Chemoselective Conjugate Reduction of α,β-Unsaturated Ketones Catalyzed by Rhodium Amido Complexes in Aqueous Media

Abstract

Although a notable feature of Noyori's Ru-TsDPEN complex is that the transfer hydrogenation reaction is highly chemoselective for the C=O functional group and tolerant of alkenes, our early report indicated that the chemoselectivity could be switched from C=O to C=C bonds in the transfer hydrogenation of activated alpha,beta-unsaturated ketones. Now we have found that a variety of alpha,beta-unsaturated ketones, even without other electron-withdrawing functional groups, could be reduced on the alkenic double bonds with high selectivities employing amido-rhodium hydride complex in aqueous media, and up to 100% chemoselectivity has been achieved. It is notable that the chemoselectivity was improved significantly on going from organic solvent to water. Moreover, a 1,4-addition mechanism has been proposed on the basis of the corresponding experimental details and computational analysis.

Preparation, Hydrogen Bonds, and Catalytic Activity in Metal-Promoted Addition of Arylboronic Acids to Enones of a Rhodium Complex Containing an NHC Ligand with an Alcohol Function

“…36 Yellow oil. 1 H NMR (400 MHz, CDCl 3 ): δ 7.10−7.08 (m, 2H), 6.82−6.80 (m, 2H), 3.77 (s, 3H), 2.83 (t, J H−H = 7.5, 2H), 2.71 (t, J H−H = 7.5, 2H), 2.12 (s, 3H).…”

“…13 C NMR (100 MHz, CDCl 3 ): δ 207.5, 140.5, 128.1, 127.8, 125.7, 44.7, 29.6, 29.3. MS: m/z (%) 148 (100) [M + ], 133 (19), 105 (98), 91 (69), 79 (15), 78(14), 77 (23), 65 (12), 51(13).4-(Naphth-1-yl)butan-2-one (13b) 36. Yellow oil.…”

Efficient Synthesis of Functionalized 1-oxo-1-phenyl-2-acetic Acids through Ru(II)-catalyzed Transfer Hydrogenation

“…[12][13][14] With this background, we hypothesized that the Ru(II) catalyst could perform a specifically selective reduction of C=C bonds in strongly polar (E)-2-(1-oxo-1H-inden-2(3H)-ylidene)acetic acid via the transfer hydrogenation pathway, thereby providing the desired indanylacetic acid 2. To the best of our knowledge, this is the first report on the transfer hydrogenation of such compound using chiral TsDPEN-Ru(II) catalyst.…”

Homogeneous Chemoselective Hydrogenation of Heterocyclic Compounds – The Case of 1,4 Addition on Conjugated C-C and C-O Double Bonds of Arylidene Tetramic Acids

“…The hydride species (3) is usually formed from a catalyst precursor at the very beginning of the catalytic reaction and is not isolated itself (see below). A hydride migration (step II) affords the new unsaturated ruthenium species (5) to which dihydrogen coordinates (step III) affording the dihydrogen species (6). A substrate insertion (step I) and a hydride migration (step II) are usually very fast so only the product (7) can be observed.…”

“…[3][4][5] Many of them allow for the preferential reduction of carbon-carbon double bonds over a coexisting C=O functionality. [6][7][8][9][10][11] Catalysis is a multidisciplinary scientific concept that serves a broad range of industries covering specialty, fine, intermediate, commodity and life science chemicals. Catalysts are commonly used for the hydrogenation of alkenes, alkynes, aromatics, aldehydes, ketones, esters, carboxylic acids, nitro groups, nitriles and imines.…”