Tropolone derivatives

Sekiya and his collaborators [44—48] found spectral doublets in the Sj-Sq excitation and dispersed fluorescence spectra of jet-cooled halotropolones that are modifications of the basic coherent tunneling splittings observed for TRN(OH) and TRN(OD). The symmetrical chlorotropolones shoived enhancements of the spec- 

L This 14q1 transition is only tentatively assigned. 

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The present procedure, based on the last method, is relatively simple and uses inexpensive starting materials. Step A exemplifies the 2 + 2 cycloaddition of dichloroketene to an olefin, " and the specific cycloadduct obtained has proved to be a useful intermediate in other syntheses. Step B has been the subject of several mechanistic studies, and its yield has been greatly improved by the isolation technique described above. This synthesis has also been extended to the preparation of various tropolone derivatives. " ... 

A variety of derivatives of bis-[Bi(tr)2X, X = Cl or N03], tris-(Bitr3), and tetra-([Bi(tr)4X][Na]) tropolonate complexes of bismuth (178, 179) have been prepared and spectroscopically characterized (176, 177, 180). Solid-state structures for examples of bis-(tropolonate) derivatives confirm the chelate interaction (171) and in the case of the nitrate derivative, reveal intermolecular alkoxide-bismuth [Bi-0 2.688 and 2.666 A] dimer contacts 52, which are slightly longer than the chelate bonds [Bi-0 2.130-2.323 A],... 

Similar irradiation of the 1 1 complex of tropolone ether 10b and host compound 8 led to photoproducts 11b (100% ee) and 12b (72% ee) in 12 and 14% yields, respectively. The authors interpreted these reactions as follows disrotatory electrocyclic closure of tropolone derivative 10 to afford photoproduct 11 in the inclusion crystals occurs in only one direction owing to the steric hindrance of host 8. This interpretation appeared to be reasonable based on an examination of the X-ray crystal structure study of the inclusion complex [18]. Formation of keto-ester 12 takes place by a more complex mechanism... 

Tropolone has been made from 1,2-cycloheptanedione by bromination and reduction, and by reaction with N-bromosuccinimide from cyclo-heptanone by bromination, hydrolysis, and reduction from diethyl pimelate by acyloin condensation and bromination from cyclo-heptatriene by permanganate oxidation from 3,5-dihydroxybenzoic acid by a multistep synthesis from 2,3-dimethoxybenzoic acid by a multistep synthesis from tropone by chlorination and hydrolysis, by amination with hydrazine and hydrolysis, or by photooxidation followed by reduction with thiourea from cyclopentadiene and tetra-fluoroethylene and from cyclopentadiene and dichloroketene. - The present procedure, based on the last method, is relatively simple and uses inexpensive starting materials. Step A exemplifies the 2 + 2 cycloaddition of dichloroketene to an olefin, " and the specific oycloadduot obtained has proved to be a useful intermediate in other syntheses. " Step B has been the subject of several mechanistic studies, " and its yield has been greatly improved by the isolation technique described above. This synthesis has also been extended to the preparation of various tropolone derivatives. - " ... 

Most pyrogallol derivatives did not precipitate either (Table III). A small precipitation occurred with pyrogallol (which may be considered as a hydroxyresorcinol) and it reacts with vanillin/HCl also (7). However, any additional substitution eliminates this reactivity, e.g., gallic acid (Table IV). Purpurogallin did precipitate with formaldehyde. It is not very soluble in the reaction mixture, and it is a tropolone. Structures of this type might interfere, but in tea and probably in wine the known tropolone derivatives are flavonoids (I, 25). 

Colchicine is an important naturally occurring tropolone derivative. It is isolated from the autumn crocus and is used in medicine for the treatment of gout. It also has an effect on cell division and is used in plant genetic studies to cause doubling of chromosomes. The structure has been confirmed by total synthesis. 

Joy, A., Kaanumalle, L.S. and Ramamurthy, V. (2005) Role of cations and confinement in asymmetric photochemistry enantio- and diastereo-selective photocydization of tropolone derivatives within zeolites. Organic Biomolecular Chemistry, 3, 3045-3053. 

Hinokitiol is a tropolone type natural compound isolated from the wood of Chymacyparis taiwanesis. The compound has been utilized as a natural antimicrobial agent in hair tonics, toothpastes, cosmetics and food supplements. Hinokitiol was evaluated on five different arachidonic acid metabolic pathways for the mechanism of action of anti-inflammatory effects. It has been found to be a potent inhibitor with IC50 values of 0.1 pM against platelet-type 12-LOX and 50 pM against leukocyte-type 12-LOX. It also inhibited soybean 5-LOX enzyme (IC50 = 17 pM). However, hinokitiol had almost no effects on COX-1 and COX-2 enzymes. Similar inhibition profiles were also observed on synthetic tropolone derivatives [168]. 

Also, interesting 7,10-dithiasesquifulvalene-l, 2-quinone derivatives (204) can be obtained by condensation of 2-methylthio-l,3-dithiolylium iodide with a-tropolone derivatives (203) (81CL805). With j8-tropolone (205) and 1,3-dithiolylium iodide (195) in the presence of pyridine the reaction proceeds with formation of the 7,10-dithiasesquifulvalene-1,6-quinone (206) (77CL287). 

Entsprechendes soli auch fiir Tropolon-Derivate gelten 104>. (S. jedoch 164>). Der Fall eines vollig regularen Siebenringes diirfte somit am ideal-sten im Tropylium-Ion 10t verwirklicht sein. 

The most successful supramolecular photochirogenesis with chirally modifiea zeolites is the enantiodifferentiating photocyclization of tropolone derivatives in[ zeolites modified with (— )-ephedrine or (— )-norephedrine, giving bicyclo[3.2.0J heptadienes in high ees. It is interesting to compare this result with the highlj ... 

As briefly mentioned above, Takeshita et al. reported the first enantiodifferentiat-ing photoisomerization of tropolone derivatives to the optically active bicyclo[3,-2.0]heptadienones in 1980 [99], but the product ee and detailed chiral discrimination mechanism have not been determined until recently. Ramamurthy and coworkers reinvestigated the photobehavior of tropolone alkyl ethers in a-, (3-, and y-CDx cavities [102]. 

Owing to Michael J. S. Dewar s brilliant experimental and theoretical contributions in the field of tropolone derivatives, it was believed that tropone and the pair of isomeric a- and y-pyrones had considerable aromaticity, with the zwitterionic resonance formula of the carbonyl playing the role of a Z-type atom. Soon, however, it was shown that the extent of aromaticity was very low, and it increased only after combining with electrophiles, for example on protonation or alkylation (such as the formation of methiodides) (69JA5286, 72T5299, 030BC3410). 

Diketonates include [Bi(ACAC)3]," and [Bi(dpm)3]." Tropolone derivatives have attracted interest as anti-Helicobacter pylori agents. Various types are known, including [Bi2(N03)2(trop)4] (tropH = tropolone) which is a dimer (Figure 64), [Bi(trop)2(H20)]N03, [BiPh(trop)2], and [Bi(trop)4] all of which are essentially monomers. ... 

Finally, the ability of phosgene to engage in dichlorodeoxygenation extends to tropolone derivatives, such as 7H-benzocyclohepten-7-one [664] ... 

Syntheses of tropolone derivatives (similar to the transformation 12 13), based on sequential... 

Diols, e.g. 78, may be converted in quantitative yield to y-tropolone derivatives in a similar two-step sequence. 

Triacetic acid lactone (1) is one of the simplest polyketides, and its formation from acetyl-CoA and malonyl-CoA has been proved (68JBC5471). Biogenetic formation of triacetic acid lactone has been considered a derailment from fatty acid biosynthesis promoted by the absence of the reductant NADPH (69MII). Pyrone 1 has been isolated from microorganisms (67JA676) and is transformed into tropolone derivatives by Penicillium stipitatum (67JA681). 

Triphenylbismuthonium 2-oxoalkylides readily couple with a-dicarbonyl compounds in several different reaction modes [96CC2697, 98CC1359J. When treated with ethyl pyruvate, the epoxidation proceeds to form 2,3-difunctionalized oxiranes. The reaction with benzils gives O-aroylenolates derived from 1,3-diketones, while treatment with o-quinones affords 2-acyl-1,3-tropolone derivatives. These reaction modes are unprecedented in the ylide chemistry. 

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