3.4- Diaroyl

Auf UV-Spektren von eyclisehen 3-Acyl-78, 3-Alkyl-79, 4-Amino-3-aryl-80, 3,4-Dialkyl-81, 3,4-Diaryl-81 und 3,4-Diaroyl-furazan-2-oxiden82 (sowie Lit.83) sei hingewiesen. 

Annelation of a pyridine nucleus onto a preformed l,2,5-thia(selena or oxa)diazole unit has been accomplished (Scheme 44). Specifically, 3,4-diaroyl[l,2,5]heteradiazoles (236)-(238) react with alkylamines under either basic or acidic conditions to afford [l,2,5]heterodiazolo[3,4-c]pyridines (240)-(242) in moderate to good yields (Table 13) <79S687, 80S842, 83H(20)1285, 89JHC215). These cyclizations occur via an intermediate or/Zto-iminoketone (239). 

Thiadiazolopyridines, e.g. (32), result from the base-catalysed reaction of alkylamines with 3,4-diaroyl-thiadiazoles, e.g. (31), (Scheme 15). The yield of compound (32) is 88%, but the corresponding oxadiazolopyridine is only obtained in 13% yield. As many diaroyl-substituted five-membered heterocycles are easily obtainable from 1,3-dipolar cyclization reactions with diaroyl-alkynes, this reaction may provide a useful method for preparing fused pyridines. ... 

Furoxans, bis[(acetoxyalkyl)carbonyl]-synthesis, 6, 421 Furoxans, bisarylsulfonyl-synthesis, 6, 423 Furoxans, bis(dialkylamino)-synthesis, 6, 414 Furoxans, butylhexynyl-synthesis, 6, 423 Furoxans, decamethylenering cleavage, 6, 405 Furoxans, diacyl-thermolysis, 6, 81 synthesis, 6, 442 Furoxans, diadamant-1-yl-ring cleavage, 6, 404 Furoxans, dialkoxycarbonyl-synthesis, 6, 423 Furoxans, dialkyl-synthesis, 6, 423 Furoxans, diaryl-ozonolysis, 6, 405 Furoxans, diaroyl-isoxazoles from, 6, 82 Furoxans, dibenzoyl-synthesis, 6, 423 Furoxans, diethoxycarbonyl-synthesis, 6, 423... 

Thiophene, 2,4-diamino-3,5-dicyano-synthesis, 4, 889, 924 Thiophene, 2,5-diamino-3,4-dicyano-synthesis, 4, 119, 888, 889 Thiophene, 2,5-diaroyl-... 

Only a few diacvl peroxides see widespread use as initiators of polymerization. The reactions of the diaroyl peroxides (36, R=aryl) will be discussed in terms of the chemistry of BPO (Scheme 3.25). The rate of p-scission of thermally generated benzoyloxy radicals is slow relative to cage escape, consequently, both benzoyloxy and phenyl radicals are important as initiating species. In solution, the only significant cage process is reformation of BPO (ca 4% at 80 °C in isooctane) II"l only minute amounts of phenyl benzoate or biphenyl are formed within the cage. Therefore, in the presence of a reactive substrate (e.g. monomer), tire production of radicals can be almost quantitative (see 3.3.2.1.3). 

Diacyl peroxides may also undergo non-radical decomposition via the carboxy inversion process to form an acylcarbonate (Scheme 3.27).46 The reaction is of greatest importance for diaroyl peroxides with electron withdrawing substituents and for aliphatic diacyl peroxides (36) where R is secondary, tertiary or ben/,yl.157 The reaction is thought to involve ionic intermediates and is favored in polar solvents 57 and by Lewis acids.158 Other heterolytic pathways for peroxide decomposition have been described.150... 

Aroyloxy radicals are formed by thermal or photochemical decomposition of diaroyl peroxides (see 3.3.2.1) and aromatic peroxyesters (3.3.2.3) (Scheme 3.78) alkoxycarbonyloxy radicals are similarly produced from peroxydicarbonates (33.2.2). 

A wide range of dialkyf7 and diaryl disulfides,58 59 diaroyl disulfides,00 and xanthogens61 has been used as transfer agents (Scheme 6.8). Their use ideally leads to the incorporation of functionality at both ends of the polymer chain, thus they find application in the synthesis of tclcchclics (Section 7.5.2). 

Dimethyl-I,l -biphenyl has been prepared by a wide variety of procedures, but few of these are of any practical synthetic utility Classical radical biarjl syntheses such as the Gomberg reaction or the thermal decomposition of diaroyl peroxides give complex mixtures of products m which 4,4 dimethyl-l.l -biphenyl is a minor constituent A radical process maj also be involved in the formation of 4,4 dimethyl-1, l -biphenyl (13%) by treatment of 4-bromotoluene with hydrazine hydrate 5 4,4 -Dimethyl-l,l -biphenyl has been obtained in moderate to good yield (68-89%) by treatment of either dichlorobis(4-methyl phenyl)tellurium or l,l -tellurobis(4-methylbenzene) with degassed Raney nickel in 2 methoxyethyl ether 6... 

Aroylnitrile oxides can also be generated from diaroyl furoxans 183 under micro-wave irradiation [33]. Formation of the nitrile oxide intermediate 184 and its cycloaddition with dipolarophiles proceeds at atmospheric pressure within minutes in the absence of solvent and in good yields (Scheme 9.56). The reaction occurs by the rear-... 

Diaryl- (85), diaroyl- (71), bis(4-substituted-l,2,5-oxadiazol-3-yl)furoxans (104) as well as exotic l,2,2,5,5-pentamethyl-4-(nitromethyl)-3-imidazoline 3-oxide-derived furoxan 22 (105) were obtained via corresponding nitrile oxides. 

Imidoyl esters (Scheme 3.7) are obtained readily when the appropriate imidoyl chloride is reacted with an alcohol or phenol under basic conditions in the presence of phase-transfer catalysts [71]. The reaction with thiophenol yields the corresponding thioimidoyl ester. Diaroyl amides are produced by the analogous reaction of the imidoyl chloride and carboxylate anions. In this reaction, the initially formed carboxylic ester undergoes a 1,3-migration to produce the amide. 

Diaroyl and 3,5-diacyl-1,2,4-thiadiazoles (98) can be hydrolyzed with NaOH giving 3-mono-substituted ketones (99) (Equation (14)) <92JHC1433>. 

Reaction of tetrasulfur tetranitride with aryl and alkyl bromomethyl ketones (288) in refluxing chlorobenzene gives 3,5-diaroyl and 3,5-diacyl-l,2,4-thiadiazoles (98) in yields of 17-60% (Equation (44)) <92JHC1433>. 

Eberson introduced the concept of a dissociative ET to peroxides some time ago. There have been attempts to apply Marcus Theory to the ET reduction of diaroyl peroxides in connection with the mechanism of the chemically initiated electron exchange luminescence (CIEEL)." " The... 

J -Bipyrroles. Oxidation of 1-aroylpyrroles (I) with Pd(OAc)2 in HOAc results in l,l -diaroyl-2,2 -bipyrroles (2), which are hydrolyzed by acidic aqueous methanol to 2,2 -bipyrroles (3). 

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