Diels-Alder Reactions for the Construction of Cyclopropylarenes
作者:Marion Arndt、Gerhard Hilt、Alexander F. Khlebnikov、Sergei I. Kozhushkov、Armin de Meijere
DOI:10.1002/ejoc.201200105
日期:2012.6
cobalt-catalyzed Diels–Alder reactions are described. The cycloaddition processes generated the desired bicyclopropyl-substituted arene derivatives in moderate to good yields, depending on the steric congestion of the reaction partners. The regioselectivity of the cycloaddition was controlled by the ligand coordinated to the cobalt center. The cyclopropyl moiety remained unchanged over the course of the Diels–Alder
Convenient Synthesis of Ethenylcyclopropane and Some 2-Cyclopropylcyclopropane Derivatives¹
作者:Armin de Meijere、Valentin Rassadin、Viktor Sokolov、Alexander Khlebnikov、Nikolay Ulin、Sergei Kozhushkov
DOI:10.1055/s-0031-1289600
日期:2012.2
diazoacetate gave ethyl 2-cyclopropylcyclopropanecarboxylate (cis/trans-9, ratio 1:1.4) in 80% yield. The latter was also prepared in 79% overall yield by sequential cyclopropanation of buta-1,3-diene with ethyl diazoacetate [under Rh2(OAc)4 catalysis] and diiodomethane/diethylzinc/trifluoroacetic acid. Curtius degradation of 2-cyclopropylcyclopropanecarboxylic acid (obtained by hydrolysis of the ester) gave