Methyl-chromone 3-hydroxy-6-

The initial compound (9) was prepared by stirring 1,3,5 trimethoxybenzene with 1 -methyl-4-piperidone in glacial acetic acid. The tram alcohol (10) was obtained by hydration of the double bond and the corresponding cis compound (11) then made via the ketone by oxidation then reduction. Treatment with acetic anhydride and an acid catalyst such as boron trifluoride etherate gave (12). Treatment of this compound at room temperature with ethyl benzoate in the presence of sodium metal produced the diketone (13) which was cyclised to (14) by the addition of mineral acid. Final demethoxylation of the chromone hydroxy groups with pyridine hydrochloride was carried out for several hours at 180°. 

A Russian team [128] studied the relationship between chemical constitution and colour in a series of chromone-2-carboxylic acid amides (37). When R = H, the compound is colourless but as the substituent is varied through methyl, methoxy, hydroxy to diethylamino, the colour changes through greenish yellow to red. Similar substituents in the meta position exert comparatively little effect. When R = SO3H, the anilide is greenish yellow in the solid state but colourless in solution its crystalline sodium salt is colourless. Since A-4-hydroxyphenyl-A-methylchromone-2-carboxamide (38) is colourless [128], it was suggested that the colour of the anilides was related to their ability to enolize. 

Chromone, 5-hydroxy-2-methyl-biosynthesis, 3, 876 Chromone, 6-hydroxy-2-methyl-reactions... 

Chromone, 7-hydroxy-2-methyl-bromination, 3, 707 Chromone, 3-hydroxymethylene-synthesis, 3, 821... 

Chromone-5-carboxylic acid, 7-hydroxy-2-methyl-decarboxylation, 3, 711 Chromonecarboxylic acids decarboxylation, 3, 710 Chromone-2-carboxylic acids esters... 

Dihydro- 7 -hydroxy-2S, 3 R -dimethyl-2-[4-methyl-5-(4-methyl-2-furyl) -3 (E), 7 -pentenyl]-furo[2,3-B]chromone ... 

Bei der analogen Nitrierung von 7-Hydroxy-4-methyl-2H-chromon erhalt man zu 73% 7-Hydroxy-4-methyl-3,6,8-trinitro-2H-chromon [Schmp. 216 217 (Aceton)]1 ... 

Pyrimidin 5-(2-Hydroxy-benzoyl)-2-methyl- E9b/2, 170f. (3-CHO 4H-chromon + Acetamidin) Quinazolin 2-(2-Furyl)-4-methyl- -3-oxid E9b/2, 18 [2-(NH-CO-Het) —Ar— 1-CR = N —OH/H+] Quinolin 3-Amino-4-hydroxy-2-oxo-1 -(2-propinyl)-l, 2-dihydro-E15/2, 1251 (1,3-Oxazol-Spalt.)... 

Amino-5-(2-hydroxy-benzoyl)-4-methyl- E9b/2, 170f. [3-(CO —NH2) —4H-chromon + Guanidin]... 

CH3 4,9 -Dimethoxy -5-oxo - 7-methyl-2,3,6,7-tetra-hydro -5H- (furo [g]-chromen) 56% d.Th. och3 och3 7-Hydroxy-5,8 -dimethoxy 2 -methyl-6-dthyl-4H -chromon 39% d.Th. 

Elimination of the ring C as a hydroquinone derivative with the formation of chromones from rings A and B. This type of fission is most prominent with flavonoids whose A ring hydroxy groups are blocked, e.g., by methylation. 

Wagner H, El-Sayyad SM, Seligmann O, Chari VM 1978 Chemical consituents of Cassia siamea. I. 2-methyl-5-acetonyl-7-hydroxy-chromone (cassiachromone). Planta Med 33 259-261... 

Also obtained by hydrolysis of 6-hydroxy-2-methyl-8-nitro-chromone with 10% aqueous sodium hydroxide [1831]. 

If 2-hydroxyacetophenone analogues such as 3-acetyl-4,6-dimethyl-2-pyridone and 4-acetyl-5-hydroxy-3-methyl-l-phenylpyrazole are used as the methylene component in the condensation with R COaEt in the presence of LiH in THE or dioxane, the reaction gives the corresponding R -containing p-diketones 132 and 134, whose dehydration under the action of concentrated H2SO4 affords 8-aza-2-(polyfluoroaIkyl) chromones 133 [58] and 6-(polyfluoroalkyl)-3-methyl-l-phenylpyrano[2,3-c] pyrazol-4(17/)-ones 135 [59] (Scheme 41). 

These prodncts are formed through nucleophiUc attack followed by Claisen condensation (intermediate A), intramolecular cyclization and dehydration (intermediate B), and then by aromatization (after hydrolysis and decarboxylation) through involvement of the phenolic hydroxy group. At the same time, chromone 130a reacts with cyanoacetamide, A-methyl cyanoacetamide, and cyanoacetohydrazide in the presence of sodium ethoxide, affording 2-pyridones 212 in good yields [104] (Scheme 68). 

Derivatives of 4-hydroxy-2-(trifluoromethyl)-4//-chromene 221 were obtained via condensation of salicylaldehydes with methyl ( -2-bromo-4,4,4-trifluoro-2-butenoate [111] or methyl 2-perfluoroaIkynoates [112], Treatment of 221 with Sarrett reagent in CH2CI2 generated chromones 220 in high yields [111]... 

Reactions of chromones 230 with acetoacetamide and ethyl acetoacetate in ethanol in the presence of ammonium acetate proceed at the C-2 atom of the chro-mone system with pyrone ring-opening and subsequent cycUzation to 252. Similar reaction with p-aminocrotononitrile gave 5-hydroxy-2-methyl-5-(polylluoroalkyl)-5ff-chromeno[4,3- ]pyridine-3-carbonitriles (253a) [129]. Three-component reaction between chromones 230, dimedone, and AcONH, is accompanied by detrifluoroacetylation and leads to 254 in low yields [130] (Schane 82). 

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