Enantioselective aza-Michael reaction of hydrazide to chalcones through the nonactivated amine moiety conjugated addition

The catalytic asymmetric aza-Michael reaction of benzoyl hydrazine toward chalcones through the nonactivated amine moiety conjugated addition was facilitated by the developed N,N'-dioxide-Sc(OTf)(3) complex under mild conditions, affording the pharmacologically and synthetically useful products in moderate to high yields with up to 97% ee.     

The synthesis of unsubstituted cyclic imides using hydroxylamine under microwave irradiation

Unsubstituted cyclic imides were synthesized from a series of cyclic anhydrides, hydroxylamine hydrochloride (NH2OH.HCl), and 4-N,N-dimethylamino-pyridine (DMAP, base catalyst) under microwave irradiation in monomode and multimode microwaves. This novel microwave synthesis produced high yields of the unsubstituted cyclic imides for both the monomode (61 - 81%) and multimode (84 - 97%) microwaves.     

Microwave assisted synthesis of novel methylenebis{2-[(1-benzyl/cyclohexyl-1H-1,2,3-triazol-4-yl)methoxy]chalcones} and their antibacterial activity

A series of novel methylenebis{2-[(1-benzyl/cyclohexyl-1H-1,2,3-triazol-4-yl)methoxy]chalcones} (IVa-IVn) have been synthesized by the Click reaction and Claisen-Schmidt condensation of 5,5′-methylenebis[2-(prop-2-yn-1-yloxy)benzaldehyde] under microwave irradiation with high yields. All products have been characterized by spectral data including FT-IR, ¹H, and ¹³C NMR, mass spectrometry, and tested for their antibacterial activity.     

KF‐Melamine Formaldehyde Resin (KF‐MFR) as a Versatile and Efficient Heterogeneous Reagent for Aldol Condensation of Aldehydes and Ketones under Microwave Irradiation

KF‐Melamine formaldehyde resin (KF‐MFR) was demonstrated to be a highly efficient heterogenious catalyst for cross‐aldol condensation under microwave irradiation. In this synthesis, various aldehydes and ketones were condensed together in the presence of supported KF on melamine‐formaldehyde resin to afford different chalcone derivatives in good to excellent yields. KF‐MFR proved to have unique termal and chemical resistance and can be reused for many consecutive runs without remarkable loss in catalytic activity.     

An Efficient Green Synthesis of a New Class of α‐Aminophosphonates under Microwave Irradiation Conditions in the Presence of PS/PTSA

The present work focuses on the study of catalytic activity of polystyrene‐supported p‐toluenesulfonic acid (PS/PTSA) and the synthesis of α‐aminophosphonates from the Kabachnik–Fields (KF) reaction under microwave irradiation in solvent‐free conditions. Recently, the catalytic activity of PS/PTSA was tested with good yields. This procedure is the simplest, most straightforward, environment friendly method for the synthesis of α‐aminophosphonates from simple to different substituted aldehyde substrates. Furthermore, this catalyst can be recovered and reused without loss of its catalytic activity.     

Microwave-Assisted Rapid Synthesis of Neurotransmitter Release Enhancer Linopiridine and Its New Analogues

Abstract

A neurotransmitter release enhancer linopiridine and its new analogues have been synthesized rapidly in yields from the 1:2 coupling of oxiindole with 4-picolyl chloride hydrochloride on the surface of basic alumina doped with 37% KF under microwave irradiation in solvent-free conditions.     

A FACILE SYNTHESIS OF CONJUGATED ACETYL KETONES BY Pd(II)-Cu(I) DOPED KF/Al2O3-CATALYZED UNDER MICROWAVE IRRADIATION

A rapid and efficient method for synthesis of α,β-conjugated acetylenic ketones involves reaction ofphenylacetylene with aroyl chlorides in the presence of acatalytic amount Pd(PPh₃)₂Cl₂-CuIdoped KF/Al₂O₃ under microwave irradiationto give the corresponding α,β-conjugated acetylenicketones 3a–g in 81–94% yield.     

A route to functionalized pyrimidines from carbohydrates via amine-driven dehydrative ring transformations

A novel and expeditious synthetic protocol for functionalized pyrimidines using unprotected aldoses as biorenewable resources is reported. The synthesis involves aza-Michael addition of aromatic amines to aldose-derived 1,3-oxazin-2-ones(thiones) followed by dehydrative ring transformation to afford 4-polyhydroxyalkylpyrimidin-2-ones(thiones) in excellent yields. This is a one-pot Montmorillonite K-10 clay-catalyzed amine-driven process proceeding under solvent-free microwave irradiation conditions.     

Efficient solvent-free synthesis of bis(indolyl)methanes on SiO<Subscript>2</Subscript> solid support under microwave irradiation

An efficient synthesis of bis(indolyl)methanes was developed. Bis(indolyl)methanes were synthesized starting from various aromatic aldehydes with indole under microwave irradiation and solvent-free conditions (85–98 %). Solid support SiO₂ was found to possess favorable catalytic and dispersancy parameters for the condensation reaction. Moreover, novel bis(indolyl)methanes containing an isoxazole ring were synthesized via this method in excellent yields (> 94 %) using 3-substituted isoxazole-5-carbaldehydes and indole.     

Enzyme-catalyzed asymmetric domino aza-Michael/aldol reaction for the synthesis of 1,2-dihydroquinolines using pepsin from porcine gastric mucosa

An unprecedented enzyme-catalyzed asymmetric domino aza-Michael/aldol reaction of 2-aminobenzaldehyde and a,b-unsaturated aldehydes is achieved. Pepsin from porcine gastric mucosa provided mild and efficient access to diverse substituted 1,2-dihydroquinolines in yields of 38%–97% with 6%–24%enantiomeric excess(ee). This work not only provides a novel method for the synthesis of dihydroquinoline derivatives, but also promotes the development of enzyme catalytic promiscuity.     

微波相转移催化氧化法合成氯代苯甲酸

在相转移催化剂存在下，用微波辐射快速合成氯代苯甲酸。考察了微波辐射功率、辐射时间、相转移催化剂对反应的影响。实验证明：在455W的微波辐射下，以季铵盐A-1为相转移催化剂，反应3min，对氯苯甲酸、邻氯苯甲酸的产率分别达72．5％和71．8％。     

Intramolecular cyclization of delta-iminoacetylenes: a new entry to pyrazino[1,2-a]indoles

[reaction: see text] The synthesis of the pyrazino[1,2-a]indole nucleus was achieved by intramolecular cyclization of several 2-carbonyl-1-propargylindoles in the presence of ammonia. The reaction conditions were optimized using microwave heating and a pool of catalysts. Cyclization of 1-alkynylindole-2-carbaldehydes was easily accomplished under standard heating conditions, whereas microwave heating contributed to reduced reaction times and improved overall yields. Moreover, a fine-tuning of the microwave irradiation time made possible the selective synthesis of both pyrazino[1,2-a]indole isomers. TiCl4 proved the catalytic system of choice to achieve pyrazinoindoles in satisfactory yields starting from 1-alkynyl-2-acetylindoles and 1-alkynyl-2-benzoylindole derivatives. Also in these cases, microwave heating contributed to faster reactions and improved yields. The uncatalyzed versus catalyzed reaction mechanism is discussed.     

2-取代-4(3H)-喹唑啉酮在Br(o)nsted酸性功能化离子液体中的微波合成

以N-甲基咪唑、吡啶为起始原料,合成了二种新型Br(o)nsted酸性功能化离子液体:1-(4-磺酸基)苄基-3-甲基咪唑硫酸氢根盐(3a),N-(4-磺酸基)苄基吡啶硫酸氢根盐(3b),以其作为反应介质与催化剂,研究了2-取代-4(3H)-喹唑啉酮的三组分、一锅法微波合成.结果表明,当n(2-氨基苯甲酸):n(酰氯):n(乙酸铵):n(3a或3b)=1:1.2:1.5:0.1时,反应6 min即可完成,产率81%～95%.离子液体经减压蒸馏、真空干燥可重复使用3次,催化活性基本保持不变.     

An efficient and reusable heterogeneous catalyst Animal Bone Meal for facile synthesis of benzimidazoles, benzoxazoles, and benzothiazoles

A library of benzimidazoles, benzoxazoles, and benzothiazoles was efficiently synthesized by condensation of o-phenylenediamine, o-aminophenol, and o-aminothiophenol respectively with aromatic aldehydes in the presence of catalytic amounts of Animal Bone Meal (ABM) and Lewis acids doped ABMs. Reactions were conducted under reflux conditions in air. The remarkable features of this new protocol are high conversion, short reaction times, and cleaner reaction profiles, straightforward procedure, and reduction in catalyst toxicity.     

Efficient microwave access to polysubstituted amidines from imidoylbenzotriazoles

Microwave reactions of primary and secondary amines with imidoylbenzotriazoles 6a-w gave diversely substituted amidines 7a-Aa in 76-94% yields. Convenient preparations of a variety of amides 5a-Ab (87-96%) and imidoylbenzotriazoles 6a-w (56-95%) have also been developed using microwave irradiation under mild conditions and short reaction times. These results demonstrate further the advantages of microwave synthesis and introduce a new application of imidoylbenzotriazoles in the preparation of polysubstituted amidines.     

Pd-catalysed conjugate addition of arylboronic acids to <Emphasis Type="Italic">α,β</Emphasis>-unsaturated ketones under microwave irradiation

The Pd-catalysed conjugate addition of arylboronic acids to α,β-unsaturated cyclic ketones was studied under controlled microwave irradiation conditions. A variety of catalysts, bases and solvents was explored in order to achieve optimum yields in the shortest possible reaction time. Under optimised conditions (Pd(OAc)₂/2,2′-bipyridine and KF in a mixture of toluene, water, and acetic acid and 10 min microwave irradiation), a range of arylboronic acids was successfully added to several cyclic enones. With chiral phosphane ligands, a promising enantioselectivity was obtained (85 % ee).     

Microwave-assisted arylation of rac-(E)-3-acetoxy-1,3-diphenylprop-1-ene with arylboronic acids

The palladium-catalyzed arylation of rac-(E)-3-acetoxy-1,3-diphenylprop-1-ene with arylboronic acids was studied under controlled microwave irradiation conditions. A variety of different catalysts, bases, and solvents were explored in order to achieve optimum yields in the shortest possible reaction times. The best isolated yields were obtained using Pd₂(dba)₃·CHCl₃/PPh₃ as the catalytic system, potassium phosphate monohydrate as the base, and toluene/H₂O as a solvent system. Microwave irradiation using 5 mol % of the palladium catalyst for 90 s (max. temp 170 °C) generally afforded the cross-coupling products in good to excellent yields.     

Microwave-promoted efficient conversion of acetophenones to 1,3,5-triarylbenzenes catalyzed by H3PW12O40 and nano-silica supported H3PW12O40 as reusable catalysts

H₃PW₁₂O₄₀ and nano-silica supported H₃PW₁₂O₄₀ were found to be efficient heterogeneous catalysts for the preparation of 1,3,5-triarylbenzenes via triple self condensation of acetophenones under microwave irradiation and solvent-free conditions. High yields, short reaction times, easy work-up, easy availability and handling, eco-friendly and reusability of the catalysts are the main aspects of the present method. The catalytic mechanism of 1,3,5-triarylbenzenes synthesis is also proposed.     

An efficient conjugate hydrocyanation of chalcones and related enones with TMSCN under solvent- and additive-free microwave conditions

A first example of solvent- and additive-free 1,4-addition reaction of α,β-unsaturated ketones such as chalcones, 3-nonen-2-one and benzalacetone with trimethylsilyl cyanide (TMSCN) is described. The addition of TMSCN to chalcones, 3-nonen-2-one, and benzalacetone under microwave irradiation in the absence of Lewis or Brønsted acids and solvents, yielded the corresponding β-cyanoketones in good to moderate yields, as quite rapidly as in 5 min. No systematic substituent effect of chalcones on the yields was observed. No reaction of α,β-unsaturated esters such as methyl cinnamate with TMSCN took place under the same conditions.     

MICROWAVE-ASSISTED COUPLING REACTION BY COPPER(I)-CATALYZED OF TERMINAL ALKYNES WITH AROYL CHLORIDES

A rapid and efficient method for synthesis of α, β-conjugated acetylenic ketones involves reaction of phenylacetylene with aroyl chlorides in the presence of catalytic amount CuI under microwave irradiation to give the corresponding α, β-conjugated acetylenic ketones 3 a–i in 76–93% yields.