1,3-dipolarcycloaddition is a powerful route for the synthesis of five-membered heterocycles. The [3+2] cycloadditions of some alpha-methylene-gamma-buryrolactones, namely 3-methylenedihydro-(3H)-furan-2-one (1) and itaconic anhydride (2) were Studied. Their reactions with arylnitrile oxides (3) and Caroyl-N-phenylnitrones (7) proceed with complete regioselectivity. From a stereochemical point of
A series of mono- and di-substituted pentafulvenes 1–3 was reacted with aroylnitrones 4 to afford the corresponding fused bicyclic monoadducts 5–9, generally as a mixture of isomers. The stereochemistry of the addition reaction was established by 1D and 2D NMR spectroscopies or X-ray crystallography. Performance of theoretical calculations has been undertaken in order to rationalize the important differences in regioselectivity displayed by the reaction.
一系列单取代和双取代的五富烯 1-3 与芳酰硝酮 4 反应,得到相应的稠合双环单加合物 5-9,通常为异构体混合物。加成反应的立体化学通过一维和二维核磁共振波谱或 X 射线晶体学建立。为了合理化反应所表现出的区域选择性的重要差异,已经进行了理论计算。
Endo-Selective Asymmetric Inverse Electron-Demand 1,3-Dipolar Cycloaddition Reaction of Nitrones
Cycloaddition of nitrones 1 with methylene-gamma-butyrolactones 2, 3 and 4 afforded spiroadducts 5, 6 and 7 with high selectivity. Mixtures of diastereoisomers were usually obtained, whose structures were established by 1H and 13C NMR spectroscopies or X-ray crystallography. Treatment of spiroadducts in acidic and alkaline media led to different, unexpected and novel rearrangements.