Enantioselective Synthesis of Boryl Tetrahydroquinolines via Cu-Catalyzed Hydroboration

Abstract

A Cu-catalyzed regio- and enantioselective hydroboration of 1,2-dihydroquinolines with high yields and excellent enantioselectivities (up to 98% ee) was presented. This method could be applied in the asymmetric synthesis of the important intermediates used in the enantioselective synthesis of the potential agent Sumanirole for the treatment of Parkinson's disease and of the potentially interesting positive inotropic agent (S)-903.

Enantioselective Synthesis of 4-Aminotetrahydroquinolines via 1,2-Reductive Dearomatization of Quinolines and Copper(I) Hydride-Catalyzed Asymmetric Hydroamination

“…This is largely due to the difficulties associated with resonance stabilization caused by aromaticity. Inspired by the elegant examples of stepwise reduction/enantioselective catalysis, we therefore used a sequence as an alternative strategy, namely, 1,2-reductive dearomatization of quinolines followed by copper hydride-catalyzed asymmetric hydroamination of the resultant 1,2-dihydroquinolines. Nevertheless, this method would be very challenging since the internal cis -cyclic alkenes are well-known as challenging and problematic substrates in enantioselective hydroamination catalyzed by copper hydride…”

Catalytic Enantioselective Construction of Chiral Benzo-Fused N -Heterocycles through Friedel–Crafts-Type Electrophilic Chlorination

“…72,73 In addition, reducing the catalyst loading led to the decrease of the yield of the product (entry 16). It should be noted that acids played an important role in the reactions (entries [17][18][19][20][21][22]. For example, when BF 3 •OEt 2 was used, both the yield and the enantioselectivity were significantly decreased.…”

“…However, the methods developed usually suffer from the functionalization of only specific functional groups at the 2-, 3-, or 4-position of the tetrahydroquinolines formed, the scarcity of materials, and the unsatisfactory enantioselectivity of the reactions (Figure 1a). [14][15][16][17][18][19][20][21][22][23][24][25][26][27] On the other hand, it remains difficult to produce benzo-fused N-heterocycles with more rings, such as chiral polycyclic rings using the current systems. 28,29 Therefore, it is desirable to develop efficient methods to synthesize diverse chiral benzo-fused N-heterocycles from readily available substrates.…”

Mild, Metal-Free Oxidative Ring-Expansion Approach for the Synthesis of Benzo[b]azepines

“…Based on this criterion, we herein describe a general methodology for the straightforward synthesis of benzo [b]azepines by a novel, mild and metal-free oxidative C−H bond functionalization/ring expansion tandem reaction from readily available dihydroquinolines (see Scheme 1C). We started our screening with N-methylcarboxylate dihydroquinoline (1a) 12,13 as a model substrate for the optimization of the reaction conditions of the metal-free ring expansion with TMSCHN 2 (Table 1; see the Supporting Information (SI) for a complete screening).…”

“…We started our screening with N -methylcarboxylate dihydroquinoline ( 1a ) , as a model substrate for the optimization of the reaction conditions of the metal-free ring expansion with TMSCHN 2 (Table ; see the Supporting Information (SI) for a complete screening).…”