Rhodium-Catalyzed Double Hydroboration of Quinolines

Title

Rhodium-Catalyzed Double Hydroboration of Quinolines

Speaker

Mr. Ruibin Wang (PhD Student in Chemistry under the supervision Prof. Sehoon Park/GTIIT, Prof. Moris S. Eisen/Technion)

Host

Mr. Xuhui Zheng (2nd year PhD student in Chemistry)

Time and Location

Jun. 15 2023, Thursday, 4:00pm-5:00pm(Beijing Time), E207 (Education Building, 2^nd floor)

Language

English

Abstract

Numerous bioactive natural products and top-branded pharmaceuticals contain six-membered N-heterocyclic skeletons. In particular, the dearomatization reduction of pyridines and its homologous reductive access to a series of dihydropyridines (DHPs), dihydroquinolines (DHQs), and tetrahydroquinolines (THQs) and piperidines draw widespread interest since these azacycles can be key intermediates and/or structural motifs for these bioactive natural products and pharmaceuticals synthesis.

Selective double hydroelementation of N-heteroarenes can be one of the most straightforward and atom-economic routes toward dearomatized N-heterocycles bearing a (chiral) sp3 C−E bond (E = B, Si, etc.) at a specific site. Previously, Prof. Park and Chang found that B(C6F5)3 catalyzes double hydroboration and hydrosilylation of quinolines and/or pyridines via an outer-sphere mechanism involving a boronium or silylium ion. Although this boranecatalysis is highly regio- and diastereoselective with operational convenience, its inferior functional group tolerance and synthetic difficulty for chiral boranes have been pointed out as critical cons.

Herein, we developed a one-pot, site- and stereoselective borylative reduction of quinolines leading to a series of tetrahydroquinolines that possess an (enantioenriched) C(sp3)−B bond in the 4-position. A cationic Rh precatalyst [Rh(cod)2]OTf with a phosphine ligand DPEPhos enabled the borylative reduction of a range of quinolines with HBpin to provide the C4-borylated tetrahydroquinolines (THQ) in good to high yields under mild conditions. Based on the experimental observations, the reaction mechanism of the Rh-catalyzed borylative reduction cascade of quinoline was also proposed.

Biography

Ruibin Wang received his bachelor degree in Pharmaceutical Engineering from Qingdao University of Science and Technology, Then he moved to Sun Yat-sen University (Professor Gui Lu) and got Master degree (2011) in Medicine Chemistry. From February 2012 to July 2016, he worked in Chinese Academy of Sciences as a research fellow. Then, he moved to Guangdong Shunde Industrial Design Institute to work as department manager (2016-2020). In early 2020, He starts to pursue his PhD degree under the tutelage of Prof. Sehoon Park at Guangdong Technion Israel Institute of Technology (GTIIT) and Prof. Moris S. Eisen at Technion. Currently, his research is focused on the synthetic and mechanistic organometallic chemistry particularly involved hydroboration and hydrosilylation of N-Heteroarenes.