1.3- dicarbonyl compounds reaction with toluene

Becker has performed detailed product studies on the OH reaction with toluene and p-xylene. At present, product formation can best be explained by the mechanism shown in Fig. 10 where muconaldehydes (hexa-2,4-diene-1,6-dial) are proposed as direct products of the reaction of the aromatic-OH adduct with O2. Several of these muconaldehydes have been synthesised and their reactions with OH radicals investigated (Becker). These reactions result in the formation of unsaturated 1,4-dicarbonyl compounds, glyoxal, methylglyoxal and maleic anhydride, which have also been observed in the reaction of OH with toluene and p-xylene. It has been demonstrated that the unsaturated 1,4-dicarbonyl species react very rapidly with OH and photolyse, yielding products which possibly accelerate O3 formation in smog chamber type studies. Many of the aromatic oxidation products especially the unsaturated 1,6-dicarbonyl species are known either to be toxic or are potentially toxic with both carcinogenic and mutagenic properties [8]. 

When R2 substituent is flourocontaining alkyl group, the transformation 17 18 becomes hindered and its proceeding requires some special methods. For example, in [48] Biginelli-like cyclocondensations based on three-component treatment of 3-amino-l,2,4-triazole or 5-aminotetrazole with aldehydes and fluorinated 1,3-dicarbonyl compounds were investigated. It was shown that the reaction can directly lead to dihydroazolopyrimidines 20, but in the most cases intermediate tetrahydroderivatives 19 were obtained (Scheme 10). To carry out dehydration reaction, refluxing of tetrahydroderivatives 19 in toluene in the presence of p-TSA with removal of the liberated water by azeotropic distillation was used. The same situation was observed for the linear reaction proceeding via the formation of unsaturated esters 21. 

Such hydroxyimidazoles or oxides are capable of complete reduction to the unoxygenated imidazoles, while the 1-hydroxyimidazole 3-oxides can also be partically reduced with, for example, NaBUi [53], or completely deoxygenated with Raney nickel [52, 54], Although most cyclizations of a-ketooximes lead to A -oxygenated imidazoles, there are exceptions. When an o(-oximino-)6-dicarbonyl compound is refluxed with benzylamine in a suitable solvent (c.g. DMSO, acetonitrile, toluene), 4-acylimidazoles (11) are formed in moderate to good yields. The reaction is readily adapted to the synthesis of imidazole-4-carboxylates and -amides (Scheme 4.1.7)... 

A new synthesis of corydolactam (19) ( alkaloid P ) has been reported (Scheme 2). Advantage was taken of a known reaction of 1-toluene-p-sulfonylaziridine (16) with j8-dicarbonyl compounds to prepare the pyrrolidone (17), which upon ketalization and detosylation yielded (18), a compound previously transformed in two steps into corydolactam (19). 

Guanidines have also been employed as catalysts in Michael reactions with enones and, for example, bicyclic guanidine 86 has been found to perform well in the Michael reaction of different 1,3-dicarbonyl compounds with cyclo-pentenones, providing the final Michael adducts with excellent yields and enantioselectivities (Scheme 4.33). In this case, the authors found that the use of triethylamine as solvent resulted in a dramatic increase in the rate of the reaction, without affecting significantly its stereochemical outcome with respect to the same reaction in toluene, which is the usually chosen solvent when working with this type of catalyst. 

Polymer-supported Reagents. Polymer-supported toluene-sulfonyl azide I3I was prepared by reaction of a macroreticular p-toluenesulfonyl chloride resin (prepared, in turn, by chlorosul-fonation of Amberlite XE 305) with excess sodium azide. Resin 13, a solid-phase equivalent of />-toluenesulfonyl azide, can be used for diazo transfer to /3-dicarbonyl compounds (eq 14). Unlike tosyl azide, resin 13 does not detonate on shock treatment and is stable at room temperature. Recently, an analogous benzenesul-fonyl azide resin has been prepared from PS-TsCl. ... 

Notably, this methodology can be used for the regioselective CDC reaction of toluene derivatives with activated methylene compounds. Using the system [FeC (10 mol%), ( BuOO Bu) (2 equiv.), toluene, 120 °C for 24 h], 41% of the allq lated 1,3-dicarbonyl compound was obtained. The best catalytic system was based on Fe(OAc)2 (10 mol%) in combination with 4 equiv. of BuOO Bu (Scheme 4.5). 

A (1/7-imidazol-l-yl) silver species (55) has been postulated as the key intermediate in the 3-l-2-cycloaddition reaction of diazoalkanes (54) with benzynes yielding 2-aryl-2H-indazoles (56) (Scheme 18). The 3-I-2-cycloaddition reaction of 3-trifluoromethyl-4-diazopyrazolinones with dialkyl acetylene dicarboxylates, in refluxing toluene, produced spiro 3/f-pyrazole adducts that rearranged to the trifluoromethyl-substituted pyrazolo[l,5-fi(][l,2,4]triazin-7-ones. ° The 1,3-dipolar cycloaddition reaction of aromatic thioketones (58) with 2-aza-1,3-dicarbonyl compounds (57), at 20-50 C, yielded thiadiazoline adducts (59) that readily eliminate nitrogen to produce oxathioles (60) in moderate yields (up to 70%) (Scheme 19). ... 

A related three-coordinate dicarbonyl-carbene complex can be obtained by reaction of Ni(CO)4 with the carbodi-phosphorane double ylide Ph3=C=PPh3. The reaction of Ni(GO)4 with Ph3=C=PPh3 in toluene gives the tricarbonyl complex Ni G(PPh3)2 (CO)3, but in THF solvent the deep red 16-electron three-coordinate complex Ni G(PPh3)2 (GO)2 was obtained. Both the three- and four-coordinate compounds Ni G(PPh3)2 (GO) , n = Z, 3) were structurally characterized by X-ray diffraction. ... 

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