Tropolone, acidity

Carboxylic acids —CO2H All types 3000-2500 as in tropolones OH stretching a characteristic group of small... 

In this case the parameters C and Q are of order of unity, and therefore they correspond to the intermediate situation between the sudden and adiabatic tunneling regimes. Examples are mal-onaldehyde, tropolon and its derivatives, and the hydrogen-oxalate anion discussed above. For intermolecular transfer, corresponding to a weak hydrogen bond, the parameters C, Q and b are typically much smaller than unity, and the sudden approximation is valid. In particular, carbonic acids fulfill this condition, as was illustrated by Makri and Miller [1989]. 

Tropolone has been made from 1,2-cycloheptanedione by bromination and reduction, and by reaction with A -bromosuccinimide from cyolo-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. - ... 

Tlie synthesis concludes by the route pioneered by Eschenmoser. Itromination of 47 proceeds at the position a to the tropolone I ing to give 48. Displacement of halogen by ammonia followed by liase hydrolysis of the tropolone methyl ether gives trimethyl-lolchicinic acid. Acetylation of the amine followed by reesteri-... 

In this method the sample (1—20g) is weighed in a flask, internal standard is added, and the sample acidified with hydrochloric acid to pH2-3. When the evolution of gas has ceased, the slurry is extracted with three portions (10, 5 and 5mL) of a 0.25% ethereal Tropolone solution. After being shaken vigorously and centrifuged, the organic phases are combined, filtered through anhydrous calcium chloride, and reduced in volume to about 2mL at room temperature by a rotary evaporator. The extract is then ready for derivatization. 

The tropolone alkaloid of Liliaceae species, colchicine, is transformed by acetylation, alkaline cyclization, and dehydration into the tetracyclic pyrrolotropone acetyl anhydrocolchicine [77TL2977 83AX(C)1709]. When the dicarboxylic acid anhydride groups of puberulonic and stipitatonic acids (metabolites of Penicillium species) condense with o-phenylenediamine, another tetracyclic pyrrolotropone structure is formed (51JCS1139 59JCS2847). 

General methods for the preparation of niobium(v) and tantalum(v) complexes have been discussed and better synthetic routes to some known compounds have been described. [Nb(bpha) Cl], [Ta(bpha) Cl], and [NbO(t)3] (where bpha and t are the anions of benzoylphenylhydroxylamine and tropolone, respectively) have been prepared for the first time. NbClj or TaClj in methanol react with Hbpha to form the [M(bpha)4Cl] complexes. An aqueous solution of niobiumfv) which contains tartaric acid to prevent condensation of the hydrolysed metal species affords [NbO(t)3] with tropolone." " ... 

The complexes [Ru(bpy)2L]+ (HL = acetylacetone, trifluoroacetylacetone, hexafluoroacetylace-tone, tropolone or dibenzoylmethane) have been prepared and characterized they act as catalysts for the oxidation of alcohols, 3,5-di-tert-butylcatechol and alkanes in the presence of appropriate co-oxidants." Perchlorate salts of [Os(bpy)2L] in which HL = salicylaldehyde, 2-hydroxyaceto-phenone or 2-hydroxynaphthaldehyde, are formed from reactions of [Os(bpy)2Br2] with HL. The structure of the salicylaldehyde derivative has been determined. Chemical and electrochemical oxidations of [Os(bpy)2L]" yield the corresponding low-spin Os species from which [Os(bpy)2L]+ can be regenerated." " [Ru(bpy)2L]" (HL = salicylic acid) has been prepared and structurally characterized as the tetrahydrate. Absorptions at 590 nm, 400 nm, and 290 nm in the electronic spectrum have been assigned to Ru bpy CT transitions electrochemical oxidations of the complex have been investigated." ... 

B. Tropolone. In a 1-1., three-necked, round-bottomed flask equipped with a mechanical stirrer, addition funnel, and reflux condenser are placed 500 ml. of glacial acetic acid and then, cautiously, 100 g. of sodium hydroxide pellets. After the pellets have dissolved, 100 g. of 7,7-dichlorobicyclo[3.2.0]hept-2-en-6-one is added and the solution is maintained at reflux under nitrogen for 8 hours. Concentrated hydrochloric acid is then added until the mixture is about pH 1 approximately 126 ml. of acid is required. After the addition of 11. of benzene, the mixture is filtered and the solid sodium chloride is washed with three 100-ml. portions of benzene. The two phases of the filtrate are separated and the aqueous phase is transferred to a 1-1. continuous extractor (Note 8) which is stirred magnetically. The combined benzene phase is transferred to a 2-1. pot connected to the extractor and the aqueous phase is extracted for 13 hours. Following distillation of the benzene, the remaining orange liquid is distilled under reduced pressure... 

Numerous reactions of the betaines 86 with olefinic 1,3-dipolarophiles have been reported. lV-Methylpyridinium-3-olate (111) with electron-deficient olefins gives the adducts 112. - Alkynes give similar adducts (110) These adducts (110 and 112) are useful intermediates for tropolone synthesis. Quaternization to methiodides (113, 115) and treatment with base gives dimethylaminotropones (114) which are hydrolyzed to tropolones (116). Good syntheses of stipitatic acid (116 R = COjH, R = OH) and hinokitiol (116 R = H, R = CHMe ) have been achieved by this route (Scheme 5). Similar transformations have been achieved using the N-phenyl betaine 86 (R = Ph, R = H) which is more reactive but whose adducts are difficult to quaternize. A difference is observed when benzyne is... 

The result of the reaction of sulfur tetrafluoride with alcohols strongly depends on the structure of the alcohol. Simple aliphatic alcohols, such as methanol, ethanol and propan-2-ol, give alkyl ethers as the main product with only small amounts of fluoroalkanes.41 42 Yields of fluorinated products increase with increasing acidity of the hydroxy group and, in general, the reaction is only synthetically useful with alcohols equally or more acidic than tropolone (p K, = 6.42). 

MC15 when allowed to react with acidic aqueous solutions of tropolone (HT) gave the tetrakis(tropolonate) cations [MT4]+. Hydrolysis of the niobium derivative afforded [NbOT3], an oxygen-labeling experiment established that the oxo atom is abstracted from the displaced tropolone molecule. 

A-Benzoylphenylhydroxylamine (BPHA) reacts with Nb20 in bioling acidic aqueous solutions to yield a monomeric seven-coordinated niobium compound [NbO(BPHA)3]. The hydroxylamine ligand could be displaced by tropolone or 8-quinolinol, and the ratedetermining step was shown to be associative (equation 38).427 Oxoniobium and tantalum(V) 8-quinolinolates have also been reported. The optimal conditions for the formation and extraction of the [Nb0(C6H402)3]3 ion formed in the niobium(V)-pyrocatechol system, have been investigated.428... 

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