3-Ethoxycyclobutanones reacted with pyridines, quinolines, and isoquinolines to give the corresponding formal [4+2] cycloadducts, 9a-hydro-2H-quinolizin-2-one derivatives, by using Me3SiOTf in acetonitrile. Cycloaddition of 3-ethoxy-2-monoalkylcyclobutanones to 5-nitroquinoline or 4-cyanopyridine proceeded stereoselectively.
Lewis-acid Promoted Chemoselective Condensation of 2-Aminobenzimidazoles or 3-Aminoindazoles with 3-Ethoxycyclobutanones to Construct Fused Nitrogen heterocycles
作者:Weiguang Kong、Yao Zhou、Qiuling Song
DOI:10.1002/adsc.201701641
日期:2018.5.16
or 3‐aminoindazoles with 3‐ethoxycyclobutanones is presented. Diverse fused heterocyclesbenzo[4,5]‐imidazo[1,2‐a]pyrimidine and pyrimido[1,2‐b]‐indazole derivatives were obtained in moderate to high yields under mild conditions, the reaction mechanism of which was in sharp contrast to previous [3+3] annulation reaction of 3‐ethoxycyclobutanones.
Lewis Acid-Mediated [3+3] Annulation for the Construction of Substituted Pyrimidine and Pyridine Derivatives
作者:Yao Zhou、Zhonghe Tang、Qiuling Song
DOI:10.1002/adsc.201601386
日期:2017.3.20
A direct and single‐step procedure towards substituted pyrimidine and pyridine derivatives via Lewis acid‐promoted [3+3] annulation between 3‐ethoxycyclobutanones and enamines or amidines is presented. Diverse substituted pyrimidine and pyridine derivatives were obtained in good to high yields with a wide substrate scope.
Formal [4+2] cycloaddition of 3-ethoxycyclobutanones with azo compounds
作者:Yusuke Shima、Jun-ichi Matsuo
DOI:10.1016/j.tetlet.2016.07.087
日期:2016.9
with EtAlCl2, and intermolecular formal [4+2] cycloaddition of the zwitterionic intermediate proceeded with azobenzenes to give 2,3-dihydro-pyridazin-4(1H)-ones after elimination of ethanol. Regioselectivity for cycloaddition of unsymmetrical azobenzenes, ring contraction and chemoselective reduction of 2,3-dihydro-pyridazin-4(1H)-ones, and [4+2] cycloaddition to 4-phenyl-1,2,4-triazolin-3,5-dione are
way: A formal [4+2] cycloaddition between various cyclobutanones and indoles proceeded efficiently under Lewis acid catalysis (see scheme; PG = protecting group). The regioselectivity of the reaction could be controlled in such a way that each of the two possible regioisomers of a cycloaddition product could be synthesized selectively. The usefulness of this reaction for the total synthesis of hydrocarbazole