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Hantzsch ester (HEH) is a bench‐stable compound used in hydrogenation and photoinduced reactions, where it acts as a photoreductant and an electron donor. In this study, we describe a new use of this classical reductant in the visible‐light‐induced desulfurative coupling of alkyl benzothiazolyl sulfides with electron‐deficient alkenes/alkynes via activation with base additives. C(sp3)─S scission is achieved through catalyst‐free HEH anion‐mediated reactions and organo‐photocatalysis. The synthetic utility is illustrated with several examples of derivatization of natural products, including monosaccharides. In addition, mechanistic investigations reveal that the HEH anion acts as a photoreductant in catalyst‐free reactions and as a sacrificial reductant in the organo‐photocatalysis. [ABSTRACT FROM AUTHOR]

The facile generation of the α‐acyloxy carboxamide radical is hereby reported for the first time, utilizing a photoredox catalyzed reaction of Passerini adducts synthesized using a 4‐formyl‐1,4‐dihydropyridine as the carbonyl component. This radical effectively engages in a Giese reaction with a range of olefins, ultimately leading to the synthesis of novel Passerini‐derived products not previously amenable to direct aldehyde‐based transformations. Consequently, the resulting strategy, developed both in batch and in flow, offers a promising opportunity to expand the chemical space accessible through the Passerini reaction, virtually incorporating "impossible" aldehydes. [ABSTRACT FROM AUTHOR]

A convenient and efficient method for the synthesis of optically active difluoro-substituted indoline derivatives starting from the corresponding 3H-indoles by chiral phosphoric acid-catalyzed transfer hydrogenation was developed. Using Hantzsch ester as the hydrogen source under mild reaction conditions, the target products can be obtained with excellent yield and enantioselectivity.

Comprehensive Summary: Hypochlorite (ClO–) is an important reactive oxygen species produced by the immune system to fight off invading pathogens, but its over‐expression can interfere with normal physiological process and induce serious diseases. Although a variety of molecular probes have been reported for detecting ClO–, the development of advanced fluorescent tools with faster response and higher sensitivity to precisely monitor ClO– remains a challenge. In this work, two Hantzsch ester (a derivative of 1,4‐dihydropyridine) derived fluorescent probes MeDHP‐BCl and MeDHP‐PhBCl were constructed based on asymmetric BODIPY‐matrix. These probes exhibit significant fluorescence turn‐on in the ultra‐sensitive (detection limit < 1 nmol/L) and ultra‐fast response (≤ 5 s) to ClO–. The reaction has been determined to be a highly selective N‐chlorination of Hantzsch ester which cannot be activated by various common bioactive species, including nitric oxide (NO) that could oxidize Hantzsch ester under aerobic physiological conditions in most reports. MeDHP‐PhBCl possessed a relatively longer fluorescence emission wavelength and higher quantum yield after activation, while more notably, MeDHP‐BCl displayed lower cytotoxicity and more remarkable fluorescence increment in the response to ClO–, enabling selective and precise visualization of endogenous ClO– over‐expression in living RAW264.7 cells. [ABSTRACT FROM AUTHOR]

C−H bond activation has surfaced as a transformative toolbox for the efficient assembly of biologically important molecules. However, despite of major advances in palladium, rhodium and silver catalysis, yet palladium(II)‐ catalyzed, iodobenzene diacetate (PIDA) mediated C−H bond activation in azole skeleton has deluged with interesting wining outcome. Concentrating on that we herein report on the involvement of 4‐functionalized 1,4‐dihydropyridines (R‐DHPs) as the representative surrogates of benzoyl, pivalyl and ethoxycarbonyl groups and in presence of PIDA it releases appropriate functional radical (following single electron transfer oxidation of R‐DHPs under thermal condition)to become the part of ortho‐ functionalized azoles via Pd(II) catalysis. In case of cyanation reaction, malononitrile has served the key source of nitrile functionality by undergoing oxidative C−CN bond cleavage in presence of PIDA and with the help of Pd(II) catalyst it offers ortho‐cyanated azoles. Additionally, the selective formation of C‐3 benzoyl and ester functionalized indazole derivatives in absence of Pd(II)‐catalyst and the unprecedented formation of homo‐coupling products between two identical 2H‐indazoles are also notable outcome of present strategic access. Overall this protocol operates under mild condition, tolerates a wide range of structural moieties and gives versatile azole derivatives in high efficiency. The antioxidant properties of the synthesized 2‐thiophenyl benzoyl selenazole and isoselenazole are further evaluated using a chemically defined method. The Copper‐ascorbate (Cu−As) was utilized as an oxidative stress generator. Out of screened azoles, the 2‐benzoyl isoselenazole compound (3 i) displays magnificent antioxidant property as compared to the 2‐thiophenyl benzoyl selenazole (3 g). [ABSTRACT FROM AUTHOR]

Visible‐light photoredox‐catalyzed metal‐free tandem one‐pot synthesis of 3,3‐disubstituted 3,4‐dihydroquinoxalin‐2(1H)‐ones from easily accessible 1,2‐diaminobenzenes, α‐ketoesters and 4‐alkyl Hantzsch esters has been described. This mild transformation affords the desired products in 47–93% yields for diversely decorated substrates, and can proceed on a gram‐scale. The efficacy of the current catalysis arises from the use of organic 1,2,3,5‐tetrakis(carbazol‐9‐yl)‐4,6‐dicyanobenzene (4CzIPN) as the photocatalyst and CF3CO2H as the additive. [ABSTRACT FROM AUTHOR]

Two photoreactions for the synthesis of 1- and 2-deoxysugars from thioglycosides were developed. In the presence of Hantzsch ester as an additive, a wide range of 1-deoxysugars were synthesized in moderate to excellent yields under irradiation with UV light without an exogenous photosensitizer. On the other hand, the utilization of 2,4,6-tri-tert-butylpyrimidine (TTBP) as the additive furnished a variety of 2-deoxysugars as the main products from their corresponding thioglycosides. The reported methodology has a broad substrate scope and high functional group tolerance and is scalable to gram-scale reaction. [ABSTRACT FROM AUTHOR]

An efficient photocatalytic synthesis of phenanthridines mediated by an organo‐photoredox initiator Hantzsch ester has been developed via denitrogenative intramolecular annulation of benzotriazolyl chalcones. The highly reducing photoactivated Hantzsch ester facilitates the transformation of benzotriazolyl chalcones into phenanthridinyl chalcones through photoinduced electron transfer (PET) and hydrogen atom transfer (HAT) processes. The mild reaction conditions utilizing inexpensive Hantzsch ester as photosensitizer, wide reaction scope and excellent functional group tolerance are notable attributes of the methodology. [ABSTRACT FROM AUTHOR]

Diethyl 2,6‐dimethyl‐1,4‐dihydropyridine‐3,5‐dicarboxylate (HEH) has been utilized as a visible‐light photoredox catalyst for the cross coupling of arylhalides and arylsulfinates without transition metal, sacrificial agent, and mediator. This method is compatible with various functional groups and provides diaryl sulfones in good to high yields. Mechanistic studies indicate that this reaction undergoes the stepwise light irradiation of HE−, single electron transfer (SET) in donor–acceptor complex (DAC) from *HE− to arylhalide, trapping of aryl radical with sulfinate, and SET oxidation of sulfone radical anion by HE. to sulfone by the DAC method. [ABSTRACT FROM AUTHOR]

• The electrocatalyst has a PtCo@Pt core-shell structure. • PtCo nanoparticles were encapsulated in a Pt shell using an organic hydride donor. • PtCo@Pt with the unique Pt shell demonstrates enhanced catalytic activity. • PtCo@Pt performed well in both half- and single-cell system tests. Platinum alloys with other transition metals are widely used as catalysts as a promising strategy to improve the activity. However, the vulnerability of transition metals to the liquid electrolyte and fuel gases present during the device operation results in degradation of the catalytic activity. Highly stable catalyst is achieved by encapsulating the carbon-supported PtCo intermetallic core nanoparticles in a robust Pt shell. The hydride from Hantzsch ester reduces the residual Cl on the surface of the Pt skeleton and slowly forms negatively charged defect sites without damaging the core structure. Then, a secondary Pt reduction reaction via the hydride is employed to cover the activated surfaces of the Pt skeleton to optimize the shell thickness without the formation of isolated Pt nanoparticles. The PtCo@Pt with the unique Pt shell shows higher catalytic activity and durability than commercial Pt/C for oxygen reduction reaction electrocatalysts in proton exchange membrane fuel cells. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Catalyst-free dehalogenation of a-haloketones under visible light irradiation is studied. The reactions were carried out in common organic solvent. The outcomes of dechlorination are excellent in yields up to 92%, and it is also applicable to bromides, which give even higher yields. The reaction is tolerable to a broad spectrum of substrates, especially to aromatic ketones, including various aryl and hetaryl groups. There are two examples of aliphatic ketones presented in the paper, although their reactivities are not as high as that of the aromatic ketones. [ABSTRACT FROM AUTHOR]

Disclosed herein is an expedient synthesis of biologically important isoindolinone derivatives from reactions of 2-formylbenzoic acids with various amines. This method operates via a deliberately designed catalyst-free tandem reductive amination/cyclization cascade event triggered by a transfer hydrogenation process with easily available Hantzsch ester as the organic hydride source. The ease of operation, mild reaction conditions, facile accessibility of the starting materials, and easy scalability of the current method distinguish it from the other precedent protocols, thus enable it a practical approach to the syntheses of valuable isoindolinone-incorporated drugs. [ABSTRACT FROM AUTHOR]

The asymmetric hydrogenolysis of racemic 3-substitued-3-hydroxyisoindolin-1-ones has been developed employing SPINOL-derived phosphoric acid and a high steric demand Hantzsch ester as the hydrogen source. The corresponding products are obtained in good yields and up to 93% enantioselectivities. [ABSTRACT FROM AUTHOR]

Abstract: Substituted Hantzsch esters can act as radical reservoirs in photoredox reactions, steadily releasing a carbon radical and a hydrogen atom radical in the absence of an additional electron acceptor. We propose that radical release by substituted Hantzsch esters occurs via a mechanism involving an internal redox cycle. Cinnamidecinnamides, styrenes, α,β‐unsaturated acids, and diarylethenes could be alkylated smoothly with these reagents. [ABSTRACT FROM AUTHOR]

• Treatment of 2,6-dimethyl-3,5-dicarboethoxy-4-(2-methoxyphenyl)-1,4-dihydropyridine (1) with i -PrMgBr, followed by D 2 O, workup, and recrystallization gave the starting dihydropyridine 1. NMR analysis of product indicated that no metalation had occurred at the C-2 and C-6 methyl positions (no deuterium incorporation at the C-2 and C-6 methyl positions and any other position in the molecule). Moreover, no addition products resulting from nucleophilic attack of Grignard reagent at either or both of the ester groups of 1 were observed. As a result, ester groups are tolerated and i -PrMgBr cannot be used as a strong base for C-deprotonation of classical Hantzsch esters. • Treatment of 2-bromomethyl-1,4-dihydropyridine derivative 2 with i -PrMgBr Grignard reagent at mild reaction condition furnished the organomagnesium reagents of Hantzsch esters through the halogen-magnesium exchange reaction with ester groups tolerance. • Trapping the magnesiated 1,4-dihydropyridine 2 with hard electrophile methyl iodide gave the major N-methylated product 6 and minor pyridine derivative 7. • In trapping the magnesiated reaction mixture with ethyl bromide, pyridine derivative 8 (15%) and dimer 9 (20%) could be separated. • N-Methylated product 6 and dimer 9 could be obtained through the intermediacy of dimagnesiated spiece 3. • The aromatization of dihydropyridine ring and formation of pyridine derivatives 7 and 8 could be occurred through the hydrolysis of organomagnesium derivative 5 or reaction of it with EtBr electrophile, respectively. • Iron-catalyzed cross-coupling reaction of 2 with allylMgBr, i -PrMgBr, and n-BuMgBr Grignard reagents afforded unsymmetrical 1,4-dihydropyridine Hantzch esters 10a-c in good yields. • Since the presence of N H bond of Hantzsch dihydropyridines is essential for the pharmaceutical effects of this class of compounds, thus, by using of this procedure, it is possible to prepare unsymmetrical 1,4-DHPs without protecting the N H group. The mild bromine-magnesium exchange reaction using i -PrMgBr in THF on the 2-bromomethyl-1,4-dihydropyridine Hantzsch esters allowed the synthesis of highly functionalized magnesiated 1,4-dihydropyridines with ester groups tolerance. Treatment of the resulting anionic intermediates with hard electrophile methyl iodide gave N-methylated product 6 and pyridine derivative 7 in 60 % and 10 % yields, respectively. In trapping the reaction mixture of magnesiated 1,4-dihydropyridine with ethyl bromide, pyridine derivative 8 , and dimer 9 were obtained. Also, FeCl 3 -catalyzed cross-coupling reaction of allylMgBr, i -PrMgBr, and n -BuMgBr Grignard reagents with 2-bromomethyl-1,4-dihydropyridine derivative 2 afforded unsymmetrical 1,4-dihydropyridine derivatives 10a-c in good yields. [Display omitted] [ABSTRACT FROM AUTHOR]

Synthesis of poly-substituted 3-hydroxy-2-oxindole-pyridine hybrids is reported via sp 3 C H bond functionalization as key steps using FeWO 4 nanoparticles as reusable heterogeneous catalyst. Formation of Hantzsch ester (DHP) followed by aromatization, and sp 3 C H bond functionalization was achieved using FeWO 4 nanoparticles (20 mol%) at 80 °C. Temperature dependent reactivity was observed for mono aldol (at 80 °C) and bis aldol (at 120 °C) products. The catalyst was regenerated and reused up to 6 cycles without losing catalytic activity. The FeWO 4 nanoparticles were also used for oxidative aromatization of different DHP derivatives and for the sp3 C H functionalization of 2-methyl pyridine. [ABSTRACT FROM AUTHOR]

The alkoxyl radical is an essential and prevalent reactive intermediate for chemical and biological studies. Here we report the first donor-acceptor complex-enabled alkoxyl radical generation under metal-free reaction conditions induced by visible light. Hantzsch ester forms the key donor-acceptor complex with N-alkoxyl derivatives, which is elucidated by a series of spectrometry and mechanistic experiments. Selective C(sp3)-C(sp3) bond cleavage and allylation/alkenylation is demonstrated for the first time using this photocatalyst-free approach with linear primary, secondary, and tertiary alkoxyl radicals. [ABSTRACT FROM AUTHOR]

A simple and readily available cyclopentadiene-based Brønsted acid was employed to catalyze the transfer hydrogenation of 2-substituted quinolines using Hantzsch ester as the hydrogen source. This conceptually new designed organocatalyst demonstrates remarkably high efficiency for this transformation and a variety of substituted 1,2,3,4-tetrahydroquinoline derivatives were afforded in excellent yields under mild reaction conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] We report a photochemical approach for the generation of alkyl radicals from alkylsilyl peroxides (ASPs) in the absence of any transition metal or photocatalyst. This operationally simple protocol utilizes Hantzsch ester as a photoreductant to efficiently induce the O O bond cleavage of various ASPs via single-electron transfer, generating the corresponding alkyl radicals under mild conditions. The radicals generated by this method participate in a Giese-type addition with a wide range of electron-deficient alkenes. This study broadens the methods by which radicals can be generated from ASPs, and thus improves their applicability and versatility in the field of radical chemistry. [ABSTRACT FROM AUTHOR]

Thermodynamic driving forces of eight possible elementary steps for Hantzsch ester and six possible elementary steps for H2 to release two hydrogen atoms (2H•) or ions (H− and H+) in acetonitrile were examined using experimental method or the available related thermodynamic data for the first time, which can facilitate chemists to choose a suitable reducing agent between Hantzsch ester and H2 to reduce a given organic unsaturated compound in acetonitrile and make a rational diagnosis on the detailed reaction mechanisms. The focus of this paper is to compare the differences between Hantzsch ester and H2 to release two hydrogen atoms (or ions) on the thermodynamics of elementary steps in acetonitrile. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Hantzsch esters are used extensively in photoredox catalysis as terminal reductants, donating an electron and a hydrogen atom. They generally exert their reducing potential by means of single-electron transfer to a photoredox catalyst, which acts as an electron shuttle. Recently, they were found to effect single-electron transfer upon visible-light irradiation in the absence of a photocatalyst. We found that this ability could be used for debromination of vicinal dibromo compounds to afford alkenes, as well as for hydrodifluoroacetamidation reactions. We also found that substituted Hantzsch esters could be used as reductive alkylation reagents to build highly congested ketones. [ABSTRACT FROM AUTHOR]

The photoredox catalytic coupling of halomethyl arenes to bibenzyl derivatives has been demonstrated. The catalytic protocol employed the Hantzsch ester, potassium phosphate, and a photoactive cyclometalated IrIII complex catalyst. A photochemical quantum yield as high as 20 % was obtained. The catalytic mechanism was investigated in detail by performing photophysical and electrochemical measurements, as well as by quantum chemical calculations. The results suggest that two-electron mediation might be responsible for the improved photon economy. The reaction protocol was compatible with halomethyl arenes that contain a variety of functional groups. Finally, the synthetic utility of our protocol was demonstrated by the preparation of a natural dihydrostilbenoid, brittonin A. [ABSTRACT FROM AUTHOR]

A water soluble Hantzsch ester derivative of coumarin, DHPS , was synthesized and successfully applied in the fluorescent sensing nitric oxide (NO) in aqueous solution. The fluorescence of probe DHPS is extremely weak, while its fluorescence was greatly switched on upon the addition of NO solution and showed high selectivity and sensitivity to NO. The limitation of the detection was calculated to be 18 nM. The NO-induced aromatization of dihydropyridine in DHPS to pyridine derivative ( PYS ) proved to be the switching mechanism for the fluorescent sensing process, which was confirmed through spectra characterization and computation study. Cytotoxicity assay demonstrated both DHPS and PYS are biocompatible, the DHPS was successfully applied to track the endogenously produced NO in the RAW 264.7 cells. [ABSTRACT FROM AUTHOR]

Given its synthetic relevance, the catalytic enantioselective reduction of β,β-disubstituted nitroalkenes has received a great deal of attention. Several bio-, metal-, and organo-catalytic methods have been developed, which however are usually applicable to single classes of nitroalkene substrates. In this paper, we present an account of our previous work on this transformation, which implemented with new disclosures and mechanistic insights results in a very general protocol for nitroalkene reductions. The proposed methodology is characterized by (i) a remarkably broad scope encompassing various nitroalkene classes; (ii) Hantzsch esters as convenient (on a preparative scale) hydrogen surrogates; (iii) a simple and commercially available thiourea as catalyst; (iv) user-friendly procedures. Overall, the proposed protocol gives a practical dimension to the catalytic enantioselective reduction of β,β-disubstituted nitroalkenes, offering a useful and general platform for the preparation of nitroalkanes bearing a stereogenic center at the β-position in a highly enantioenriched form. A transition state model derived from control kinetic experiments combined with literature data is proposed and discussed. This model accounts and justifies the observed experimental results. [ABSTRACT FROM AUTHOR]

The debromination of vicinal dibromo compounds to generate alkenes usually requires harsh reaction conditions and the addition of catalysts. Just recently the visible-light-induced debromination of vicinal dibromo compounds emerged as a possible alternative to commonly used methods, but the substrate scope of this reaction is limited and a photocatalyst is necessary for the successful conversion of the starting compounds. A catalyst-free visible-light-induced debromination of vicinal dibromo compounds with a base-activated Hantzsch ester as photosensitizer is reported. The method has a wide substrate scope and a broad functional-group compatibility. [ABSTRACT FROM AUTHOR]

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 ketones, whereas a similar transformation with a benzothiazoline provided chiral amines and p-methoxyphenyl-protected primary amines in variable yields, depending on the structures of both the ketones and benzothiazolines. Because a benzothiazoline has an N,S-acetal moiety that is vulnerable to p-anisidine, the primary amine can be formed through transimination of the benzothiazoline with p-anisidine followed by reduction of the resulting aldimine with remaining benzothiazoline. [ABSTRACT FROM AUTHOR]

A screening platform, which offers a highthroughput approach as well as an easy investigation of kinetic isotope effects, applicable to a wide range of reactions is presented. To illustrate the high potential of this approach, the asymmetric transfer hydrogenation of methyl benzoylformate with copper(II) bis(oxazoline) and Hantzsch ester was examined. Accordingly, the enantioselectivities of the reaction performed on-column in a microcapillary were comparable to standard reaction conditions, however, we were able achieve catalysis and analysis in a single step in less than 30 min. The throughput can be increased by simultaneous investigation of different substrates without increasing the overall analysis time. Use of di-deuterated Hantzsch ester allowed us to investigate the kinetic isotope effect of the transfer hydrogenation reaction only requiring a minute amount of the deuterated transfer hydrogenation reagent. Hence we were able to get further insights into the mechanism of the asymmetric transfer hydrogenation using Hantzsch ester as hydrogen source. The here presented technique is broadly applicable to study isotope effects on a very small scale, which is a rapid and an inexpensive alternative compared to conventional experiments. [ABSTRACT FROM AUTHOR]

A facile route to 1-alkyl-2-naphthols/phenols via deamination followed by a metal-free catalytic transfer hydrogenation of 1-(α-aminoalkyl)-2-naphthols/phenols, commonly called Betti bases under microwave irradiation has been developed. Hantzsch 1,4-dihydropyridine is used as the reductant. A mechanistic proposal involving elimination–addition mechanism is described. The reaction is simple, clean, and offers very good yields of products. [ABSTRACT FROM AUTHOR]

The ‘template’ polyborate BOROX catalysts are shown to mediate the asymmetric transfer hydrogenation of 2-quinolines. The rapid and simple generation of a large family of BOROX catalysts with significantly altered asymmetric pockets is described. A transition state model that explains the enantioselectivity is proposed. [ABSTRACT FROM AUTHOR]

A highly efficient transfer hydrogenation of quinolines with Hantzsch ester as hydrogen source in the presence of 1 mol% Fe(OTf) 2 under mild conditions has been developed. A series of substituted 1,2,3,4-tetrahydroquinoline derivatives were afforded in excellent yields with good functional group tolerance. [ABSTRACT FROM AUTHOR]

Poor solubility of Hantzsch ester is used as indicator in the reduction of methylidene malononitrile. The Knoevenagel reaction is integrated to develop a reductive alkylation of malononitrile with aryl and aliphatic aldehyde as the carbonyl substrate. [ABSTRACT FROM AUTHOR]

2,6-Dimethyl-3,5-bis(ethoxycarbonyl)-1,4-dihydropyridine (dihydropyridine Hantzsch ester, DHPHE) and CuSO4 · 5H2O efficiently accelerated azide–alkyne cycloaddition reactions of both aliphatic and aromatic substrates and gave 1,4-disubstituted 1,2,3-triazoles as the only isomer in good to excellent yields at room temperature with 1 mol% of CuSO4 · 5H2O/DHPHE (1:1 in molar ratio). The reaction could be carried out smoothly in methanol in air with high efficiency. DHPHE may play multiple important roles in the reaction: a reducing reagent to generate the catalytic center copper(I) from CuSO4, a base to help form the intermediate acetylide, and a ligand to stabilize the catalytic copper(I) species via coordination after being transformed to pyridine derivative. [Supplementary materials are available for this article. Go to the publisher's online edition ofSynthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.] [ABSTRACT FROM AUTHOR]

Abstract: A new type of water-soluble polymer-supported NADH co-enzyme model-PAA (polyacrylic acid)-supported Hantzsch 1,4-dihydropyridine ester (PAA–HEH) was designed and synthesized. Catalytic amount of the supported reagent was used in the hydrogenation of α,β-epoxy ketones to the corresponding β-hydroxy ketones and showed great catalytic efficiency in the reduction reaction. This PAA–HEH was an optimal potential for recycling use. [Copyright &y& Elsevier]

Abstract: An efficient and practical protocol for the reduction of aldimines, ketimines, and α-imino esters in the presence of catalytic amount of molecular iodine with Hantzsch ester at ambient temperature afforded the corresponding amines in excellent yields. [Copyright &y& Elsevier]

Abstract: Diastereoselective reduction of gem-difluorocyclopropenyl ketones was accomplished by their Brønsted acid catalyzed reactions with the non-metal based hydride transfer reagent, Hantzsch ester (diethyl 1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate) (HEH). The high yield reactions produced a significantly cis-enriched product mixture, from which the cis-isomer could be readily separated by column chromatography. [Copyright &y& Elsevier]

Catalytic hydrogenation of 2-cyano-2-(2-nitrophenyl)acetates bearing an electron withdrawing substituent to the nitrile, using Hantzsch ester catalyzed by Pd/C, affords 2-aminoindoles in good to excellent yields. [ABSTRACT FROM AUTHOR]

Abstract: The reduction of conjugated nitroalkenes into nitroalkanes with Hantzsch ester using S-benzyl isothiouronium chloride as a recoverable organocatalyst was successfully accomplished with high yield and excellent chemoselectivity. [Copyright &y& Elsevier]

Abstract: Based on our recently developed step-economic methodology of reductive alkylation of lactams/amides, we have developed a two-step synthesis of azasugar radicamine B (2a) and a four-step synthesis of azasugar hyacinthacine A3 (5) from the common chiral building block 12. Hantzsch ester (HEH) was used as a milder hydride donor in the one-pot stereoselective reductive alkylation of lactam 12. The Wacker oxidation of fully substituted pyrrolidine derivative 2,5-trans-17 led to the synthesis of hyacinthacine A3 (5). Compound 2,5-trans -17 could also serve as a plausible key intermediate for the synthesis of broussonetine sub-class of azasugars. [Copyright &y& Elsevier]

Abstract: A new class of organocatalysts based on the structure of 2,3-dihydrobenzo[1,4]oxazine was prepared and applied in the enantioselective transfer-hydrogenation of α,β-unsaturated aldehydes with Hantzsch ester as hydride donor. These catalysts proved to be particularly effective for the conjugate reduction of β,β-diaryl-substituted acrylaldehydes leading to saturated aldehydes bearing a stereogenic center with two different aryl groups with enantioselectivities of up to 91% ee. [Copyright &y& Elsevier]

Abstract: An InCl3 catalyzed efficient synthesis of novel dispiro[cyclopent-3′-ene]bisoxindoles is accomplished via a one-pot reductive cyclization of isatylidene malononitriles using the Hantzsch ester. [Copyright &y& Elsevier]

A thiourea-catalyzed biomimetic reduction of conjugated nitroalkenes has been developed. Various aromatic and aliphatic conjugated nitroalkenes can be reduced to give the respective nitroalkanes with good yields under mild conditions. This protocol is not only practical, but may also provide insight into the mechanisms of redox transformations in biological systems. [ABSTRACT FROM AUTHOR]

Abstract: An efficient metal-free procedure for the synthesis of tertiary amines by the reductive amination of carbonyl compounds is reported, which allows a convergent access to sterically hindered amines of the general formulas NR(R′)2 and NRR′R″. The mild and operationally simple protocol uses the Hantzsch ester for transfer hydrogenation and catalytic amounts of thiourea for imine activation. [Copyright &y& Elsevier]

Abstract: A novel and green approach for the two-carbon homologation of aldehydes using amino acid catalysis has been developed and further extended to the generation of pharmaceutically active cyano-esters via four-component reactions in one-pot. [Copyright &y& Elsevier]

[Display omitted] An efficient and practical method for chemoselective "on-water" reduction of α-keto amide by Hantzsch ester without using any catalysts and additives was developed. Control experiments indicated that the intramolecular hydrogen bond of α-keto amide was crucial for this transformation. A variety of α-hydroxy amides were prepared in high yields in an environmentally friendly way. [ABSTRACT FROM AUTHOR]

The one-pot reaction of aldehydes, triacetic acid lactone, and Hantzsch 1,4-dihydropyridine affords 3-alkyl pyrones via a reductive alkylation strategy. [ABSTRACT FROM AUTHOR]

[Display omitted] An isothiouronium organocatalyst prepared from thiourea was first employed to catalyze the transfer hydrogenation of various 2-alkyl and arylquinolines with Hantzsch ester as the hydrogen source. This metal-free catalyzed reduction of 2-substituted quinoline efficiently rendered good to excellent yields of tetrahydroquinolines under mild conditions with a small amount of catalyst (5 mol%). [ABSTRACT FROM AUTHOR]