One-pot organocatalytic domino Michael/alpha-alkylation reactions: direct catalytic enantioselective cyclopropanation and cyclopentanation reactions.
The development of one-pot organocatalytic domino Michael/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 Michael/alpha-alkylation reactions between 4-bromo-acetoacetate and enals provide a route for the synthesis of functionalized cyclopentanones in good to high yields with 93-99 % ee. The products from the organocatalytic reactions were also reduced with high diastereoselectivity to the corresponding cyclopropanols and cyclopentanols, respectively. Moreover, one-pot combinations of amine and heterocyclic carbene catalysis (AHCC) enabled the highly enantioselective synthesis of beta-malonate esters (91-97 % ee) from the reaction between bromomalonates and enals. The tandem catalysis included the catalytic domino reaction followed by catalytic in situ chemoselective ring-opening of the 2-formylcyclopropane intermediates.
Ibrahem
Ismail
I
Department of Organic Chemistry, The Arrhenius Laboratory, Stockholm University, Stockholm, Sweden.
Zhao
Gui-Ling
GL
Rios
Ramon
R
Vesely
Jan
J
Sundén
Henrik
H
Dziedzic
Pawel
P
Córdova
Armando
A