Described herein is a new visible‐light photocatalytic strategy for the synthesis of enantioenriched dihydrofurans and cyclopentenes by an intramolecular nitro cyclopropane ringexpansionreaction. Mechanistic studies and DFT calculations are used to elucidate the key factors in this new ringexpansionreaction, and the need for the nitro group on the cyclopropane.
development of one-pot organocatalytic dominoMichael/alpha-alkylation reactions between bromomalonates or bromoacetoacetate esters and alpha,beta-unsaturated aldehydes is presented. The chiral-amine-catalyzed reactions with bromomalonates as substrates give access to the corresponding 2-formylcyclopropane derivatives in high yields with excellent diastereoselectivity and up to 99 % ee. The catalytic domino
The title compounds are easily synthesized in good yields by reaction of the Reformatsky reagents derived from α-bromesters, α-bromocarboxamides, and α-bromonitriles with 2-acyl-3-phenyl(or 3-alkyl)-1,1-diethoxycarbonylcyclopropanes.
Biocatalytic Asymmetric Cyclopropanations via Enzyme‐Bound Iminium Ion Intermediates
作者:Andreas Kunzendorf、Guangcai Xu、Mohammad Saifuddin、Thangavelu Saravanan、Gerrit J. Poelarends
DOI:10.1002/anie.202110719
日期:2021.11.2
Engineering of a promiscuous 4-oxalocrotonate tautomerase (4-OT) resulted in an unusual cofactor-independent cyclopropanationenzyme that promotes the stereoselective addition of diethyl 2-chloromalonate to substituted cinnamaldehydes to afford various cyclopropanes with high diastereo- and enantiopurity.
Enantioselective oxidative domino reactions of allylic alcohols to functionalized aldehydes have been developed. The one pot domino oxidation-iminium activation represents a convenient strategy for the enantioselective addition of malonates to allylic alcohols and the asymmetric formation of formyl cyclopropanes.