used as phase transfer catalysts in asymmetric Michaeladdition reactions under mild conditions to afford the adducts in a few cases in good to excellent enantioselectivities. The addition of 2‐nitropropane to trans‐chalcone, and the reaction of diethyl acetamidomalonate with β‐nitrostyrene resulted in the chiral Michael adducts in good enantioselectivities (90% and 95%, respectively). The substituents
the addition to chalcone, in up to 78% ee in the reaction with benzylidene malononitrile, and in up to 76% ee in the reaction with 2-benzylidene-1,3-diphenyl-1,3-propanedione applying α-D-galactoside-based crown ethers as the catalysts. In the Michael addition, the substituents of the chalcone had a considerable impact on the outcome of the reactions. Quantum chemical calculations have also been employed
Abstract Cyclopropane were obtained from electron deficient olefins and acid carbon compounds by oxidation by iodine in the presence of KF on alumina. The reaction allows the synthesis of cyclopropanediyldiphosphonates.
[3+3] Annulation of donor–acceptor cyclopropanes with mercaptoacetaldehyde: application to the synthesis of tetrasubstituted thiophenes
作者:Gopal Sathishkannan、Kannupal Srinivasan
DOI:10.1039/c4cc00565a
日期:——
A conceptually new method for synthesis of tetrasubstituted thiophenes in two steps from trans-2-aroyl-3-aryl-cyclopropane-1,1-dicarboxylates and 1,4-dithiane-2,5-diol has been developed. It involves AlCl3-mediated [3+3] annulation of the cyclopropane-derived 1,3-zwitterionic intermediates with in situ generated mercaptoacetaldehyde, followed by DBU-induced rearrangement of the resulting tetrahydrothiopyranols. The target thiophenes are produced in 55â82% yields.
AlCl<sub>3</sub>-Promoted Highly Regio- and Diastereoselective [3 + 2] Cycloadditions of Activated Cyclopropanes and Aromatic Aldehydes: Construction of 2,5-Diaryl-3,3,4-trisubstituted Tetrahydrofurans
The AlCl3-catalyzed [3 + 2] cycloaddition reaction of diethyl trans-2,3-disubstituted cyclopropane-1,1-dicarboxylates and aromatic aldehydes was carried out under mild conditions to provide a series of diethyl 2,5-diaryl-4-benzoyltetrahydrofuran-3,3-dicarboxylates in moderate to good yields with excellent diastereoselectivities. While common 2,5-cis products were obtained with electron-neutral or electron-poor