Reduction of chromano–piperidine-fused isoxazolidines: Tandem intramolecular rearrangements leading to 2-(methylamino)-4-oxo-N-phenyl-N-propyl-4H-chromene-3-carboxamide
Reductive ring opening of isoxazolidine moiety of chromano–piperidine-fused isoxazolidines (3a–c) with HCOONH4 and 10% Pd/C in a mixture of solvents (THF/MeOH) at ambient temperature, affords novel 2-(methylamino)-4-oxo-N-phenyl-N-propyl-4H-chromene-3-carboxamide (4), which is apparently derived from reductive N[sbnd]O bond cleavage followed by tandem intramolecular rearrangements. Plausible mechanistic rationale for the formation of compound 4 is proffered.
Singh, Gagandeep,Gupta, Naman,Gupta, Vivek,Ishar, Mohan Paul Singh
Regio- and stereoselective synthesis of 1-benzopyrano[2,3-b]pyrrolo[2,3-d] pyridines: A microwave-accelerated intramolecular [3+2] cycloaddition reaction of azomethine ylide
Figure represented. Regio- and stereoselective syntheses of tetracyclic compounds having chromone, pyrrolidine, and piperidine rings have been accomplished by an intramolecular [3+2] cycloaddition reaction involving azomethine ylide. The reactions were ca
Substituent-controlled domino-Knoevenagel-hetero Diels - Alder reaction - A one-pot synthesis of polycyclic heterocycles
The reaction of 2-(N-alkenyl-N-aryl)amino-4-oxo-4H-1-benzopyran-3- carbaldehyde with dimedone/Meldrum's acid/4-hydroxycoumarin by heating in ethanol in the presence of pyridine produces polycyclic heterocycles bearing pyridine and pyran rings in a one-pot reaction. The effect of substituents on N-atom of the amino function controls the mode of reaction. Terminal alkenes prefer intramolecular Michael type reaction, but non-terminal alkenes favour Diels-Alder reaction, whereas, under similar condition, 2-(N-alkyl-N-allyl) amino-4-oxo-4H-1-benzopyran-3-carbaldehyde undergoes domino-Knoevenagel-hetero Diels-Alder reaction.
Intramolecular low-temperature 1,3-dipolar cycloadditions of nitrones: synthesis of chromano-heterocycles
In contrast to the reported facile intramolecular 1,3-dipolar cycloadditions of in-situ generated nitrone on heterocyclic systems, reactions of 2-(N-allyl/crotyl/cinnamyl-anilino)-3-formylchromones with N-phenyl-/methylhydroxylamine under comparable condi
Pericyclic transformations at the periphery of chromen-4-one (=4H-1-benzopyran-4-one): An unusual preference for a 1,5-shift of allylic moieties over the ene reaction
Quite unlike the reported facile ene reactions on the periphery of many related heterocyclic systems, similarly disposed moieties on the periphery of the chromen-4-one (=4H-1-benzopyran-4-one) system fail to undergo an ene reaction and display a rather un
Singh, Gurmit,Singh, Gurpinder,Ishar, Mohan Paul S.
p. 169 - 180
(2007/10/03)
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