Chromone-3-carbaldehydes

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... 

Hydroxyacetophenone reacts with DMF under Vilsmeier conditions to yield chromone-3-carbaldehyde (72LA(765)8). The reaction appears to be generally applicable, various substituents being acceptable in the aromatic ring (74T3553). Furthermore, acetylhydroxy-naphthalenes yield the corresponding benzochromones, and the pyranochromone (452) is formed from the appropriately substituted coumarin. 

An efficient and diastereoselective method for preparing ( )-3-styrylchromones 445 has been reported by the reaction of chromone-3-carbaldehyde 448 with phenylacetic acids 444 in the presence of potassium /< rt-butoxide under heating or microwave conditions (Scheme 77) <2004SL2717>. Diels-Alder reactions of 2-styrylchromones 446 with ort o-benzoquinodimethane afforded cycloadducts that can be converted into benzoflavone derivatives such as 447 (Scheme 78) <1999EJO 35>. 

Chromone-3-carbaldehydes undergo Diels-Alder reactions with ort o-benzoquinodimethane 819 and deformyla-tion to yield initially benzo[b]-1,6,6a, 12a-tetrahydroxanthones 820, which are easily transformed into their corresponding benzo[ ]xanthones upon treatment with I2-DMSO (Scheme 232) <2002T105>. 

Chromone-3-carbaldehydes 130 can undergo a MBH reaction with activated alkenes, such as acrylonitrile, methyl acrylate and methyl vinyl ketone,by... 

In addition, 12 was reported to be a suitable organocatalyst for other reactions, including amination of a-cyanoacetates or P-carbonyl esters by reaction with azodi-carboxylate followed by nitrogen-nitrogen bond cleavage of the resultant hydrazine [51]. Recently, a P-isocupreidine with a biphenyl group at C6 instead of a hydroxyl functionality was reported to catalyze the enantioselective [4-1-2] annulation of substituted chromone-3-carbaldehydes and related imines (Scheme 6.22) [52]. 

Chromone carbaldehyde 407 reacts with o-benzoquinodimethane 408 in a Diels-Alder reaction and concomitant deformylation to give a diastereomeric mixture of tetrahydrobenzo[ ]xanthones 409. Subsequent oxidation provides benzo[ ]xanthones 410 in good yields (Scheme 67) <2002T997>. 

Benzoxepin-4-carbaldehyde, dihydro-from chromones, 3, 713 Benzoxepin-4(3H)-one from isochromanone, 3, 726 [l]Benzoxepino[3,4-d]selenazoles synthesis, 6, 345 Benzoxepins... 

Methylchromones and chromone-2-carbaldehyde are converted to 3-chlorochromones in good yield upon reaction with sodium hypochlorite (Scheme 49). The selective substitution of chlorine at C-3 is considered to involve the addition of NaO Cl1 to the C(2)-C(3) double bond followed by elimination of NaOH <1998SC3827>. 

Treatment of a hydroxy carbaldehyde precursor with chloroacetone in refluxing THF in the presence of potassium carbonate and 18-crown-6 resulted in the formation of the 2-acetyl furo-chromone (52) in 53% yield (Equation (25)) <84TL2953>. 

The Pd-catalysed Miyaura-Suzuki coupling of aryltrifluoroborates with 4-tosyloxycoumarins in aqueous conditions offers an attractive route to 4-arylcoumarins <06TL1525> and 4-hydroxycoumarins have been converted into a mixture of predominantly thiopyrano[5, 4 3,4]- pyrano[5,6-c]coumarins and [6,5-c]chromones in a one-pot tandem Knoevenagel - HDA sequence with an S-prenylated 1-phenyl-lff-pyrazole-4-carbaldehyde <06TL2265>. The benzopyrano[4,3-c]benzopyranone system can be obtained from 3-aryl-4-methylcoumarins by deprotonation of the methyl function and subsequent elaboration <06TL5909>. 

Oxobenzopyran-3-carbaldehyde (3-formylchromone) continues to prove a valuable synthetic intermediate. A one-pot synthesis of 4-oxobenzopyran-3-nitriles is based on a Vilsmeier-Haaek synthesis of 4-oxobenzopyran-3-carbaldehyde <04TL847>. 3-Formyl-chromones react with cyanacetamides and other electron-deficient acetic acid amides to give... 

Li, Y., Yang, Z-Y., Wu, J-C. (2010). Synthesis, crystal structures, biological activities and fluorescence studies oftransition metal complexes with 3-carbaldehyde chromone thiosemicarbazone. Europ.. Med. Chem., 45, pp. 5692-5701, ISSN 0223-5234... 

TMSOTf provided indolizines 504 in 38 55% yield (Seheme 4.151). Subsequently, they also demonstrated a facile synthesis of indolizine-fused chromones 505 from the reaction between the MBH adducts of pyridine-2-carbaldehyde and l-benzopyran-4(4ii/)-ones (Scheme 4.152) ... 

Shelke et al. [80] S5mthesized various fluorine-containing compounds by conventional and nonconventional procedures by ultrasonication and microwave techniques. Various 3-substituted-l-phenyl-lH-pyrazole-4-carbaldehydes were treated with 3-(trifluoromethyl)-l-phenyl-lH-pyrazol-5(4H)-one (83) to give 4-((3-(4-aryl)-l-phenyl-lH-pyrazol-4-yl) methylene)-3-(trifluoromethyl)-l-phenyl-lH-pyrazol-5(4H)-one (85). Equivalent mole of 3-formylchromone and 3-(trifluoromethyl)-l-phenyl-lH-pyrazol-5(4H)-one by conventional method and nonconventional methods gave 3-(trifluoromethyl)-4-(4-oxo-4H chromon-3-yl)-methylene-l-phenyl-lH-pyrazol-(4H)-one (84) (Scheme 21). Compounds 84 and 85 were obtained in slightly better yields within 5-10 min under ultrasonication than in 2-3 min with microwave irradiation. 

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