Iodoimidazolinium-Catalyzed Reduction of Quinoline by Hantzsch Ester: Halogen Bond or Brønsted Acid Catalysis
Using a designed Josiphos ligand and a Hantzsch ester reductant, various allenes are reduced to the corresponding chiral terminal alkenes with high selectivities.
The reduction consists of formally transferring two hydrogen atoms from Hantzsch ester (HEH) to quinoline (QNL). As one may have expected, it is difficult for two hydrogens to transfer simultaneously in a concerted manner due to the rigid planar geometry of HEH .
Thiourea catalysed reduction of a-keto substituted acrylate compounds using Hantzsch ester as a reducing agent in water† Guanglin Weng,‡a Xiaobo Ma,‡a Dongmei Fang,b Ping Tan,a Lijiao Wang,a Linlin Yang,a Yuanyuan Zhang,a Shan Qian*a and Zhouyu Wang *a The ﬁrst method for the reduction of a-keto substituted acrylate compounds by Hantzsch ester in water
as Hantzsch ester, which has been used as an NADHmodel compound) in the presence of sodium or potassium alkoxide as well as Grignard reagent. These reductions were per-formed at refluxing temperature in benzene or dimethylformamide. However, the chemical yields were not always high, this being ascribed to partial hydrolysis of the ester groups of the
Hantzsch pyridine synthesis – overview The Hantzsch synthesis is a four-component reaction between an aldehyde, two equivalents of a β-ketoester and ammonia, …
Described herein are differences in behavior between a Hantzsch ester and a benzothiazoline as hydrogen donors in the chiral phosphoric acid catalyzed asymmetric reductive amination of ketones with p‐anisidine.The asymmetric reductive amination of ketones with a Hantzsch ester as a hydrogen donor provided the corresponding chiral amines exclusively, regardless of the structures of the .
The Hantzsch reaction discovered in 1889 remains one of the most reliable routes to thiazoles. This reaction generates one equivalent (equiv.) of hydrogen bromide, which can cause significant loss of optical purity with substrates prone to epimerization under …
Later on, Hantzsch 1,4-dihydropyridines, which mimic NADH reduction process in vitro, have shown promising biological activities. This review presents production procedure, major reactions of current interest, oxidation and reduction of Hantzsch 1,4-dihydropyridines, besides indication of some existing gaps and areas to be developed.
in the promotion of the enantioselective reduction of, -disubstituted nitroalkenes 1, 3, 4 with Hantzsch esters 10 [32 40]. Catalyst 5a, a thiourea resulting from the combination of an N,N-diethyl tert-butylglycinamide residue on one side and an elaborated trans-1,2-cyclohexanediamine on the
Borohydride reduction; Cyanide addition; Hemiacetal formation; Organometallic reagents; Grignard addition; Organolithium addition; Diastereoselective ketone reduction; Nucleophilic Substitution at C=O. Ester hydrolysis and transesterification; Amide formation from acid chloride; Acid Chloride Formation – …
Abstract. The exocyclic C=C double bond in phenacylideneoxindole and 2-oxoacenaphthen-1-ylidene ketone derivatives has been selectively reduced in good yields with a combination of the Hantzsch ester and zinc chloride in acetonitrile at ambient temperature.
Aug 18, 2019· A new method for the reduction of α -imino esters using Hantzsch ester is reported with chiral phosphoric acid (Scheme 4). A series of α -imino esters could be reduced to the corresponding α -amino esters in excellent yield with up to 94% ee.
Application Diethyl 1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate (DTP) was used to study the mechanism of electrochemical oxidation of DTP in ethanol/water solutions on a glassy carbon electrode.Used as a hydrogen source in organocatalytic reductive amination and conjugate reduction.
Hantzsch ester, a weak Brønsted acid, to quinoline prior to hydride reduction was identiﬁed as the key to the lowered energy barriers compared to other reaction pathways.
of an asymmetric reduction with newtypes of the chiral Hantzsch ester prepared in the pres-ent study, and a remarkable improvement in the reduction conditions and chemical yields for the asymmetric reduction of non-activated carbonyl compounds by using the 7V-anionized form of the chiral Hantzsch ester (1). RESULTS AND DISCUSSION
The amine moiety can be accessed by addition of Hantzsch ester to the reaction mixture. . A palladium-catalyzed reduction of 2-pyridinyl esters using hydrosilanes is applicable to the preparation of aliphatic, aromatic, and α,β-unsaturated aldehydes. Various functional groups, such as fluoro, methoxy, aldehyde, acetal, and ester, are tolerated.
A Quick Guide to REDUCTIONS IN ORGANIC CHEMISTRY . Hantzsch esters •LiAlH 4 . Allows for selective reduction of esters in the presence of carboxylic acids, amides and nitriles. Also reacts with aldehydes, ketones and epoxides. LiBH 4
An efficient catalyst-free reduction of aldimines is reported. In the absence of any additional catalysts, a series of N-aromatic aldimines were reduced with Hantzsch esters as the hydrogenation .
Of continuing value is the sodium metal-mediated Birch reduction of arenes (another name for aromatic hydrocarbons). Less important presently is the Bouveault–Blanc reduction of esters. The combination of magnesium and methanol is used in alkene reductions, e.g. the synthesis of asenapine:
effective for the selective reduction of N-(alkoxy(aryl) methyl) benzamide compounds to the corresponding benzamides. The reaction conditions, solvent effects, and reaction mechanism were discussed in the present work. Keywords N-(alkoxy(aryl)methyl)benzamide compounds Palladium on carbon Reduction Hantzsch ester 1,4-dihydropyridine 1 Introduction
The severe steric constraints of the tert-butyl adduct are rapidly overcome at 23°C (entry 9, 97% ee, 95% yield, 5 min). Importantly, this mild hydride-delivery method is compatible with functional groups that are often susceptible to reduction (e.g., aldehydes and halogens, entry 4, 92% yield, 97% ee).
NADH-like Hantzsch esters which makes the reaction seem to mimic bioc hemical reductions. Since the first report of enantioselective C=N bonds reduction using Hantzsch esters in the presence of Brønsted acids to afford amines with moderate enantioselectivities (up to 63 …
pressed their formation.16,22 Further reduction of the Hantzsch ester loading to 10 mol% led to lower reaction conversions (entry 5) using blue LED irradiation, however by
The use of imidazolidinone 2 as the asymmetric catalyst has been found to mediate the transfer of hydrogen to a large class of enal substrates from ethyl Hantzsch ester. The capacity of catalyst 2 to accelerate E-Z isomerization prior to selective E-olefin reduction allows the implementation of geometrically impure enals in this operationally .
species that in the presence of a suitable Hantzsch ester would undergo enantioselective hydride reduction, thereby allowing asym-metric reductive amination in an in vitro setting.9 This proposal was further substantiated by the significant advances in hydrogen-bonding catalysis, arising from the pioneering studies of Jacobsen,10
Jul 10, 2013· Hantzsch ester has also been employed as a stoichiometric reductant to achieve the desulfonylation of β-ketosulfones . 49 As in the reduction of phenacylsulfonium salts, the reaction likely proceeds via formation of Ru(bpy) 3 +, which may reduce the β-ketosulfone 34 to an α-carbonyl radical analogous to 14.
Hantzsch ester as reducing agent enables a cascade Knoevenagel condensation-reduction approach in water. Various reduced Knoevenagel adducts could be easily prepared by direct alkylation of malononitrile, ethyl 2-cyanoacetate, and 2-(4-nitrophenyl)acetonitrile, respectively.
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