Cationic Chiral Fluorinated Oxazaborolidines. More Potent, Second-Generation Catalysts for Highly Enantioselective Cycloaddition Reactions
作者:Karla Mahender Reddy、Eswar Bhimireddy、Barla Thirupathi、Simon Breitler、Shunming Yu、E. J. Corey
DOI:10.1021/jacs.6b00100
日期:2016.2.24
placement of fluorine substituents in the chiral ligand. This approach has led to a new, second-generation family of chiral oxazaborolidinium cationic species which can be used to effect many Diels-Alder reactions in >95% yield and >95% ee usingcatalyst loadings at the 1-2 mol % level. The easy recovery of the chiral ligand makes the application of these new catalysts especially attractive for large-scale
Allyl‐Palladium‐Catalyzed Ketone Dehydrogenation Enables Telescoping with Enone α,β‐Vicinal Difunctionalization
作者:Yifeng Chen、David Huang、Yizhou Zhao、Timothy R. Newhouse
DOI:10.1002/anie.201704874
日期:2017.7.3
The telescoping of allyl‐palladium catalyzed ketone dehydrogenation with organocuprate conjugate addition chemistry allows for the introduction of aryl, heteroaryl, vinyl, acyl, methyl, and other functionalized alkyl groups chemoselectively to a wide variety of unactivated ketone compounds via their enone counterparts. The compatibility of the dehydrogenation conditions additionally allows for efficient
Chiral Oxazaborolidine−Aluminum Bromide Complexes Are Unusually Powerful and Effective Catalysts for Enantioselective Diels−Alder Reactions
作者:Duan Liu、Eda Canales、E. J. Corey
DOI:10.1021/ja068637r
日期:2007.2.1
acid catalyst than protonated 1 (i.e., 2) for enantioselectiveDiels−Alderreactions. Only 4 mol % of catalyst 3 is required to achieve yields and enantiomeric purities of 90% over a broad range of achiraldienes and dienophiles. The ligand from which 3 is derived can be recovered easily and with high efficiency. The method is illustrated by 22 examples.
Synthesis of Cyclic Enones by Allyl-Palladium-Catalyzed α,β-Dehydrogenation
作者:David Huang、Yizhou Zhao、Timothy R. Newhouse
DOI:10.1021/acs.orglett.7b03818
日期:2018.2.2
The use of allyl-palladium catalysis for the one-step α,β-dehydrogenation of ketones via their zinc enolates is reported. The optimized protocol utilizes commercially available Zn(TMP)2 as base and diethyl allyl phosphate as oxidant. Notably, this transformation operates under salt-free conditions and tolerates a diverse scope of cycloalkanones.
of an amine was used to not only simplify the preparation of the catalysts but also increase Lewis acidity of the boron atom. The in situ generated borenium salts showed exceptional Lewis acidity and successfully catalyzed asymmetric Diels–Alderreactions of cyclopentadiene and dienophiles in excellent yields and enantioselectivities. The NMR studies of these oxathiaborolium structures were reported