一个简单、环境友好的硅胶固载硫酸催化Biginelli反应体系(英文)

A protocol for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones and-thiones was developed by means of a three-component condensation of an aldehyde,a β-dicarbonyl compound,and urea or thiourea in acetic acid catalyzed by silica-bonded S-sulfonic acid.Compared to the classical Biginelli reaction conditions,this new protocol has the advantages of consistently excellent yields and short reaction times.After the reaction,the catalyst could be recovered easily and reused with little change in its activity.     

DFT Study on the Origin of the Enantioselectivity of （S）-4-Hydroxylproline-Catalyzed Direct Aldol Reaction between Acetone and 4-Nitrobenzaldehyde

DFT-B3LYP calculations were carried out to study the enantioselectivity of the （S）-4-hydroxylproline-catalyzed direct aldol reaction between acetone and 4-nitrobenzaldehyde. Four transition structures associated with the stereo-controlling step of the reaction have been determined. They are corresponding to the anti and syn arrangements of the methylene moiety related to the carboxylic acid group in enamine intermediate and the si and re attacks to the aldehyde carbonyl carbon. The effect of DMSO solvent on the stereo-controlling step was investigated with polarized continuum model （PCM）. The computed energies of the transition states reveal the moderate enantioselectivity of the reaction.     

磺化碳催化Biginelli反应一锅法合成3,4-二氢-2(1H)-酮和硫酮(英文)

A sulfonated carbon material was shown to be a highly efficient,eco-friendly,and recyclable solid acid catalyst for the Biginelli reaction of β-ketoester,aldehyde,and urea or thiourea under solvent-free conditions.It gave 3,4-dihydropyrimidin-2(1H)-ones and-thiones in good to excellent yields.This method has the advantages of a simple procedure with easy work-up,short reaction time,and high yields.The catalyst can be recycled after a simple work-up and was reused four times without substantial reduction in activity.     

硅胶键合的N-丙基三亚乙基四胺氨基磺酸作为可回收固体酸催化剂催化合成2-氨基-4,6-二芳基烟腈(英文)

A simple and efficient procedure for the preparation of silica-bound N-propyl triethylenetetramine sulfamic acid(SBPTETSA) by the reaction of silica-bound N-propyl triethylenetetramine(SBPTET) with chlorosulfonic acid in chloroform is described.Silica-bound N-propyl triethylenetetramine sulfamic acid was employed as a recyclable catalyst for the synthesis of 2-amino-4,6-diarylnicotinonitriles from the multi-component reaction of an acetophenone derivative,an aromatic aldehyde,malononitrile,and ammonium acetate under solvent-free conditions at 100 °C.The heterogeneous catalyst was recycled for five consecutive runs in the optimized multi-component reaction of 4-chloroacetophenone,4-chloroenzaldehyde,malononitrile,and ammonium acetate without significant loses to its catalytic activity.     

An efficient green synthesis of dispirohydroquinolines via a diastereoselective one-pot eight-component reaction

The one-pot eight-component reaction between Meldrum's acid, an aromatic aldehyde, and an aryl amine was achieved in the presence of citric acid catalyst. The corresponding dispirohydroquino-lines were obtained in good yields with excellent diastereoselectivity. This method is a combination of the Knoevenagel and Michael reactions.     

One-step Synthesis of ε-Caprolactam by the Liquid Phase Nitrosation of Cyciohexane over the Catalysts Containing CH3COO-or-COOH

ε-Caprolactam（CL or CPL） is one of the most important intermediates used in polymer industry for the production of several million tons of nylon-6 every year^[1]. All current commercial processes for the production of caprolactam are based on either benzene or tolueneI21. Caprolactam is synthesized by the Beckmann rearrangement of cyclohexanone oxime with fuming sulfuric acid or sulfuric acid as the reaction medium, and cyclohexanone oxime is produced by the reaction between cyclohexanone and hydro- xylamine（only one exception is the Toray PNC process）.     

Synthesis of （2R,3aR,8aR）-6-Chloro-3a-hydroxy-1,2,3,3a,8,8a-hexahydropyrrolo[2,3-b]indole-2-carboxylic Acid Methyl Ester by Reductive Cyclization

A synthesis of (2R，3aR，8aR)-6-chloro-3a-hydroxy-1,2,3,3a,8,8a-hexahydropyrrolo[2,3-b]indole-2-carboxylic acid methyl ester (1) was achieved. An aldol reaction with Garner aldehyde, a hydroxyl introduction by Davis reagent, and a reductive intramolecular ring-closure reaction were served as the key steps. This piece of work provides a new way to synthesize the analogues of hexahydropyrrolo[2,3-b]indole, starting from readily available chemical substrates and inexpensive reagents.     

Ferric Perchlorate Catalyzed One‐pot Synthesis of 1,2,3,4‐Tetrahydro‐2‐pyrimidinones and ‐thiones: an Expedient Protocol for the Biginelli Reaction

An efficient synthesis of 1,2,3,4-tetrahydro-2-pyrimidinones and -thiones using ferric perchlorate as the catalyst from an aldehyde, ethyl acetoacetate, and urea or thiourea in acetonitrile was described. Compared to the classical Biginelli reaction conditions, this new method consistently has the advantage of full catalysis, good yields and short reaction time.     

无溶剂条件下用于合成3,4-二氢嘧啶-2(1H)-酮的高效、可磁性回收Fe_3O_4纳米粒子催化剂(英文)

The catalytic activity of Fe3O4 nanoparticles (NPs) in a one-pot three component condensation reaction consisting of an aromatic aldehyde, urea or thiourea, and a β-dicarbonyl under solvent-free conditions was investigated. This reaction affords the corresponding dihydropyrimidinones (thiones) in high to excellent yields. Compared with the classical Biginelli reactions this method consistently gives a high yield, easy magnetic separation, a short reaction time, and catalyst reusability.     

过氧化氢溶液中单和双金属金-银纳米粒子氧化L-亮氨酸的动力学(英文)

The catalytic activity of surfactant stabilized mono-and bimetallic Au and Ag nanoparticles for the oxidation of an amino acid,L-leucine,was studied using hydrogen peroxide as the oxidant.The Au and Ag nanoparticle catalysts exhibited very good catalytic activity and the kinetics of the reaction were found to be pseudo-first order with respect to the amino acid.The effects of several factors,such as oxidant concentration,ionic strength,pH,and catalyst concentration on the reaction,were also investigated.In particular,optimal oxidant and catalyst concentrations were determined.Very high concentrations of the metal nano-catalysts or the oxidant led to a dramatic increase in reaction rate.Moreover,bimetallic Au-Ag catalysts provided higher selectivity than pure Au or Ag.     

Efficient Pictet–Spengler Bioconjugation with N‐Substituted Pyrrolyl Alanine Derivatives

We discovered N‐pyrrolyl alanine derivatives as efficient reagents for the fast and selective Pictet–Spengler reaction with aldehyde‐containing biomolecules. Other aldehyde‐labeling methods described so far have several drawbacks, like hydrolytic instability, slow reaction kinetics or not readily available labeling reagents. Pictet–Spengler cyclizations of pyrrolyl 2‐ethylamine substituted at the pyrrole nitrogen are significantly faster than with analogues substituted at the α‐ and β‐ position. Functionalized N‐pyrrolyl alanine derivatives can be synthesized in only 2–3 steps from commercially available materials. The small size of the reagent, the high reaction rate, and the easy synthesis make pyrrolyl alanine Pictet–Spengler (PAPS) an attractive choice for bioconjugation reactions. PAPS was shown as an efficient strategy for the site‐selective biotinylation of an antibody as well as for the condensation of nucleic‐acid derivatives, demonstrating the versatility of this reagent.     

Molecular level understanding of the role of aldehyde in vegetable‐aldehyde–collagen cross‐linking reaction

The role of formaldehyde (HCHO) in vegetable‐aldehyde–collagen cross‐linking reaction was investigated at the B3LYP/6‐31+G(d) level, where lysine (LYS) was used as model of collagen and catechin (EC) as model of condensed vegetable tannin. Atomic charge and Frontier molecular orbital analysis show that intermediates formed by HCHO reacting with LYS or EC, that is, M_LYS, M_EC‐6, and M_EC‐8, still have both nucleophilic and electrophilic sites, which are elements to form ternary cross‐linking in vegetable‐aldehyde–collagen system. The analysis of energy gap between HOMO (highest occupied molecular orbit) and LUMO (lowest unoccupied molecular orbit) indicate that the intermediate of HCHO–LYS residues (M_LYS) can further react with free HCHO to form product P‐N(CH₂OH)₂ (P‐N‐represents amino acid residue; N represents nitrogen atom on side chain), but the reaction of intermediate M_LYS with free EC is difficult to take place. So, the probability of forming ternary cross‐linking structure of amino acid residue–HCHO–EC is small, if HCHO is added before vegetable tannin in vegetable‐aldehyde–collagen system. However, the reactions of EC–HCHO intermediates (M_EC‐6 and M_EC‐8) with free amino acids, HCHO–amino acid residue intermediate (M_LYS), as well as with other EC–HCHO intermediates (M_EC‐6 and M_EC‐8), are very easy to take place. The reaction enthalpy also shows that the cross‐linking tendency is favorable in thermodynamics. So, it can be deduced that covalent cross‐linking among amino side chain of collagen and vegetable tannin may take place when aldehyde is added after vegetable tannin. In this way, a multiple point cross‐linking reaction occurs to create a high stabilization of collagen. © 2011 Wiley Periodicals, Inc.     

CoCl_2·6H_2O or LaCl_3·7H_2O Catalyzed Biginelli Reaction. One-Pot Synthesis of 3,4-Dihydropyrimidin-2(1 H)-ones

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磷钼酸：一种有效的催化三组分反应合成1-酰胺烷基-2-萘酚的Keggin型杂多酸

磷钼酸,一种环境友好的杂多酸催化剂,可以有效地催化2-萘酚、脲或酰胺和醛的三组分“一锅”反应生成1-酰胺烷基-2-萘酚。该方法得率高,操作简单。     

Bismuth triflate–L(−)‐proline catalyzed synthesis of chiral 2,5‐diaryl‐2,3‐dihydropyrano[2,3‐b]quinolin‐4‐ones

The synthesis of chiral (2R) 2,5‐diaryl‐2,3‐dihydropyrano[2,3‐b]quinolin‐4‐ones, was achieved, at ambient temperature, by the reaction of 3‐acetyl‐4‐aryl‐carbostyril and an aldehyde, in the presence of bismuth triflate–L(?)‐proline complex, formed in situ. The products were obtained in 62–78% yield with high enantioselectivity (72–96% ee). J. Heterocyclic Chem., (2011).     

A Novel and Efficient Catalyst to One‐Pot Synthesis of 2‐Amino‐4H‐Chromenes by Methanesulfonic Acid

Methanesulfonic acid efficiently catalyzes the one‐pot, three component reaction of an aromatic aldehyde, malonitrile and α or β‐naphthol to yield 2‐amino‐4H‐chromenes in very good yields.     

The Retro‐Hydroformylation Reaction

Hydroformylation, a reaction that adds carbon monoxide and dihydrogen across an unsaturated carbon–carbon multiple bond, has been widely employed in the chemical industry since its discovery in 1938. In contrast, the reverse reaction, retro‐hydroformylation, has seldom been studied. The retro‐hydroformylation reaction of an aldehyde into an alkene and synthesis gas (a mixture of carbon monoxide and dihydrogen) in the presence of a cyclopentadienyl iridium catalyst is now reported. Aliphatic aldehydes were converted into the corresponding alkenes in up to 91 % yield with concomitant release of carbon monoxide and dihydrogen. Mechanistic control experiments indicated that the reaction proceeds by retro‐hydroformylation and not by a sequential decarbonylation–dehydrogenation or dehydrogenation–decarbonylation process.     

New conditions for synthesis of (±)‐2‐monosubstituted and (±)‐2,2‐disubstituted 2,3‐dihydro‐4(1H)‐quinazolinones from 2‐nitro‐ and 2‐aminobenzamide

An efficient synthesis of (±)‐2‐monosubstituted and (±)‐2,2‐disubstituted 2,3‐dihydro‐4(1H)‐quinazolinones has been developed using a dissolving metal reduction‐condensative cyclization strategy. Treatment of 2‐nitrobenzamide and an aldehyde or ketone with iron powder in refluxing acetic acid affords high yields of the title compounds. More complex ring systems are available by incorporating additional reactive functionality γ to the carbonyl of the aldehyde or ketone substrate. The scope and limitations of the process along with optimized procedural details are presented. The same target molecules are also accessible by reaction of 2‐aminobenzamide with aldehydes and ketones in refluxing acetic acid. J. Heterocyclic Chem., (2011).     

Asymmetric Diels–Alder Reaction of α‐Substituted and β,β‐Disubstituted α,β‐Enals via Diarylprolinol Silyl Ether for the Construction of All‐Carbon Quaternary Stereocenters

The asymmetric Diels–Alder reaction of α‐substituted acrolein proceeds in the presence of the trifluoroacetic acid salt of trifluoromethyl‐substituted diarylprolinol silyl ether to afford the exo‐isomer with both excellent diastereoselectivity and high enantioselectivity. In the Diels–Alder reaction of a β,β‐disubstituted α,β‐unsaturated aldehyde, good exo‐selectivity and excellent enantioselectivity was obtained when the perchloric acid salt of the bulky triisopropyl silyl ether of trifluoromethyl substituted diarylprolinol was employed as an organocatalyst in the presence of water. In both cases, all‐carbon quaternary stereocenters are constructed enantioselectively.     

One‐Pot synthesis of a novel compound N‐hydroxydecahydroacridine under microwave irradiation

A novel reaction to synthesis a series new N‐hydroxyldecahydroacridine derivatives by a one‐pot condensation of aldehyde, 1,3‐dicarbonyl compound and NH₂OH in glycol under microwave irradiation is described. N‐hydroxyldecahydroacridine was obtained in excellent yields (81–95%) within short reaction time (4–7 min)