- Forming All-Carbon Quaternary Stereocenters by Organocatalytic Aminomethylation: Concise Access to β2,2-Amino Acids
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The asymmetric synthesis of β2,2-amino acids remains a formidable challenge in organic synthesis. Here a novel organocatalytic enantioselective aminomethylation of ketenes with stable and readily available N,O-acetals is reported, providing β2,2-amino esters bearing an all-carbon quaternary stereogenic center in high enantiomeric ratios with a catalytic amount of chiral phosphoric acid. Typically, this transformation probably proceeds through an asymmetric counter-anion-directed catalysis. As a result, a concise, practical, and atom-economic protocol toward rapidly access to β2,2-amino acids has been developed.
- Shao, Ying,Sun, Jiangtao,Tang, Shengbiao,Wang, Kai,Yu, Jianliang
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supporting information
p. 23516 - 23520
(2020/10/21)
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- Addition-Rearrangement of Ketenes with Lithium N- tert-Butanesulfinamides: Enantioselective Synthesis of α,α-Disubstituted α-Hydroxycarboxylic Acid Derivatives
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Addition of the lithium salts of chiral N-substituted tert-butanesulfinamides to ketenes and subsequent silylation initiates stereoselective [2,3]-rearrangement, which affords enantioenriched α,α-disubstituted α-sulfenyloxy carboxamides through a reaction
- Ma, Peng-Ju,Tang, Fan,Yao, Yun,Lu, Chong-Dao
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supporting information
p. 4671 - 4675
(2019/06/17)
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- Stereo- and Chemodivergent NHC-Promoted Functionalisation of Arylalkylketenes with Chloral
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Stereo- and chemodivergent enantioselective reaction pathways are observed upon treatment of alkylarylketenes and trichloroacetaldehyde (chloral) with N-heterocyclic carbenes, giving selectively either β-lactones (up to 88:12 dr, up to 94% ee) or α-chloroesters (up to 94% ee). Either 2-arylsubstitution or an α-branched iPr alkyl substituent within the ketene favours the chlorination pathway, allowing chloral to be used as an electrophilic chlorinating reagent in asymmetric catalysis.
- Douglas, James J.,Churchill, Gwydion,Slawin, Alexandra M. Z.,Fox, David J.,Smith, Andrew D.
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supporting information
p. 16354 - 16358
(2015/11/09)
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