Formal [4 + 2] Cycloadditions of Anhydrides and α,β-Unsaturated <i>N</i>-Tosyl Ketimines
作者:Noah P. Burlow、Sara Y. Howard、Carla M. Saunders、James C. Fettinger、Dean J. Tantillo、Jared T. Shaw
DOI:10.1021/acs.orglett.8b04091
日期:2019.2.15
ketone-derived imines is reported. Cyclic, enolizable anhydrides undergo a base-promoted conjugate addition reaction with α,β-unsaturated N-tosyl ketimines, followed by an intramolecular acylation to give formal [4 + 2] cycloaddition products. The carboxylic acid-containing products are formed with modest selectivity for the cis-diastereomer and can be fully epimerized to the trans-diastereomer upon esterification
Asymmetric Conjugate Addition of Malonate Esters to α,β-Unsaturated<i>N</i>-Sulfonyl Imines: An Expeditious Route to Chiral δ-Aminoesters and Piperidones
作者:Miguel Espinosa、Gonzalo Blay、Luz Cardona、José R. Pedro
DOI:10.1002/chem.201302687
日期:2013.10.25
The asymmetric conjugate addition of malonate esters to α,β‐unsaturated N‐sulfonyl imines is catalyzed by PyBOX/La(OTf)3 complexes in the presence of 4 Å MS. The reaction gives the corresponding E enamines bearing a stereogenic center at the allylic position with good yields and enantiomeric ratios up to 97:3. This reaction provides a synthetic entry to chiral δ‐aminoesters and piperidones.
Enantioselective Stetter Reactions Catalyzed by Bis(amino)cyclopropenylidenes: Important Role for Water as an Additive
作者:Mehran Rezazadeh Khalkhali、Myron M. D. Wilde、Michel Gravel
DOI:10.1021/acs.orglett.0c03879
日期:2021.1.1
The first highly enantioselective intermolecular Stetter reaction using simple enones is reported. A series of novel chiral BAC structures were designed and prepared. They were tested in the Stetter reaction with simple aldehydes and enones. The products were generated in excellent yields and enantioselectivities (up to 94% ee). Surprisingly, a substoichiometric amount of water was crucial to obtain
Restoration of catalytic activity by the preservation of ligand structure: Cu-catalysed asymmetric conjugate addition with 1,1-diborylmethane
作者:Changhee Kim、Byeongdo Roh、Hong Geun Lee
DOI:10.1039/d0sc06543a
日期:——
conditions that control the amount of nucleophilic alkoxide base, which is the origin of ligand decomposition. Overall, the strategy has been successfully applied to a new class of asymmetric conjugate addition reactions with bis[(pinacolato)boryl]methane, in which α,β-unsaturated enones are utilised as substrates.
An efficient and convenient highly enantioselective Michaeladdition of malononitrile to enones has been developed by using quinine as the organocatalyst. The adducts were isolated in excellent yield and high asymmetric induction (up to 95% ee). An easy route to difficultly accessible ester derivatives has been also disclosed.