Efficient synthesis of β-enaminones and β-enaminoesters catalyzed by gold (I)/silver (I) under solvent-free conditions

An efficient method for the synthesis of β-enaminones and β-enaminoesters using a combination of [(PPh(3))AuCl]/AgOTf as catalyst has been developed. The reaction between 1,3-dicarbonyl compounds and primary amines was carried out under solvent-free conditions with low catalyst loading in good to excellent yields at room temperature.     

A simple protocol for the preparation of β-enamino ketones catalyzed by NbOPO4 under solvent free conditions

A novel application of the highly stable niobium oxide phosphate (NbOPO₄) as an efficient catalyst for the synthesis of β-enamino ketones under solvent-free conditions is described. This protocol, exhibits attractive yields, short reaction periods, lower loading of catalyst and high chemoselectivity.     

PMA-SiO2 catalyzed synthesis of β-keto enol ethers

An efficient conversion of β-diketones into correspondingβ-keto enol ethers with catalytic amount of PMA-SiO_2 has been achieved.     

A facile synthesis of α-aminophosphonates catalyzed by ytterbium perfluorooctanoate under solvent-free conditions

Three-component reactions of aldehydes, amines and diethyl phosphite are efficiently catalyzed by ytterbium perfluorooctanoate [Yb(PFO)₃] under solvent-free conditions, giving the corresponding α-aminophosphonates in good to excellent yields. The catalyst can be recovered and reused for several times without any significant loss of activity. Furthermore, a possible mechanism for this transformation is also presented.     

One-pot three-component reaction; synthesis of new symmetrically bridge 4,4′-(1,4-phenylene)di-pyrimidines under solvent free conditions

The present article describes a facile one-pot synthesis of a new series of 4,4′-(1,4-phenylene)-dipyrimidines ( 6a–c and 10a, b ) by the reaction of terephthalaldehyde ( 1 ), 2-acetylthiophene, and/or nitriles with S-benzylthiouronium chloride 3a . And also, the di-pyrimidinones 13a-d were obtained by the reaction of different amidines 3a–d and ethyl cyanoacetate ( 11 ) with terephthalaldehyde ( 1 ) under solvent-free conditions in the existence of sodium hydroxide which is found to be a more efficient base for these reactions. The final products were characterized by spectral data and elemental analysis, IR, MS, ¹ H, and ¹³ C NMR spectroscopy.     

Michael addition of indoles to β-nitrostyrenes catalyzed by HY zeolite under solvent-free conditions

Michael addition of indoles to β-nitrostyrenes is reported using HY zeolite as catalyst under mild reaction conditions. This methodology allows the synthesis of various indole derivatives in good to high yields at 50 °C under solvent-free conditions. The short reaction time and achieving high yield of the desired products are the main advantages of the present work. The catalyst can be easily recovered and reused for six successive runs without considerable changes in yields. This Michael addition catalyzed by HY zeolite is operationally simple and can be considered as a greener protocol as it avoids the use of corrosive acids and toxic reagents.     

Catalyst-free direct synthesis of β-enaminones through reaction of benzohydrazonamides with cyclic 1,3-diketones: Access to exocyclic β-enaminones

Abstract

The reaction of benzohydrazonamides with cyclic 1,3-diketones affords β-enaminones in good to excellent yields (14 examples, 69???89%). This transformation proceeds under mild reaction conditions (ethyl acetate, 25?°C, 12???24?h) in the absence of any catalyst and gives access to novel nitrogen-rich organic scaffolds.     

Nano ceria catalyzed synthesis of α-aminophosphonates under ultrasonication

A simple, efficient and general method has been developed for the one-pot three component syntheses of α-aminophosphonates. The condensation of aldehyde, amine and triethyl phosphite by employing CeO₂ nanoparticles as catalyst gave α-aminophosphonates. The catalyst showed good recyclability. Nano CeO₂ has been found to be an excellent catalyst for the green synthesis of α-aminophosphonates under ultrasound irradiation and solvent-free condition. The α-aminophosphonates are obtained in good to excellent yield. This catalyst provides cleaner conversion, short reaction time and high selectivity which makes the protocol feasible and economical attractive.     

Iodine catalyzed efficient synthesis of symmetrical diaryl sulfoxides from arenes and thionyl chloride under solvent-free conditions

Synthesis of symmetrical diaryl sulfoxides from arenes and thionyl chloride in the presence of a catalytic amount of iodine at room temperature under solvent-free conditions is described.Mild reaction conditions,easy workup,high yield,and easily available catalyst are important features of this method.     

Highly efficient synthesis of β-amino esters via Mannich-type reaction under solvent-free conditions using ZnCl_2 catalyst

β-Amino esters were synthesized via ZnCl_2-catalyzed Mannich-type reaction of imines and malonate esters under solvent-free conditions in 6 min.Theβ-amino ester was converted into the corresponding aspartic acid derivatives.     

Ytterbium triflate catalyzed synthesis of β-functionalized indole derivatives

Ytterbium triflate was shown to be effective in promoting the synthesis of substituted indole derivatives starting from indole, aldehydes, and dimethyl malonate by a Yonemitsu-type three component reaction. The whole process was carried out in solvent-free conditions and furnished the desired adducts in 42-67% yield.     

β-Cyclodextrin-assisted synthesis of Biginelli adducts under solvent-free conditions

A simple, green and efficient protocol was developed using β-cyclodextrin as a solid catalyst for the solvent-free synthesis of various Biginelli adducts. The advantages of our protocol included the following: (i) a metal-free methodology; (ii) high yields; (iii) simple and efficient work-up procedures; (iv) improved results under solvent-free conditions. β-cyclodextrin-catalyzed the Biginelli reactions for various aldehydes, demonstrating that it is an efficient and eco-friendly catalyst for the preparation of heterocyclic compounds.     

Sulfuric acid catalyzed addition of β-dicarbonyl compounds to alcohols under conventional heating and microwave-assisted conditions

The highly efficient direct addition of β-dicarbonyl compounds to secondary alcohols has been achieved using one of the cheapest acids, H₂SO₄, as the catalyst. For a series of β-dicarbonyl compounds and various secondary alcohols, the addition reactions all complete in 5 min with high yields both under the conventional heating condition and under the microwave heating condition. The comparison of the results obtained from the microwave heating condition with those obtained from the conventional heating condition shows that no obvious specific or nonthermal microwave effects exist in the microwave-assisted addition reactions.     

Protecting group free, stereocontrolled synthesis of β-halo-enamides

Enamides, dienamides, and enynamides are important building blocks in synthetic, biological, and medicinal chemistry as well as materials science. Despite the extensive breath of their potential utility in synthetic chemistry, there is a lack of simple, high-yielding methods to deliver them efficiently and as single isomers. In this paper, we present a novel, protecting group free, efficient, and stereoselective approach to the generation of β-halo-enamides. The methodology presented provides a robust synthetic platform from which E- or Z-enamides can be generated in good yields and with complete stereocontrol.     

Iridium catalyzed alkylation of 2′-hydroxyacetophenone with alcohols under thermal or microwave conditions

2′-Hydroxyacetophenone was alkylated with a range of substituted benzyl and heteroaryl alcohols to afford the corresponding C-alkylated products in good yields under microwave irradiation. The C-alkylated products were reacted with bromoacetonitrile to afford 2-amino-3-benzyl 1,4-naphthoquinone derivatives in moderate yields.     

Metal-free,PTSA catalyzed facile synthesis of β-ketoacetal from β-chlorocinnamaldehyde

A toluene solution of β-chlorocinnamaldehyde and dihydroxy alcohols in the catalytic presence of para-toluenesulphonic acid (PTSA) yield the β-ketoacetal in good to outstanding amount. The catalyst (PTSA), first selectively protect the aldehydic group to form the β-chloroacetal and the subsequent dechlorination by H₂O result the β-ketoacetal. Significant transformation was achieved with electron donating substituent attached at the para-position of cinnamaldehyde. The selective formation of β-keto-1,3-acetal was also obtained with a mixture of 1, 2- and 1, 3- diol. The present reaction consists of a metal-free, economical, robustly feasible, sizeable functional group tolerance and high yield properties. Moreover, the use of different dihydroxy alcohols made this process more benign and valuable towards the metal-free development of ketones. First, of its kind, a rare and unusual multitasking nature of PTSA is observed.     

Iron-catalyzed aminolysis of β-carbonyl 1,3-dithianes: synthesis of stereodefined β-enaminones and 3,4-disubstituted pyrazoles

A novel iron-catalyzed aminolysis of β-carbonyl 1,3-dithianes with various amines including ammonia, primary and secondary amines, as well as hydrazine hydrate has been developed, leading to the synthesis of stereodefined β-enaminones and 3,4-disubstituted pyrazoles in good to high yields.     

Visible-light photoredox-mediated oxidation of N-methyl tertiaryamines under catalyst free conditions:Direct synthesis of methylene-bridged bis-1,3-dicarbonyl compounds

Mediated by visible light-induced photoredox catalysis and free of other catalysts, a new and efficient synthesis of methylene-bridged bis-l,3-dicarbonyl derivatives has been developed. A variety of N-methyl tertiaryamines and 1,3-dicarbonyl compounds were investigated in this reaction.     

Mandelic acid catalyzed one-pot three-component synthesis of α-aminonitriles and α-aminophosphonates under solvent-free conditions at room temperature

Abstract

A simple, mild, straightforward, efficient and eco-friendly protocol has been developed for the synthesis of a series of α-aminonitriles via the one-pot three-component Strecker reactions between various aldehydes, amines and trimethylsilyl cyanide using a catalytic amount of mandelic acid as a naturally occurring, low-cost, efficient organo-catalyst under solvent-free conditions at room temperature. Under the same optimized conditions synthesis of α-aminophosphonates were also achieved via the one-pot three-component Kabachnik-Fields reactions of aldehydes, amines and triethyl phosphate.