Formals, diaryl

A high yield synthesis involving formal oxidation of a sulphoxide to a sulphoximine has been reported183 using O-mesitylenesulphonyl hydroxylamine (NH2OMes) (equation 67). The reaction is successful for a wide range of sulphoxides including dialkyl, diaryl and cyclic species. 

Thermolysis of the Rti(IV) dialkyl or diaryl porphyrins M(Por)R2 at 100 C in benzene leads to loss of one of the axial lieands and formal reduction of the... 

Fischer, M. Wan, P. m-Quinone methides from m-hydroxy-1,1-diaryl alkenes via excited-state (formal) intramolecular proton transfer mediated by a water trimer. J. Am. Chem. Soc. 1998, 120, 2680-2681. 

Diaryl carbazides and thiocarbazides, e.g., 43, can be oxidized at alkaline pH to yield C-hydroxy or C-mercapto formazans (44) (Eq. 8).68,129 The replacement of C-halo formazans is considered to be a better method60 for the preparation of 44. A class of cyclic formazans (45) can be obtained by air oxidation of amidrazones (46) (Eq. 9) 9,73,101,102 jhough this is formally a formazan, there are no reports of its oxidation reactions. In a... 

Azomethine ylides undergo a formal [3 + 2] cycloaddition with carbonyl compounds to provide oxazolines. Thioimidates, in particular, are effective as ylide precursors. For example, Kohra and co-workers reported that the thioimidate 260, upon activation with cesium fluoride, reacts with aromatic aldehydes and diaryl-ketones to provide oxazolines 261 in modest to good yields. Aliphatic aldehydes and simple ketones are unreactive (Scheme 8.72). 

The fluorescence properties of 2,2-diaryl-substituted l-(9-anthryl)-ethylenes 87c-e differ markedly from those of 87a, b by a decrease in the quantum yields of emission, and by the loss of vibrational fine structure of the emission spectra, which is associated with a dramatic increase of the Stokes shifts. For the 2,2-diphenyl derivative 87c in cyclohexane solution, the quantum yield is 0.29, and the Stokes shift is 5600cm-1. For 9-anthryl-ethylene 87e, in which the formal conjugation has been extended by a terminal methylene group, the quantum yield in cyclohexane is as low as... 

The electrochemical oxidation of 2,5-diaryl-1,4-dithiins (50) has been studied using various voltametric techniques and all compounds were found to undergo quasi-reversible one-electron transfers to the radical cations and dications.126 The first formal redox potential and the lifetime of the radical cation were found to decrease with increasing electron donation from the aryl ring. The major products were the 2,2 -dimers, which result via reaction of two radical cations for which rate constants are given. Dibenzothiophene radical cations reacted with tetranitromethane under... 

A different sequential DreM pathway involving O-carbamate ring switch-vinylogous tolyl amide cydization, 170 —> 171 —> 172 (Scheme 44), a formal bridging of a 2,2 -methyl diaryl dicarbanion with a carbonyl dication equivalent (173) has been affirmed in a model study (174 —> 175, Scheme 45) [73] and applied in natural product total synthesis [73, 74]. 

Diaryl ditellurium reacted with carbon monoxide at elevated pressures in acetonitrile in the presence of dicobalt octacarbonyl at 125° to give the diaryl tellurium and the Je-aryl tellurolobenzoate12. Formally, these reactions can be considered to be a replacement of one tellurium atom in the diaryl ditellurium by carbon monoxide. Didodecyl ditellurium produced only didodecyl tellurium and no 7e-dodecyl tellurolotridecanoate12. 

A special case of conjugate addition involves diaryl ketones. As noted in Section 4.2, conjugate addition of organomagnesium compounds may lead to products formally derived from addition to a ring. Such reactions are favoured by conditions promoting electron transfer, particularly when polar addition to the carbonyl group is sterically hindered [3]. 

Bis(a-chloroarylidene)hydrazines or 1,2-diaryl-1,2-dichloroethenes [a formal dimer of aryl(chloro)carbene] were sometimes observed as side products when 3-aryl-3-chloro-3/7-di-azirines were decomposed in alkenes. 

Suzuki coupling, e.g., I(OH)Ots [186] I > Br or OTF. Diaryl iodonium salts were also reported to couple with various staimanes at r.t. catalyzed by Cul, and therefore have reactivity similar to other formal iodine(I) species [30]. Several extremely effective catalysts are air stable Pd2dba3-CHCl3, Pd(OAc)2, and Pd(PhCN)2Cl2 in conjunction with AsPh3 [4, 9, 10, 75, 187, 188, 189] other co-catalysts, such as trifurylphosphine PPh3 in the absence of Cu salts, were much less effective [75,... 

The reaction scheme was studied by carrying out tests at increasing reaction times, as shown in Figure 2. The guaiacol conversion increases as reaction time increases. The reaction scheme consists of parallel reactions for the formation of the three vanillol isomers and of by-products. The latter are mainly constituted of monoaryl products obtained by reaction between vanillols and methanol or hemi-formal. These are consecutive reactions from a chemical point of view, but are parallel ones from a kinetic point of view, since they occur extensively even at low guaiacol conversion therefore they likely occur in the zeolite pores before vanillols diffuse back into the liquid phase. Consecutive reactions mainly involve p-VA, with formation of by-products which consist of diaryl and of monoaryl compounds. 

The elimination to diene is a competing pathway in all these reactions. If triethylamine is employed as the amine and/or the 1,3-diene has an electron-withdrawing group in the 1-position, diene foimation predominates. For example, ( , )-penta-2,4-dienoic acid reacted with aryl bromides in the presence of triethylamine and the palladium catalyst to give (E,E)-5-arylpenta-2,4-dienoic acid in good yield. The propensity for elimination to diene was later developed into a 1,4-diarylation of 1,3-dienes [Eq.(18)] [36]. This is formally a palladium-... 

Finally there are a number of papers dealing with photoreactions of diaryl-cyclopropenes and arylindenes, which formally involve migration of a carbon group from the side-chain to the ortho-position of an aromatic ring. An example of the basic reaction is the formation of indenes when 1,3-diphenylcyclopropenes (199) are irradiated directly. Now it is shown that isomeric indenes are formed when the reaction is carried out in the presence of 9,10-dicyanoanthracene, and an electron-transfer mechanism is invoked to account for the change of product. In a separate paper concerned largely with intramolecular photocycloaddition reactions, cyclopropenes (199 R = allyl) are reported to give both types of indene on direct irradiation, via the normally postulated vinylcarbene intermediate. The... 

Figure 1 Polymer interpretation chart. PAI, polyamideimide PC, polycarbonate UP, unsaturated polyester PDAP, diarylate phtalate resin VC-VAc, vinyl chloride-vinyl acetate copolymer PVAc, polyvinyl acetate PVFM, polyvinyl formal PUR, polyurethane PA, polyamide PMA, methacrylate ester polymer EVA, ethylene-vinyl acetate copolymer PF, phenol resin EP, epoxide resin PS, polystyrene ABS, acrylonitrile-butadiene-styrene copolymer PPO, polyphenylene oxide P-SULFONE, poly-sulfone PA, polyamide UF, urea resin CN, nitrocellulose PVA, polyvinyl acetate MC, methyl cellulose MF, melamine resin PAN, polyacrylonitrile PVC, polyvinyl chloride PVF, polyvinyl fluoride CR, polychloroprene CHR, polyepichlorohydrin SI, polymethylsiloxane POM, polyoxy-methylene PTFE, polytetrafluoroethylene MOD-PP, modified PP EPT, ethylene-propylene terpolymer EPR, ethylene-propylene rubber PI, polyisoprene BR, butyl rubber PMP, poly(4-methyl pentene-1) PE, poly(ethylene) PB, poly(butene-l). (Adapted from Ref. 22, p. 50.)...

In 1974, McKillop and co-workers reported the formation of diphenox3nnethane derivatives from the attempted alkylation of p-Jt-butylphenol with benzyl chloride and a catalytic amount of a phase transfer catalyst (PTC) in methylene chloride. More recently, Dehmlow and Schmidt reported the synthesis of a series of dlalkyl and diaryl formals ( from the reaction of alkoxide and phenoxide anions with methylene chloride in the presence of a phase transfer catalyst (equation 5). For example, reaction of 2,3,5-trimethylphenol, powdered potassium hydroxide... 

Silagermenylidene (181) has been synthesized by reductive dehalogenation of a diaryl substituted dichlorosilane in the presence of an NHC-stabilized dichloro germanium and isolated in 8% yield, representing higher analogue of vinylidene which has so far only been detected trapped in matrix. Its formal [2+2] cycloaddition with phenylacetylene has been carried out and afforded germylene (182). ... 

The second type of radical photoinitiators is the so-called bimolecular photoinitiators that consist of a diaryl ketone together with a compound that provides easily abstractable hydrogen atoms. The most common of these photoinitiators consists of benzophenone or a substituted benzophenone in combination with an aliphatic tertiary amine. A proposed mechanism for the formation of radicals by these bimolecular photoinitiators is depicted in Scheme 10. Photoexcitation of benzophenone results in the formation of triplet-state benzophenone that forms a charge transfer complex, 22, with triethanolamine. Formal electron transfer takes place with the subsequent formation of a radical cation-radical anion... 

The protonic acid needed to initiate the chain reaction is usually produced by UV irradiation of diaryl-iodonium or triarylsulfonium salts. The photolysis reaction, which produces both Brdnsted acid and free radicals in the presence of a hydrogen donor molecule, can be formally written as follows for the iodonium salt ... 

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