generated, via the known complex 507, the stable 2-lithio species 508 which, upon reaction with electrophiles, furnished 2-substituted pyridines 509 (Scheme 154) (83JOC4156). 

Living polymers usually require special reagents to achieve termination. Any electrophilic reagent that reacts with the carbanion active center and also allows preparation of polymers with desired terminal functionalities can be used for this purpose.168,174,181 Hydrogen-terminated polymers can be produced by proton donors, whereas carbon dioxide results in a carboxylate end group. Terminal alcohol functionalities can be formed through reaction with ethylene oxide and carbonyl compounds. 

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