Synthesis of new chiral 2-functionalized-1,2,3,4-tetrahydroquinoline derivatives via asymmetric hydrogenation of substituted quinolines

Transfer Hydrogenation of Unsaturated Substrates by Half-sandwich Ruthenium Catalysts using Ammonium Formate as Reducing Reagent

“…Catalyst optimization for the transfer hydrogenation of nitriles (10), and Cp( i Pr 3 P)RuH 3 (11). Isolobal phosphine-and NHC-supported complexes 1-6 were examined at 0.5 mol % load at 70 8C ( Table 1, entries 1-6).…”

“…[1][2][3] For example, reduction of imines, nitriles, and N-heterocycles leads to amines which are important building blocks for the synthesis of numerous pharmaceutical products, agrochemicals, polymers, dyes, surfactants etc. [4][5][6][7][8][9][10][11] Traditionally, reduction of multiple bonds has been performed by soluble metal hydrides or by alkali metals dissolving in alcohols, which are expensive, hazardous and lead to large amounts of waste. [2,[12][13][14] Recently, there has been a significant progress in developing milder methods for reduction of nitriles and N-heterocycles based on catalytic hydrosilylation [12,[15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] and hydroboration.…”

(R)- and (S)-2,2′-Bis(diphenylphosphino)-6,6′-dimethoxy-1,1′-biphenyl

“…72 With the same type of catalyst, the hydrogenation of quinoline substrates with a COOR group in 2-position (R = alkyl, substituted alkyl) proceeded with moderate enantioselectivity (ee values up to 66%). 73 Enantiomeric excess values up to 94% were achieved with DIFLUORPHOS as the chiral diphosphine. 74 The same catalyst has been reported to promote the asymmetric hydrogenation of 7, The Ir-MeOBIPHEP-catalyzed asymmetric hydrogenation of quinolinium salts with Bronsted acids (e.g., TfOH.py) has been reported to afford the corresponding tetrahydroquinolines with 86% ee.…”

“…96 The performance of the MeOBIPHEP was also tested in an asymmetric domino allylstannylation-Heck reaction (eq 72). 97 No other atropisomeric ligand gave better results, and the highest enantiomeric ratio (98:2) was obtained in the presence of a ferrocenyl chiral ligand (Taniaphos [73][74][75]. The Cu-catalyzed 1,3-dipolar cycloaddition of glycine imine with nitroalkene led to a mixture of exo/endo-isomers, the enantiomeric excess being 90% for the endo-derivative (eq 73).…”

Substrate Activation in the Catalytic Asymmetric Hydrogenation ofN‐Heteroarenes

“…The authors do not provide any direct evidence of the participation of the acyl groups in the coordination sphere of the metal in the examples indicated in Scheme . However, the hydrogenation of derivatives analogous to the heterocycles indicated in Scheme (a, b), but without a chelating substituent, either did not proceed30 or led to hydrogenated products with lower enantioselectivity 35…”