Synergistic Catalysis between a Dipeptide Phosphonium Salt and a Metal‐Based Lewis Acid for Asymmetric Synthesis of
<i>N</i>
‐Bridged [3.2.1] Ring Systems
作者:Yuan Chen、Jiajia He、Cheng Zhuang、Zanjiao Liu、Kai Xiao、Zhishan Su、Xiaoyu Ren、Tianli Wang
DOI:10.1002/anie.202207334
日期:2022.9.19
method for asymmetric construction of N-bridged [3.2.1] rings by a phosphoniumsalt/silver co-catalyzed cyclization has been developed. This route affords fluorine-installed tropane derivatives in excellent stereoselectivities. The mechanistic results revealed that the silver nitrite was installed on the phosphoniumsalt via hydrogen bonding and simultaneously activated the dipole, in a “sandwich” reaction
Catalytic α-Allylation of Unprotected Amino Acid Esters
作者:Ping Fang、Mani Raj Chaulagain、Zachary D. Aron
DOI:10.1021/ol300665n
日期:2012.4.20
Catalytic alpha-allylation of unprotected amino acid esters to produce alpha-quaternary alpha-allyl amino acid esters is reported. Catalytic loadings of picolinaldehyde and Ni(II) salts induce preferential reactivity at the enolizable alpha-carbon of amino acid esters over the free nitrogen with electrophilic palladium pi-allyl complexes. Fourteen examples are given. Additionally, the use of chiral ligands to access enantioenriched alpha-quaternary amino acid esters from racemic precursors is demonstrated by the enantioselective synthesis of alpha-allyl phenylalanine methyl ester from racemic phenylalanine methyl ester.