Asymmetric Reduction of α-Keto Aldoxime O-Ethers

Abstract

The catalytic asymmetric reduction of a-keto aldoxime O-methyl, O-benzyl, and O-trityl ethers, derived from substituted acetophenones, with borane/oxazaborolidines, by transfer hydrogenation, and with yeast, was studied. The reduction with borane/oxazaborolidines produced the corresponding a-hydroxy oxime ethers, a-hydroxy hydroxylamine ethers, and b-amino alcohols in 39-78% yields and up to 77% ee. The carbonyl group was selectively reduced by transfer hydrogenation with formic acid-triethylamine catalyzed by RhCl[(R,R)-TsDPEN](C 5 Me 5), and also with yeast, producing a-hydroxy oxime ethers, up to 75% ee and 93% ee, respectively.

Camphor‐Based Schiff Base Of 3‐Endo‐Aminoborneol (SBAB): Novel Ligand for Vanadium‐Catalyzed Asymmetric Sulfoxidation and Subsequent Kinetic Resolution

“…Given the more favorable chiral induction behavior of 3‐ endo ‐aminoborneol derivatives compared with that of 3‐ exo ‐aminoisoborneol derivatives in a few asymmetric transformations, we focused on forming new Schiff base ligands of 3‐ endo ‐aminoborneol and probing its chiral transformation property toward the vanadium catalyzed asymmetric sulfoxidation reaction. The synthesis of SBAB ligands (Scheme ) commenced with the SeO 2 oxidation of (1 R )‐camphor 22 to afford camphorquinone, 38 followed by monooxime preparation by reacting with hydroxylamine hydrochloride to obtain keto‐oxime 39 ( syn and anti diastereomeric ratio of 24:76), which was converted into >95 % anti isomer by refluxing it in water for 24 h. [17a, c] By using modified Bosiak's procedure, the keto‐oxime 39 was reacted with zinc in sodium hydroxide to undergo selective oxime reduction to provide 3‐ endo ‐aminoketone 40 …”

One-pot combination of enzyme and Pd nanoparticle catalysis for the synthesis of enantiomerically pure 1,2-amino alcohols

“…GC-MS (EI, 70 eV): m/z = 171 (M + , 1), 143(5), 141(16), 115 (4), 113 (13), 77 (100), 51(28), 50(14). The NMR data are in accordance with literature values 36. (S)-2-Amino-1-(4-chlorophenyl)ethanol [(S)-4b].67 mg (78%) off-white solid.…”

Vicinal difunctionalization of alkenes by four-component radical cascade reaction of xanthogenates, alkenes, CO, and sulfonyl oxime ethers

“…The functionalized α-keto oximes obtained herein should be useful scaffolds for further functionalization. Indeed, the α-keto oximes were reported to be used for the synthesis of a variety of synthetic intermediates, including functionalized keto-aldehydes [22], aminoalcohols [30], triazoles [31], just to name a few.…”