cyanohydrins through the concomitant construction of three chiral carbon centers is reported. This protocol facilitates the concise synthesis of opticallyactive tetrahydropyran derivatives, which are ubiquitous scaffolds found in various bioactive compounds, through the simultaneous construction of multiple bonds and stereogeniccenters, including tetrasubstituted chiral carbons. The resulting products
Enantioselective Addition of Alkynyl Ketones to Nitroolefins Assisted by Brønsted Base/H‐Bonding Catalysis
作者:Teresa E. Campano、Igor Iriarte、Olatz Olaizola、Julen Etxabe、Antonia Mielgo、Iñaki Ganboa、José M. Odriozola、Jesús M. García、Mikel Oiarbide、Claudio Palomo
DOI:10.1002/chem.201805542
日期:2019.3.21
sets of enolizable alkynyl ketones (including methyl ynones with α‐aryl, α‐alkenyl, and α‐alkoxy groups) were able to react smoothly with nitroolefins with the assistance of bifunctional Brønsted base/H‐bond catalysts to provide adducts with two consecutive tertiary stereocenters in a highly diastereo‐ and enantioselective fashion. Further transformation of the obtained adducts into optically active acyclic
of hybrid catalysts incorporating chloramphenicol base with another chiral scaffold using a squaramide linker have been developed and successfully applied in Michael addition of 2,3-dihydrobenzofuran-2-carboxylates to nitroolefins. The controlling experiments suggested that the hybrid catalysts were more reactive than non-hybridized bifunctional catalysts and the matching of chiralities between two
The first regio-, diastereo-, and enantioselective direct Michaelreaction of β,γ-unsaturated ketones with nitroolefins is enabled by Brønsted base/hydrogen-bonding bifunctional catalysis. A squaramide-substituted tertiary amine catalyzes the reaction of a broad range of β,γ-unsaturated ketones to proceed at the α-site exclusively, giving rise to adducts with two consecutive tertiary carbon stereocenters
Organocatalytic Enantio- and Diastereoselective Construction of <i>syn</i>-1,3-Diol Motifs via Dynamic Kinetic Resolution of In Situ Generated Chiral Cyanohydrins
syn-1,3-dioxanes as protected 1,3-diols via dynamickineticresolution of in situ generated chiral cyanohydrins has been developed. This method involves a reversible cyanohydrin formation/hemiacetalization/intramolecular oxy-Michael addition reactioncascade, affording a chiral syn-1,3-diol structure with simultaneous construction of two stereogenic centers. The use of trifluoromethyl ketones is crucial