Highly Efficient Solvent-Free Synthesis of Dihydropyrimidinones Catalyzed by Zinc Oxide

A simple, efficient and practical procedure for the Biginelli reaction using zinc oxid (ZnO) as a novel and reusable catalyst is described under solvent-free conditions in high yields. The use of this agent is characterized by remarkable reactivity, moderate costs, low toxicity and simple work up procedures.     

An Efficient Method for Production and Storage of Unstable S-Nitrosothiols Under Mild and Heterogeneous Condition with Sodium Nitrite and Oxalic Acid Dihydrate

Thiols can be readily converted to their corresponding nitrosothiols with a combination of oxalic acid and sodium nitrite in t-butanol at room temperature (26-30°C). The reaction mixture could be solidified with decreasing its temperature to, 15°C and was stored for several days without any destruction of the nitrosothiols.     

Novel Approach for the Synthesis of N-Substituted-4-(2-methyl-4-oxo-4H-quinazolin-3-yl)-butyramides

A simple and convenient method for the synthesis of N-substituted-4-(2-methyl-4-oxo-4H-quinazolin-3-yl)-butyramides has been reported. Several aromatic and aliphatic amide derivatives of 4-(2-methyl-4-oxo-4H-quinazolin-3-yl)-butyric acid were prepared in 60–81% yields by refluxing it with different phosphazo compounds in toluene for approximately 1 h.     

KG-60-Piperazine as a New Heterogeneous Catalyst for Gewald Three-Component Reaction

Piperazine supported on amorphous silica (KG-60-piperazine) as a basic catalyst acts in the Gewald three-component reaction of some aldehydes and ketones with malononitrile as well as ethyl cyanoacetate. The catalyst shows general utility with a variety of starting carbonyl compounds. Moreover, the catalyst can be reused for four additional cycles without significant loss of the activity.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Trifluoroacetic Acid as an Efficient Catalyst for One-Pot,Four-Component Synthesis of 1,2,4,5-Tetrasubstituted Imidazoles Under Microwave-Assisted,Solvent-Free Conditions

An efficient method for synthesis of various tetrasubstituted imidazoles, using trifluoroacetic acid (TFA) as a catalytic support, by four-component condensation of benzil, aldehydes, amines, and ammonium acetate under microwave-irradiated, solvent-free conditions is described.     

Microwave Assisted Synthesis of Dibenzoxazepines

Dibenzo[b,f][1,4]oxazepine derivatives were synthesized in good yields and short reaction times by the reaction of 2‐chlorobenzaldehydes and 2‐aminophenoles in basic conditions under microwave irradiation.     

Silica Chromate as a Novel Oxidizing Agent for the Oxidation of 1,4‐Dihydropyridines

Silica chromate easily converts 1,4‐dihydropyridines to their corresponding pyridines in the presence of NaHSO₄ · H₂O and wet SiO₂ in dichloromethane at room temperature in good to excellent yields.     

Convenient Synthesis of 2-Aminothiophene Derivatives by Acceleration of Gewald Reaction Under Ultrasonic Aqueous Conditions

Under ultrasound irradiation and in the presence of H₂O/Et₂NH, ethyl cyanoacetate or malononitrile can combine with α-methylene carbonyl compounds and elemental sulfur to efficiently yield 2-aminothiophene derivatives within a few minutes. Products are easily obtained by simple filtration because of their spontaneous precipitation in the reaction mixtures.     

Solvent-Free C-Benzoylation and N-Benzoylation Reactions Using Microwave Heating

An ecofriendly and efficient microwave-irradiated solvent-free benzoylation method was developed. The procedure for C-benzoylation used 50 mol% AlCl₃ as a Lewis acid catalyst at 130 °C and was completed in 10 min. The isolated yield was between 71% and 100%. N-benzoylation was conducted in a catalyst-free environment at 130 °C in 10 min. The isolated yield was between 80% and 100%.