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6-Aryl-4-hydroxy-2-pyrones

The retrosynthetic analysis of arisugacin is shown in Scheme 12.2. It is clear to us that this formal [3+3] cycloaddition method could be invaluable to achieve a practical total synthesis of arisugacin A 6 or other family members and their analogs [20]. Specifically, the reaction of a,(3-unsaturated iminium salts 13 with 6-aryl-4-hydroxy-2-pyrones 14 should provide a facile access to the advanced pentacyclic intermediate 12. [Pg.284]

Structurally related to the triarylmethanes is the xanthene chromogen (1.30), in which two of the aryl nuclei are linked by an oxygen atom to form a pyrone ring. Similar terminal groupings (amino, hydroxy, or both) are usually present. Xanthene dyes have mainly... [Pg.12]

The 4-hydroxy-2H-pyran-2-one moiety is a key structural feature in a recently discovered new class of non-peptidic HIV protease inhibitors. Therefore, the synthetic methodologies were extended to allow the functionalization of commercially available chemicals. Direct arylation of the pyrone ring at the C-3 and C-5 positions had not been reported until the re-... [Pg.61]

The isomeric 6-hydroxy-2-pyrone (glutaconic anhydride) and its 4-methyl analog (47) react similarly with aryldiazonium salts and on hydrolysis with dilute alkali or acid the hydrazones (48) are transformed into l-aryl-6-oxo-l,6-dihydro-3-pyridazinecarboxylic acids or their 4-methyl analogs (49) in variable yields (28-74%). [Pg.240]

The most common method for the preparation of pyrazoles from other heterocycles is from pyranone-type compounds. Condensation of 2,3-dihydro /7-pyran -ones 787 with various aryl hydrazines in the presence of montmorillonite KSF clay under mild conditions proceeded rapidly to afford enantiomerically pure 5-substituted pyrazoles 788 (Equation 172) <2004TL6033>. Comparable results were obtained when arylhydrazines were reacted with 2-formyl glycals under microwave irradiation <2004TL8587>. Phenylhydrazine and hydrazine were reacted with 3-acetyl-4-hydroxy-6-methyl-2/7-pyran-2-one to afford 4-acetoacetyl-3-methylpyrazolin-5-ones, which were employed in the synthesis of bipyrazoles and pyrazoloisoxazoles <1999JHC1291>. Reaction of 3,3-dialkyl-6-(trifluoromethyl)-2,3-dihy-dro -pyrones with hydrazine hydrate afforded 3-(trifluoromethyl)-5-substituted-pyrazoles <1998RCB1365>. [Pg.104]

The reactions of amidines or guanidines with a-functionalized carbonyl compounds continue to be utilized for the synthesis of imidazoles. Thus, the mixed anhydride of acetic and chloroacetic acids reacts with symmetrical diarylguanidines to give l-aryl-2-arylaminoimidazolin-4-ones, and there is competitive formation of imidazoles and pyrimidines in the reaction of benzamidine with 3-bromobenzo-4-pyrones (18). Imidazoles are minor products, but are favored in nonpolar solvents. The use of a-dicarbonyl compounds with guanidine gives 2-amino-4-hydroxy-4-methyl-4//-imid-azoles, which give excellent yields of 2-aminoimidazoles on catalytic hydrogenation. " ... [Pg.250]

Treatment of MI-220 or MI-221 (R = H, CH3) with aromatic amines in water gives l-aryl-5-hydroxy(or methoxy)-4-pyridone-2-carboxylic acids, which are readily decarboxylated to XII-223, (R = H, CH3) or converted to ethyl esters."" 2-Hydroxymethyl-S-methoxy-4-pyrone, a monomethyl ether of kojic acid, and 2-dialkylaminoethylamines in water give l-(2-dialkylaminoethyl)-2-hydroxymethyl-5-methoxy-4-pyridones (MI-224 R = CH3,C2Hs). Natural maltol glucoside and ammonia or primary amines give the corresponding pyridones (XU-225) when boiled in methanol. ... [Pg.649]


See other pages where 6-Aryl-4-hydroxy-2-pyrones is mentioned: [Pg.45]    [Pg.45]    [Pg.64]    [Pg.283]    [Pg.191]    [Pg.754]    [Pg.179]    [Pg.168]    [Pg.143]    [Pg.45]    [Pg.45]    [Pg.64]    [Pg.812]    [Pg.301]    [Pg.22]    [Pg.767]    [Pg.657]    [Pg.1193]    [Pg.132]    [Pg.283]    [Pg.450]   
See also in sourсe #XX -- [ Pg.45 ]




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3-Aryl-5-hydroxy

4-Hydroxy-2-pyrones

6- Aryl-2-pyrones

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