3- tropolone, reaction with

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. - ... 

M(OR)5 reacts with /3-diketones, thio-/3-diketones, /3-keto esters and /3-hydroxy esters (Table 9). Only three of the five OR groups could be replaced by these bidentate monoanionic dTbH ligands. Surprisingly, the reaction of tropolone (HT) with Nb(OEt)5 was reported to yield [Nb(OEt)T4], whose structure remains unknown. 

Eschenmoser s pyrone 38 on treatment with cyclopropenone ketal 39 in refluxing benzene afforded lactone 40 (73%). Lactone 40 on hydrolysis with acetic acid at 100°C afforded, after deprotection and decarboxylation, tropone 37 (70%). Introduction of the tropolonic hydroxyl group was achieved with hydrazine hydrate in ethanol, to give a mixture of deacetyl-colchiceinamides 41 (53%) and 42 (37%), followed by reaction with ethano-lic potassium hydroxide, which afforded tropolones 43 and 44, respectively. Tropolone 43 was converted to 44 which, therefore, became the major reaction product. Methylation of 44 gave a mixture of enol ether 18 and 45 which were separated by chromatography. 

In the presence of a Mannich base, hydroxymethyl derivatives 268 may behave, in turn, as alcoholic reagents, thus affording amino group replacement with formation of the symmetrical ether 269 (R = R —CH ). Indeed, alcohols and phenols allow the synthesis of ethers 269, starting from phenolic Mannich bases as well as from the methiodides of aminomethylfcrrocenes, by reaction with alkoxide or phenoxide. Good results have been obtained with a thioporphirine Mannich base and zinc acetate. Esters 270 (Fig. 102) can be synthesized from various Mannich bases such as those derived from tropolones or purines, which are converted into acetoxymethyl... 

Diek-AUer reactions. The Diels-Alder reaction of cyclopropene with cyclopcnt-adicne has already been mentioned (I, 1040). In fact, cyclopropene is one of the most reactive dienophiles. It reacts with tropone (1) in methylene chloride at 0° to give the 1,4-addition product (2). Similarly, reaction with tropolone (3) affords the adduct (4). 

This reaction is the first example of a Diels-Alder reaction with tropolone. The emh selectivity seems to be a general property of cyclopropene. ... 

Ethoxy-2,3-diphenylcyclopropenylium ion 16 was also used for the synthesis of quinone forms of heptatriafulvalenes via reactions with a-tropolones (2-hydroxycyclohepta-2,4,6-tri-enones). ... 

In an analogous manner 4-phenyl-1,3-dithiolyIium perchlorate (80) afforded, upon reaction with tropolones, the 2-(4-hydroxy-5-oxo-l,3,5-cycloheptatrien-yl)-4-phenyl-l,3-dithioles (81), which can be transformed into (82) (Scheme 18) <77CL1505>. 

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. 

Reaction with tropone and tropolone.5 The reagent reacts with tropone to give the highly reactive ketone (1) the following mechanism is proposed ... 

The reaction with tropolone is accompanied by O-alkylation to give the ketone (2) in 54% yield. 

Rearrangement to the proper orientation of the tropolone system was accomplished by reaction with p-toluenesulfonic acid in pyridine and then treatment with ammonia to form LXXIV, whose UV-spectrum was identical with that of colchicinamide. Hydrolysis converted LXXIV to desacetamidocolchiceine (LXII), identical with the authentic degradation product (mixed melting point and spectra). 

Didehydrotropone, prepared by oxidation of l-amino[4,5-d]-1,2,3-triazole with lead tetraacetate, undergoes cycloaddition reactions with pyridazine M-oxides <94H(38)957>. Loss of nitrogen by the cycloadduct results in the formation of tropono[4,5-b]oxepines (Scheme 10). The electron deficient nature of the tropolone ring precludes the formation of [4 + 2]jt cycloaddition products by the oxepine ring, in contrast to the reactivity of benz[l>]oxepines. 

Chlorine also reacts readily with tropolone by substitution, entering the 5-position more readily than does bromine [291,293]. Trichlorotropolones undergo addition reactions with more chlorine to give adducts which rearrange with formation of a six-membered ring [294]... 

Itydroxymethylation and aminomethylation of tropolones can be effected by-reaction with, respectively, formaldehyde and alkali [308], and formaldehyde and morpholine [309]. 3,5,7-Trisubstituted products are readily obtained. 

Bromotropolone gives a similar mixture of 3- and 4-methoxy-tropolones [316]. The intermediate acetylene has been trapped by reaction with diphenylisobenzofuran or azide anion [316]... 

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