Azulene yield

Shemdal considers the formation of a crystalline picrate, melting at 122°, the best method of identifying azulene. On reduction azulene yields a dihydro-sesquiterpene, and in Sherndal s opinion, it is... 

Oxidation of thiophene with peracid under carefully controlled conditions gives a mixture of thiophene sulfoxide and 2-hydroxythiophene sulfoxide. These compounds are trapped by addition to benzoquinone to give ultimately naphthoquinone (225) and its 5-hydroxy derivative (226) (76ACS(B)353). The further oxidation of the sulfoxide yields the sulfone, which may function as a diene or dienophile in the Diels-Alder reaction (Scheme 88). An azulene synthesis involves the addition of 6-(A,A-dimethylamino)fulvene (227) to a thiophene sulfone (77TL639, 77JA4199). 

Further purification of azulene may be achieved by sublimation at reduced pressure, mp 99 C. The checkers found that mechanical losses, particularly as mentioned in Note 9, lead to reduction in yield with reduction in scale (0.1 mol, 39% yield 0.5 mol, 43% yield 0.8 mol, 79% yield). 

Azulyl sulphoxides 127 have also been prepared by a reaction involving a direct electrophilic substitution on the azulene ring by alkane- or arenesulphinyl chlorides186 (equation 69). Preparation of the methyl and phenyl sulphoxides of 4,6,8-tri-methylazulene and 4,6,8-tri-isopropylazulene by this method resulted in fair yields (57— 72%). However, the substitution on azulene itself gave only low yields of the corresponding sulphoxides. 

Azulene quinones [49b] are compounds related to the family of tropones and are considered to possess great biological and physiological potential. Several polycyclic compounds have been prepared by high pressure (3kbar, PhCl, 130°C, 15h) Diels-Alder reaction of 3-bromo-l,5-azulene quinone (137) and 3-bromo-l,7-azulene quinone (138) with several dienophiles. The cycloadditions were regioselective and afforded cycloadducts in reasonable to good yields (Scheme 5.20). 

C-TMS protection of the alkyne provided acceptable yields of 3-substituted indole as long as the hydroxy group was protected with a stable group. Purple colored impurities, one of which has been identified as azulene 45, were seen in both coupling reactions using C-TMS-alkynes such as 36 and 40d (Scheme 4.9). The azulene was presumably formed through the dimerization of acetylenes... 

Photolysis of the triazepine products produces 2,2-dimethylpropanenitrile and the corresponding pyrazole in quantitative yield <1997BSF927>. Reaction of sydnone 89 with fulvene 91 proceeds by [ji4s + jt6s]-cycloaddition followed by spontaneous loss of carbon dioxide and a molecule of dimethylamine or acetic acid from the pseudo-azulene , cyclopentaMpyridazine 92 (Equation 9) <1996CC1011, 1997T9921>. 

Compound R Conditions of reaction Yields (%) (related to the turnover of the azulene) 28 29 Reference... 

The electrochemical reduction of azulene with carbon, platinum, lead or zinc cathode does not give any product, whereas that with magnesium electrode yields a dimeric compound as the only reduction product, though the dimeric compound is easily transformed to the corresponding monomeric compound by a mild oxidation as shown in equation 2825. 

This procedure illustrates a simple and general method for preparing azulenes. It is far more convenient and proceeds in much better yield than previous syntheses of azulenes involving... 

The reaction of salt 369 with acetic anhydride affords a cyclized product characterized as 2-methyl-1,3,3a,9-tetra-zacyclopentant[ ]azulene 370 (Scheme 38) <1999J(P1)1339>. The reaction of l,2-diamino-l,3-diazaazulenium compound 369 with diethyl ethoxymethylenedicarboxylate (DEEM) provides a complex reaction mixture, one of the isolated products being compound 21, which is isolated in 29% yield when the reaction is carried out in ethanol, but in 47% yield, when acetonitrile is used as solvent (Scheme 38) <1999J(P1)1339>. 

The dication 212+ composed of two methylium units connected to a p-phenylene spacer would be a candidate for new Wurster type violene-cyanine hybrid (Figure 12) (15). The reaction of four molar amounts of azulene 6b with terephthalaldehyde yielded the hydro precursor. Synthesis of the dication 212+ was accomplished by hydride abstraction with DDQ in almost quantitative yield. The dication 212+ was expected to show destabilization, but instead it exhibited high thermodynamic stability just like the corresponding monocation 3b+. 

The cyclization of (l-azaazulen-2-yl)hydrazinomethylenemalonates (1409) in boiling te/7-butylbenzene for 30-40 min afforded l,2,5a-triaza-cyclohept[u]azulen-5-ones (1410) in 74-93% yields (88BCJ1440). Whereas the methyl derivative of 1409 (R = Me) could be cyclized in 56% yield in chloroform by treatment with silica gel at room temperature for 7 days, the ethoxycarbonyl derivative (1409, R = COOEt) could not. 

Nair and coworkers have described the [8 + 2] cycloaddition reactions of 2H-cyclohep-ta[fr]furan-2-ones such as 521 in several reports311. The reactions of 521 with alkenes yield azulene derivatives upon extrusion of carbon dioxide. Table 30 summarizes the results of the reactions between 521 and some 6,6-disubstituted fulvenes 522 (equation 151)311b. In the case of 6,6-dialkyl fulvenes 522a-c, the [8 + 2] cycloadducts 523 were the major adducts obtained, the Diels-Alder adducts 524 only being formed in trace amounts. 

In the contrast to the SiCaT reaction of triynes vide supra), when an enediyne has an olefin at the terminal position a novel silicon-initiated carbonylative carbotricyclization (CO-SiCaT) reaction takes place, incorporating CO into the product [52], As Scheme 7.24 indicates, the reaction of dodec-ll-ene-l,6-diynes 82 catalyzed by Rh(acac)(CO)2 under 1 atm. CO affords the corresponding cyclopenta[e]azulenes 83 in good to excellent yield. 

Arylbenzotriazoles (797) are prepared via 2-nitro- and 2-amino-diphenylamines (Scheme 161). The 2-nitrodiphenylamines (796) are prepared from the appropriate aniline by reaction with 2-fluoronitrobenzene in the presence of KF <808215,85JCS(Pl)2725>. Azo-coupling of 2-amino-1-cyano-azulene (798) with p-tolyldiazonium chloride gives (799) (Scheme 162). Catalytic reduction of (799) quantitatively yields the diamino derivative (800), which on diazotization affords 9-cyano-azuleno[l,2-J]triazole (801) in 77% yield <85TL335>. 

Kato et al. (151,152) explored the chemistry of 2-ferf-butylMvenes with isomiinchnones, as well as with several other mesoionic compounds, in a novel approach to pseudo-hetero-azulenes. Thus, isomtinchnone 51a, generated as before in situ from A-benzoylphenylglyoxyanilide 253 with triethylphosphite, reacts with 2-ferf-butyl-6-(dimethylamino)fulvene to give the [47i+6ti] adduct diphenylcyclo-penta[c]pyran in low yield. Likewise, reaction of 51a with dimethylfulvene gave a mixture of two adducts, one of which arises from a [47i+2ti] cycloaddition. 

In contrast to the reactivity of 6-dodecene-1,11-diynes, rhodium-catalyzed reaction of l-dodecene-6,11-diynes with silane led not to cascade cyclization/hydrosilylation but rather to carbonylative tricyclization. For example, reaction of 87 [X = G(G02Me)2] and dimethylphenylsilane catalyzed by Rh(acac)(GO)2 in THE at room temperature under GO gave the cyclopenta[e]azulene 88 in 92% yield as the exclusive product (Scheme 22). Although the protocol was... 

In the reaction of azulene with [Ru(CO)4SiMe3]2, two other products were isolated, namely Ru2(CO)2(C1oHg) (10% yield) and Ru2(SiMe3)2 (CO)4(C10Hg) (5% yield). The probable structure of the diruthenium compound 94) is... 

The photodissociation of aromatic molecules does not always take place at the weakest bond. It has been reported that in a chlorobenzene, substituted with an aliphatic chain which holds a far-away Br atom, dissociation occurs at the aromatic C-Cl bond rather than at the much weaker aliphatic C-Br bond (Figure 4.30). This is not easily understood on the basis of a simple picture of the crossing to a dissociative state, and it is probable that the reaction takes place in the tt-tt Si excited state which is localized on the aromatic system. There are indeed cases in which the dissociation is so fast (< 10-12 s) that it competes efficiently with internal conversion. 1-Chloromethyl-Np provides a clear example of this behaviour, its fluorescence quantum yield being much smaller when excitation populates S2 than when it reaches Figure 4.31 shows a comparison of the fluorescence excitation spectrum and the absorption spectrum of this compound. This is one of the few well-documented examples of an upper excited state reaction of an organic molecule which has a normal pattern of energy levels (e.g. unlike azulene or thioketones). This unusual behaviour is related of course to the extremely fast dissociation, within a single vibration very probably. We must now... 

The reaction of carbenoids with aromatic systems was first reported by Buchner and coworkers in the 1890s.6 The reaction offers a direct entry to cycloheptatrienes and has been used to synthesize tropones, tropolones and azulenes.6 Neither the thermal nor copper-catalyzed reactions, however, proceed in good yield. The problems associated with these transformations were clearly demonstrated in a recent reexamination of die thermal decomposition of ethyl diazoacetate in excess anisole (137).129 A careful analysis of the reaction mixture revealed the presence of seven components (138-144) in 34% overall yield (Scheme 29). The cycloheptatrienes (138M142) were considered to be formed by cyclopropanation followed by electrocyclic ring opening of the resulting norcaradienes. A mixture of products arose because the cyclopropanation was not regioselective and, also, the initially formed cycloheptatrienes were labile under the reaction conditions. 

Decomposition of l-diazo-4-arylbutan-2-ones offers a direct entry to bicyclo[5.3.0]decatrienones and the approach has been extensively used by Scott and coworkers to synthesize substituted azulenes.137 Respectable yields were obtained with copper catalysis,137 but a more recent study24 showed that rho-dium(ll) acetate was much more effective, generating bicyclo[5.3.0]decatrienones (154) under mild conditions in excess of 90% yield (Scheme 34). The cycloheptatrienes (154) were acid labile and on treatment with TFA rearranged cleanly to 2-tetralones (155), presumably via norcaradiene intermediates (156). Substituents on the aromatic ring exerted considerable effect on the course of the reaction. With m-methoxy-substituted systems the 2-tetralone was directly formed. Thus, it appeared that rearrangement of (156) to (154) was kinetically favored, but under acidic conditions or with appropriate functionality, equilibration to the 2-tetralone (155) occurred. 

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