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 conditions, afford fused isoxazolidines only in low to moderate yields; the corresponding amides derived from rearrangement of in situgenerated nitrones are formed as
Reduction of chromano–piperidine-fused isoxazolidines: Tandem intramolecular rearrangements leading to 2-(methylamino)-4-oxo- N -phenyl- N -propyl-4 H -chromene-3-carboxamide
作者:Gagandeep Singh、Naman Gupta、Vivek Gupta、Mohan Paul Singh Ishar
DOI:10.1016/j.tetlet.2017.05.032
日期:2017.6
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 NO bond cleavage followed by tandem intramolecular rearrangements. Plausible mechanistic
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 polycyclicheterocycles 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
通过在吡啶存在下于乙醇中加热,使2-(N-烯基-N-芳基)氨基-4-氧代-4 H -1-苯并吡喃-3-甲醛与二甲酮/麦德鲁姆酸/ 4-羟基香豆素反应生成多环一锅反应中带有吡啶和吡喃环的杂环。取代基对氨基官能团的N-原子的影响控制了反应方式。末端烯烃偏爱分子内迈克尔型反应,但非末端烯烃偏爱Diels-Alder反应,而在类似条件下,2-(N-烷基-N-烯丙基)氨基-4-氧代-4 H -1-苯并吡喃-3 -甲醛经历多米诺-Knoevenagel-杂Diels-Alder反应。