Chemoselective Synthesis of 1,1-Diacetates from Aldehydes Using Anhydrous Cobalt(II) Bromide Under Solvent-Free Conditions

A mild and efficient method has been developed for the chemoselective preparation of 1,1-diacetates (acylals) from aldehydes catalyzed in the presence of a catalytic amount (0.1 mmol) of anhydrous cobalt(II) bromide under solvent-free conditions. The remarkable selectivity under mild and neutral conditions, excellent yields, short reaction time, and easily available and inexpensive catalyst are important features of this method.     

NbCl5 as an Efficient Catalyst for the Synthesis of 1,5-Benzodiazepine Derivatives

1,5-Benzodiazepine derivatives were synthesized in moderate to excellent isolated yields by the condensation reactions of o-phenylenediamine and ketones catalyzed by NbCl₅ under mild conditions using n-hexane as solvent at 50°C. This method is simple and effective with good yields.     

Cupric Sulfate Pentahydrate: A Mild and Efficient Catalyst for the Chemoselective Synthesis of 1,1-Diacetates from Aldehydes in a Solvent-Free System

Summary. Cupric sulfate pentahydrate was found to be an efficient catalyst for the protection of aldehydes as 1,1-diacetates in high yields in a solvent-free system at room temperature. Ketones are not affected under these reaction conditions.     

Al(OTf)3 as an Efficient Catalyst for One-Pot Synthesis of Primary Diethyl 1-Aminophosphonates Under Solvent-Free Conditions

A simple and general method has been developed for the one-pot, three-component synthesis of a variety of primary 1-aminophosphonates catalyzed by Al(OTf)₃ under solvent-free conditions in good to high yields.     

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     

Nano-TiO2: An Efficient and Reusable Heterogeneous Catalyst for Ring Opening of Epoxides Under Solvent-Free Conditions

Nano-TiO₂ is an effective heterogeneous catalyst for the ring opening of epoxides with aromatic amines to afford β-amino alcohols in good to excellent yields at room temperature under solvent-free conditions. It was found that the catalyst is recyclable, and the activity of the catalyst was not weakened markedly even after several reaction cycles. In addition, the catalytic activity of TiO₂ strongly depends on particle size or surface area.     

Highly Efficient Synthesis of Substituted Benzenes in the Presence of B(HSO4)3 as a New and Reusable Catalyst Under Solvent-Free Conditions

A highly efficient and simple procedure for the synthesis of substituted benzenes is described. A broad range of ketones (alkyl–aryl ketones and cyclic ketones) were condensed via a cyclotrimerization reaction in the presence of catalytic amounts of boron sulfonic acid [B(HSO₄)₃], a new, highly efficient, and reusable catalyst, under solvent-free conditions. All reactions completed in short times without formation of any by-products. The catalyst was recovered and reused successfully for 15 cycles of the reaction.

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

Efficient Synthesis of Ferrocenylcyclohexenone Under Solvent-Free Conditions

An efficient method for the synthesis of a series of ferrocenylcyclohexenones via tandem Michael–aldol reaction of ferrocenyl-substituted chalcones with dibenzyl ketone under solvent-free conditions is described. It was found that the factors including the electronic nature of chalcone, basicity of the base, reaction time, and temperature have effects on the formation of the ferrocenylcyclohexenones.     

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.     

Antimony Trioxide as an Efficient Lewis Acid Catalyst for the Synthesis of 5-Substituted 1H-Tetrazoles

Sb₂O₃ was found to be effective as a catalyst for a smooth (2 + 3) cycloaddition of sodium azide with nitriles to afford 5-substituted 1H-tetrazoles in good yields.     

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.     

Simple and Efficient Method for Acetylation of Alcohols,Phenols, Amines,and Thiols Using Anhydrous NiCl2 Under Solvent-Free Conditions

Solvent-free acetylation of alcohols, phenols, amines, and thiols with acetic anhydride (Ac₂O) in the presence of 0.1 mol% (13 mg) anhydrous NiCl₂, an inexpensive and easily available catalyst. Excellent yields, short reaction time, and mild reaction conditions are important features of this method.     

Simple and Efficient Method for Acetylation of Alcohols,Phenols, Amines,and Thiols Using Anhydrous NiCl2 Under Solvent-Free Conditions

Solvent-free acetylation of alcohols, phenols, amines, and thiols with acetic anhydride (Ac₂O) in the presence of 0.1 mol% (13 mg) anhydrous NiCl₂, an inexpensive and easily available catalyst, is described. Excellent yields, short reaction time, and mild reaction conditions are important features of this method.     

Simple Synthesis of Pyrroles Under Solvent-Free Conditions

Paal–Knorr condensation of 2,5-hexadione with primary amines in the presence of a catalytic amount of praseodymium(III) trifluoromethanesulfonate under solvent-free conditions has been accomplished with an excellent yield. This method is a very easy, rapid, and high-yielding reaction for the synthesis of N-substituted pyrrole derivatives.     

Sulfated Zirconia: An Efficient Catalyst for Solvent-Free Synthesis of Silyl Ethers Under Mild Conditions

Oximes, allylic, aliphatic, aromatic, cyclic, acyclic, and hetero alcohols are silylated in short reaction times with good yields in the midst of a catalytic amount of sulfated zirconia solid acid catalyst and trimethylsilyl cyanide under nonbasic, solvent-free, and ambient temperature conditions. Selectivity toward O-silyl ether rather than N-silyl ether has been observed. This simple experimental procedure, combined with easy recovery and reusability of the catalyst, is expected to contribute to the development of a clean and environmentally friendly strategy for the synthesis of O-silyl ethers.     

Highly Efficient Synthesis of Trioxopyrimidine-Based Chalconoids Under Solvent-Free Conditions

Straightforward procedures for the fast and efficient synthesis of differently substituted barbituric acid–based chalconoids under solvent-free conditions were developed.     

2,4,6-Trichloro-1,3,5-triazine as an Efficient Catalyst for Synthesis of Benzopyran Derivatives under Solvent-Free Conditions

An efficient and convenient procedure has been developed for the synthesis of benzopyran derivatives by one-pot condensation of substituted salicyaldehydes and substituted 1,3-hexanediones in the presence of a catalytic amount of 2,4,6-trichloro-1,3,5-triazine (TCT, cyanuric chloride) under solvent-free conditions.     

Synthesis of N-Substituted Pyrroles Under Catalyst- and Solvent-Free Conditions

N-Substituted pyrroles were synthesized under neat conditions by the reaction of aromatic amines with 2, 5-dimethoxytetrahydrofuran in excellent yields.