Microwave-Assisted Michael Addition of Diethyl Malonate with Ferrocenyl Substituted Chalcones Under Solvent-Free Conditions

The article describes an efficient, economical, and environmentally friendly approach for Michael addition of diethyl malonate to ferrocenyl substituted chalcones in the presence of microwave irradiation under solvent-free conditions, affording the corresponding Michael adducts in moderate to good yields of 53–94%.

A New and Efficient Procedure for the Production of 1,1-Diacetate from Corresponding Aldehydes Promoted by Silica Chromate (SiO2-O-CrO2-O-SiO2)

Abstract

A wide range of aromatic aldehydes has been selectively converted to 1,1-diacetates using silica chromate (SiO₂?O?CrO₂?O?SiO₂) under solvent-free conditions at room temperature in moderate to good yields. This protocol is mild and efficient compared to other reported methods.

GRAPHICAL ABSTRACT     

Chemoselective Deprotection of Thioacetals/Thioketals Using HIO3 in the Presence of Wet SiO2 Under Mild Solvent-Free Conditions

Abstract

HIO ₃ in the presence of wet SiO ₂ is highly efficient and a mild reagent for selective deprotection of a variety of thioacetals/thioketals to the corresponding parent carbonyl compounds at room temperature and under solvent-free conditions.     

Chemoselective Protection of Carbonyl Compounds as Dithioacetals Using Silica Gel Supported Aluminium Chloride

Abstract

Silica gel supported aluminium chloride is shown to be a mild chemoselective catalyst for dithioacetalization of carbonyl compounds.     

Efficient Method for Thioacetalization of Carbonyl Compounds in the Presence of a Catalytic Amount of Benzyltriphenylphosphonium Tribromide (BTPTB) under Solvent-Free Conditions

A variety of carbonyl compounds have been successfully converted to the corresponding thioacetal derivatives in good to excellent yields on reaction of carbonyl compounds with 1,2-ethanedithiole, 1,3-propanedithiol, and ethylthiol in the presence of a catalytic amount of benzyltriphenylphosphonium tribromide (BTPTB) under solvent-free conditions. Some of the major advantages of this method are mild reaction conditions, high efficiency, and the compatibility with other reported methods. In addition, no bromination occurs at the double bond or α to the keto position or even in the aromatic ring under these experimental conditions.     

硅胶催化的微波加热无溶剂制备芳香酰胺实验设计

通过微波加热实现无溶剂制备N-苯基苯甲酰胺是典型的绿色酰胺化方法。这一方法采用廉价、环保的柱色谱硅胶为催化剂,催化性能好,效率高。使用苯甲酸和苯胺在120 ℃条件下10 min内完成酰化反应,产率大于90%,这一反应不仅原子经济,而且节约能源,因此,这一实验完全适合于大学实验教学中作为绿色有机实验推广使用。     

Synthesis of 1,5-Benzodiazepines with Unusual Substitution Pattern from Chalcones Under Solvent-Free Microwave Irradiation Conditions

1,5-Benzodiazepines have been synthesized from the corresponding 2′-hydroxychalcones [1-(2-hydroxyphenyl)-3-aryl-2-propen-1-ones] and o-phenylenediamine, both in methanol, under reflux and under solvent-free microwave irradiation conditions on alumina. The latter method proved to be advantageous.     

硅胶硫酸催化肟转化为羰基化合物的有效方法

在硅胶硫酸催化和十二烷基磺酸钠存在下,肟与多聚甲醛在90℃的水溶液中搅拌反应15～120 min生成相应的羰基化合物,收率68%～98%.     

Regeneration of Carbonyl Compounds from Phenylhydrazones Under Microwave Irradiation

An environmentally benign, efficient, and mild methodology for the cleavage of phenylhydrazones using potassium ferrate under microwave irradiation in solvent-free conditions is described.     

Regeneration of Carbonyl Compounds from Oximes and Hydrazones Using Peroxymonosulfate on Silica gel under Solvent-free Conditions

In an environmentally benign solvent-free system, oximes and hydrazones are rapidly transformed into parent carbonyl compounds using peroxymonosulfate on silica gel under microwave irradiation in good to excellent yields.     

Highly Selective Regeneration of Carbonyl Compounds from Their Oximes and Semicarbazones in Aqueous Medium

Abstract

Chemoselective regeneration of aryl alkyl ketone, α‐tetralone, and cycloalkanone by hydrolysis of their oximes and semicarbazones has been accomplished using aqueous phosphoric acid without involvement of any organic cosolvent in the reaction medium, where the similar derivatives of aryl aldehyde, diaryl ketone, aliphatic acyclic aldehyde and ketone remain mostly inert.     

A New Bismuth Nitrate–Catalyzed Electrophilic Substitution of Indoles with Carbonyl Compounds Under Solvent-Free Conditions

An expeditious synthetic method for the preparation of bis(indollyl)methane derivatives has been developed through a bismuth nitrate-catalyzed reaction of indole with various carbonyl compounds in mortar and pastle under solvent-free conditions.     

Efficient and Green Microwave-Assisted Multicomponent Biginelli Reaction for the Synthesis of Dihydropyrimidinones Catalyzed by Heteropolyanion-Based Ionic Liquids Under Solvent-Free Conditions

An efficient and green route for the synthesis of dihydropyrimidinones via microwave-assisted Biginelli reaction catalyzed by 3 mol% of heteropolyanion-based ionic liquids under solvent-free conditions has been reported. The practical reaction was found to be compatible with different structurally diverse substrates. Good to excellent yields, short reaction times, and operational simplicity are the main highlights of this protocol. Moreover, the heteropolyanion-based ionic liquids were easily reusable for this Biginelli reaction.     

Synthesis of Biscoumarins from 4-Hydroxycoumarin and Aromatic Aldehydes—A Comparative Assessment of Percentage Yield Under Thermal and Microwave-Assisted Conditions

A convenient synthesis of various biscoumarins by condensing a series of aldehydes with 4-hydroxycoumarin under microwave irradiation is reported for the first time along with a comparative account of the syntheses under conventional conditions. The reaction times have been reduced considerably with improvement in yields in comparison to thermal conditions. The reactions have been carried out in solvent as well as under solvent-free conditions, and the adopted procedure provides an energy-and time-saving protocol.     

Microwave-Assisted,Rapid, Solvent-Free Aza-Michael Reaction by Perchloric Acid Impregnated on Silica Gel

Highly efficient solvent-free aza-Michael additions of a variety of amines to α,β-unsaturated carbonyl compounds under microwave-irradiation conditions catalyzed by perchloric acid impregnated on silica gel (HClO₄/SiO₂) is reported. The reactions are completed within 2–7 min in a microwave oven to produce the corresponding adducts in excellent yields, and the catalyst can be recovered and reused.     

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.     

Facile Method for One-Step Synthesis of 2,4,5-Triarylimidazoles Under Catalyst-Free,Solvent-Free,and Microwave-Irradiation Conditions

A green and efficient method for the synthesis of 2,4,5-triarylimidazoles by one-step condensation reaction of benzil, aromatic aldehyde, and ammonium acetate under catalyst-free, solvent-free, and microwave-irradiation conditions is reported. This method had many dramatic advantages, such as the short reaction time (3–5 min), good yields (80–99%), environmental friendliness, and convenient operation.     

A New Protocol for O-Methylation of Phenolic Compounds with Trimethyl Phosphite or Trimethyl Phosphate Under Solvent-Free Condition and Microwave Irradiation

A simple method for the preparation of industrially important alkyl aryl ethers is reported. Several phenolic compounds such as phenols, naphthols, and hydroxy coumarins were O-methylated with trimethyl phosphite or trimethyl phosphate under microwave irradiation and solvent-free condition in almost quantitative yields. Reaction of 2-naphthol with trimethyl phosphate gave mixture of 2-methoxynaphthalene and 1-methyl-2-methoxynaphthalene while the reaction with trimethyl phosphite gave mostly 2-methoxynaphthalene. This method is highly efficient for the methylating of phenolic compounds with very easy experimental procedure and environmental friendly conditions.