2-Carboxylic chromone acid chloride

Hydrochloric acid 2-Carboxylic chromone acid chloride... 

The amine is then used to introduce a nitrile by diazotization followed by treatment of the diazonium salt with cuprous cyanide (180) the methyl ether is then cleaved by means of aluminum chloride. Treatment of the phenolic ketone 181 with benzoyl chloride and sodium benzoate serves to build up the chromone ring (182). The nitrile is next hydrolyzed to the acid with sulfuric acid. Esterification of the carboxyl as—its acid chloride—with N-(2-hydroxyethyl)piperi-... 

Nitration of hydroxypropiophenone (7-1) followed by conversion of the phenol to its methyl ether by means of methyl iodide provides the intermediate (7-2) the nitro group is then reduced to the corresponding amine (7-3) by catalytic reduction. The newly introduced amine is then replaced by a nitrile group by successive conversion to the diazonium salt by means of nitrous acid followed by treatment with cuprous cyanide (7-4). Reaction with aluminum chloride removes the methyl ether to afford the ortho acylphenol (7-5). This is converted to the chromone (7-6) as above by reaction with benzoyl chloride and sodium benzoate. The nitrile is next hydrolyzed to the carboxylic acid (7-7) by means of sulfuric acid. The acid is then converted to its acid chloride by means of thionyl chloride and that treated with 2-(A -piperidyl)ethanol (7-8). There is thus obtained flavoxate (7-9) [8], a muscle relaxant whose name reflects its flavone nucleus. 

The reaction between the acid chloride of chromone-2-carboxylic acid and ethyl ethoxymagnesioacetoacetate probably leads to the expected fi-diketone which enolizes and cyclizes spontaneously to spirofuranone(52).127 A different approach was made by Hungarian workers in their synthesis of tachrosin (53), an unusual kind of flavone isolated from Tephrosia poly-stachyoides and one of the earliest natural furanones to be isolated. They subjected an unsaturated ketone (Scheme 32) to oxidative rearrangement by thallium(III) salts, a reaction well known in chalcone chemistry, and eliminated methanol from the product to obtain the necessary starting material.128... 

The acid chlorides of several chromone-2-carboxylic acids have been used in the Freidel-Crafts reaction to prepare 2-aroyl-chromones which were pharmacologically active.Decarboxylation of a heterocyclic acid is often a facile reaction but removal of an aldehyde group is unusual. Chromone-3-carboxaldehyde (156) has been decarbonylated by heating with piperidine to give the acrylophenone (157), which cyclized again, with loss of piperidine and one carbon atom. ... 

Chromone-2-carbaldehyde, 3-methyl-synthesis, 3, 709 Chromonecarbaldehydes Knoevenagel condensation, 3, 711 Chromone-3-carbaldehydes mass spectra, 3, 615 oxidation, 3, 709 reactions, 3, 712 Schiff bases, 3, 712 synthesis, 3, 821 Chromone-2-carbonyl chloride Grignard reaction, 3, 711 Chromonecarboxamide, N-tetrazolyl-antiallergic activity, 3, 707 Chromone-2-carboxylic acid, 3-chloro-ethyl ester... 

The reaction of chromone-2-carboxylic acid with thionyl chloride or phosphorus halides gives the trihalide (400). This compound readily loses one of its geminal chlorine atoms and with water, for example, affords 4-chlorocoumarin through the simultaneous loss of carbon monoxide (Scheme 131) (63JGU1806). 

Similar results have been obtained for some reactions between phosphite triesters and the chlorides from heterocyclic carboxylic acids. The first of these to be reported were for the pyridinylcarbonyl chlorides. Here, 270 from 2-pyridinylcarbonyl chloride, and 271 from the 3- and 4-pyridinyl chlorides, were obtained presumably via the betaines Similarly, the acylphosphonate 274, from 273, reacted with more trialkyl phosphite (R = Me or Et), possibly via structures 275 and 276 (together with, in the latter case, the geometrically isomeric form) to give the isolated products, 277 and 278 (again as geometric isomers) With 4,4-dichloro-4//-benzopyran-2-ylcarbonyl chloride, a similar mechanism was postulated but with the loss of one chlorine atom (as in 279) to restore electron redistribution within the chromone system" the E structure was confirmed by X-ray crys-tallography ... 

Chromone-3-carboxylic acid esters (34) containing four fluorine atoms on the benzene ring were synthesised by Vorozhtsov, Barkhash, Prudchenko and Khomenko [122, 123] from pentafluorobenzoyl chloride and ethyl acetoacetate in the presence of magnesium ethoxide. During cyclisation, an o-fluorine atom is eliminated the tetrafluorochromone was isolated (in high... 

Deactivation of C-3 by the carboxyl group at C-2 prevents attack by electrophiles, for example, the Mannich reaction results in substitution at C-3 in many chromones [16] but not with chromone-2-carboxylic acid or ester. Radical (homolytic) chlorination of the ester or nitrile using sulphuryl chloride and a trace of benzoyl peroxide gives the 3-chloro derivative (84) [57, 149, 167]. 

Chlorocoumarin may be prepared by the reaction of chromone-2-carboxylic acid with thionyl chloride [169] or oxalyl chloride [55]. 4,4-Dichlorochromen-2-carbonyl chloride which is formed first, reacts with water to give a 91 per cent yield of 4-chlorocoumarin (92) with simultaneous release of carbon monoxide [161]. 

The reaction of o-fluorobenzoyl chloride with p-ketoesters in the presence of NaH has been proposed as a method for the synthesis of 2-methylchromone-3-carboxyUc acid and its esters. In particular, this reaction proved to be suitable for the preparation of ethyl 2-(trifluoromethyl)chromone-3-carboxylate (220) [110] (Scheme 71). 

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