Hypoiodite-catalysed oxidative cyclisation of Michael adducts of chalcones with 1,3-dicarbonyl compounds: a facile and versatile approach to substituted furans and cyclopropanes
Through hypoiodite catalysis, the oxidative cyclisation of Michael adducts of chalcones with 1,3-dicarbonyl compounds for divergent synthesis of either furans or cyclopropanes is developed. The selective synthesis of major products...
The title compounds are easily synthesized in good yields by reaction of the Reformatsky reagents derived from α-bromesters, α-bromocarboxamides, and α-bromonitriles with 2-acyl-3-phenyl(or 3-alkyl)-1,1-diethoxycarbonylcyclopropanes.
The [3 + 2] annulations of γ-butyrolactone fused donor–acceptor (D–A) cyclopropanes with aromatic isothiocyanates and dialkyl carbodiimides promoted by FeCl3 is reported. A series of bicyclic/polycyclic γ-butyrolactone fused thioimidates and γ-butyrolactone fused amidines containing four contiguous stereogenic centers were obtained in excellent yields as single stereoisomers.
Vicarious nucleophilic substitution of hydrogen in electrophilic alkenes
作者:Mieczysłlaw Ma̧kosza、Andrzej Kwast
DOI:10.1016/s0040-4020(01)80963-7
日期:1991.1
Carbanions containing leaving groups react in the presence of base with electrophilicalkenes giving products in which vinylic hydrogen is replaced with the carbanion moiety. They are formed via addition - β-elimination pathway analogous to the vicarious nucleophilicsubstitution in nitroarenes. In some cases, however, the cyclization - ring opening process takes place instead.
1-Carboxy (or 1-ethoxycarbonyl)-3 oxabicyclo[3.1.0]hexane-2-ones (2 and 4) are readily prepared from 2-acyl-3-methyl (or 3-phenyl)-1,1-dicarboxycylcopropanes (1) and 2-acyl-3-alkyl (or 3-phenyl)-1.1-diethoxycarbonylcyclopropanes (3), respectively, in 70-99%, overall yields.