Shuquan Wu

Bio: Shuquan Wu is an academic researcher from Guizhou University. The author has contributed to research in topics: Carbene & Catalysis. The author has an hindex of 5, co-authored 6 publications receiving 68 citations.

NHC-Catalyzed Chemoselective Reactions of Enals and Aminobenzaldehydes for Access to Chiral Dihydroquinolines.

Abstract: An N-heterocyclic carbene (NHC)-catalyzed reaction between α-bromoenals and 2-aminoaldehydes has been developed. Key steps include chemoselective reaction of the NHC catalyst with one of the aldehyde substrates (the bromoenal) to eventually generate an α,β-unsaturated acylazolium intermediate. Addition of the nitrogen atom of aminoaldehyde to the unsaturated azolium ester intermediate followed by intramolecular aldol reaction, β-lactone formation, and decarboxylation leads to chiral dihydroquinolines with high optical purity. The dihydroquinoline products, which are quickly prepared by using this method, can be readily transformed into a diverse set of functional molecules such as pyridines and chiral piperidines.

Carbene-Catalyzed Enantioselective Sulfonylation of Enone Aryl Aldehydes: A New Mode of Breslow Intermediate Oxidation.

Abstract: A carbene-catalyzed sulfonylation reaction between enone aryl aldehydes and sulfonyl chlorides is disclosed. The reaction effectively installs sulfone moieties in a highly enantioselective manner to afford sulfone-containing bicyclic lactones. The sulfonyl chloride behaves both as an oxidant and a nucleophilic substrate (via its reduced form) in this N-heterocyclic carbene (NHC)-catalyzed process. The NHC catalyst provides both activation and stereoselectivity control on a very remote site of enone aryl aldehyde substrates. Water plays an important role in modulating catalyst deactivation and reactivation routes that involve reactions between NHC and sulfonyl chloride. Experimental studies and DFT calculations suggest that an unprecedented intermediate and a new oxidation mode of the NHC-derived Breslow intermediate are involved in the new asymmetric sulfonylation reaction.

N-Heterocyclic Carbene Catalyzed Photoenolization/Diels-Alder Reaction of Acid Fluorides.

Abstract: The combination of light activation and N-heterocyclic carbene (NHC) organocatalysis has enabled the use of acid fluorides as substrates in a UVA-light-mediated photochemical transformation previously observed only with aromatic aldehydes and ketones. Stoichiometric studies and TD-DFT calculations support a mechanism involving the photoactivation of an ortho-toluoyl azolium intermediate, which exhibits "ketone-like" photochemical reactivity under UVA irradiation. Using this photo-NHC catalysis approach, a novel photoenolization/Diels-Alder (PEDA) process was developed that leads to diverse isochroman-1-one derivatives.

N-Heterocyclic Carbene-Catalyzed Atroposelective Annulation for Access to Thiazine Derivatives with C-N Axial Chirality.

Abstract: A catalytic atroposelective cycloaddition reaction between thioureas and ynals is developed. This reaction features the first NHC-catalyzed addition of thioureas to acetylenic acylazolium intermediates to eventually set up C-N axial chirality with excellent optical purities. The obtained axially chiral thiazine derivative products bear multiple functional groups and are feasible for further transformations.

Advances in organocatalytic asymmetric reactions of vinylindoles: powerful access to enantioenriched indole derivatives

Abstract: Enantioenriched indole derivatives are widely found in natural products, pharmaceuticals and bioactive compounds. Therefore, developing efficient methods for the synthesis of enantioenriched indole derivatives has become an important goal in the community of organic chemistry. To this end, chemists have designed and developed a variety of indole-containing platform molecules and their related catalytic asymmetric reactions. Among these approaches, vinylindoles have proved to be versatile platform molecules for accessing enantioenriched indole derivatives via catalytic asymmetric reactions, especially organocatalytic asymmetric reactions. Based on this approach, a plethora of chiral indole derivatives have been synthesized with optical purity and structural complexity. This review summarizes advances in vinylindole-based organocatalytic asymmetric reactions since 2008 and includes the applications of some methodologies in the total synthesis of natural products. In addition, this review points out the remaining challenges in this research area to be confronted by organic chemists, which will shed light on the future development of this area.

Revealing the Similarities of α,β‐Unsaturated Iminiums and Acylazoliums in Organocatalysis

Abstract: The secondary amine-catalyzed reactions proceeding via I±,I²-unsaturated iminiums and the N-heterocyclic carbene (NHC)-catalyzed transformations taking place via I±,I²-unsaturated acylazoliums are the two widely used electrophilic intermediates in organocatalysis. Over the last two decades, these two intermediates are extensively utilized for the enantioselective construction of valuable molecules. Both intermediates are generated by the covalent binding of catalysts to the substrates leading to LUMO activation of I±,I²-unsaturated carbonyls. A variety of soft nucleophiles are known to add to the I±,I²-unsaturated iminiums and acylazoliums in a conjugate fashion, and in many cases, striking similarity in reactivity has been observed. Having said this, there are few cases where these intermediates exhibit difference in reactivity. This Minireview is aimed at highlighting the resemblances in reactivity between I±,I²-unsaturated iminiums and acylazoliums thereby shedding light on the unnoticed parallels of the two intermediates in organocatalysis. © 2020 Wiley-VCH GmbH