<i>C</i><sub>2</sub>-Symmetric Cu(II) Complexes as Chiral Lewis Acids. Catalytic, Enantioselective Cycloadditions of Silyl Ketenes
作者:David A. Evans、Jacob M. Janey
DOI:10.1021/ol016096z
日期:2001.6.1
[reaction: see text] C(2)-Symmetric bis(oxazoline)-Cu(II) complexes (4a-g) catalyze the enantioselective [2 + 2] cycloaddition between (silyl)ketenes and chelating carbonyl substrates. A range of substituted beta-lactones can be produced in excellent yields and selectivities. It was also found that (trimethylsilyl)ketene (1) may also undergo a highly selective hetero Diels-Alder reaction with beta
stereoselective synthesis of polyring-fused heterocyclic compounds based on diene-transmissive hetero-Diels–Alder reactions utilizing β,γ-unsaturated α-keto esters. This protocol involves the initial endo- or exo-selective Diels–Alder (DA) reactions with electron-rich dienophiles, methylenation of the ester carbonyl groups with the Tebbe reagent, and a stereoselective second DA reaction with electron-deficient
Cu(II) complexes of hydroxy oxazolines derived from (+)-(S)-ketopinic acidcatalyze the asymmetric hetero-Diels-Alder cycloaddition of enol ethers and β,γ-unsaturated α-keto esters. The reaction takes place with unprecedented exo selectivity providing 2,4-trans-disubstituted chiral 2,3-dihydropyrans with up to 88% ee.
Chiral <i>C</i><sub>2</sub>-Symmetric Cu(II) Complex Immobilized in Ionic Liquids: A Recoverable Catalytic System for Enantioselective Hetero-Diels-Alder Reaction
作者:B. Kim、Yong Shin、Chang-Eun Yeom、Mi Kim
DOI:10.1055/s-2007-1000830
日期:2008.1
Hydrophobic ionicliquids such as [Bmim]PF 6 and [Bmim]SbF 6 were used successfully as powerful media for bis(oxazoline)-copper-catalyzed asymmetric hetero-Diels-Alder reactions. The reactivities and stereoselectivities were comparable ( ENDO/ EXO up to 97:3 and up to 94% ee, respectively) to those of the corresponding homogeneous reactions. Furthermore, the reaction was remarkably accelerated in [Bmim]PF
Enantioselective Synthesis of Dihydropyrans. Catalysis of Hetero Diels−Alder Reactions by Bis(oxazoline) Copper(II) Complexes
作者:David A. Evans、Jeffrey S. Johnson、Edward J. Olhava
DOI:10.1021/ja992175i
日期:2000.3.1
C2-symmetric bis(oxazoline)−Cu(II) complexes 1 and 2 catalyze the inverse electron demand hetero Diels−Alder reaction of α,β-unsaturated carbonyl compounds (heterodiene) with electron-rich olefins (heterodienophile) in high diastereo- and enantioselectivity. α,β-Unsaturated acyl phosphonates and β,γ-unsaturated α-keto esters and amides are effective heterodienes, while enol ethers and sulfides function