Catalytic Performance of Immobilized Sulfuric Acid on Silica Gel for N-Formylation of Amines with Triethyl Orthoformate

Direct additive-free N-formylation and N-acylation of anilines and synthesis of urea derivatives using green, efficient, and reusable deep eutectic solvent ([ChCl][ZnCl2]2)

In the current report, we introduce a simple, mild efficient and green protocol for N-formylation and N-acetylation of anilines using formamide, formic acid, and acetic acid as inexpensive, nontoxic, and easily available starting materials just with heating along stirring in [ChCl][ZnCl2]2 as a durable, reusable deep eutectic solvent (DES), which acts as a dual catalyst and solvent system to produce a wide range of formanilides and acetanilides. Also, a variety of unsymmetrical urea derivatives were synthesized by the reaction of phenyl isocyanate with a range of amine compounds using this benign DES in high to excellent yields. [ChCl][ZnCl2]2 showed good recycling and reusability up to four runs without considerable loss of its catalytic activity.

Mechanochemically-Assisted Passerini Reactions: A Practical and Convenient Method for the Synthesis of Novel α-Acyloxycarboxamide Derivatives

A carboxylic acid, an aldehyde, and an isonitrile were combined in a single step (Passerini reaction) under mechanochemical activation to produce several α-acyloxycarboxamide derivatives in high to excellent yields within 15 min of milling. Mechanochemistry, when combined with the diversity provided by multicomponent reactions, enables the efficient synthesis of the target compounds, with great atom economy, shorter reaction times, and experimental simplicity. The method allows for the rapid production of a vast library of complex compounds from a limited number of substrates.

N-Formamide as a carbonyl precursor in the catalytic synthesis of Passerini adducts under aqua and mechanochemical conditions

A new simple, efficient, and environmentally friendly protocol is presented for the catalytic synthesis of α-acyloxycarboxamides using N-formamides as a carbonyl precursor under aqua and mechanochemical conditions. Immobilized sulfuric acid on silica gel was employed for the synthesis of desired products, via the reaction of benzoic acid, 1-napthylisocyanide and various heterocyclic N-formamides. After a careful optimization of the reaction conditions, the desired Passerini products were obtained in high to excellent yields in short reaction times (10-30 min) at room temperature. The highly efficient and environmentally friendly method provides a facile access to a library of α-acyloxycarboxamides derivatives for future research on bioactivity screening.

Immobilized Sulfuric Acid on Silica Gel as Highly Efficient and Heterogeneous Catalyst for the One-Pot Synthesis of Novel α-Acyloxycarboxamides in Aqueous Media

The application of immobilized sulfuric acid on silica gel (H2SO4-SiO2) as an efficient and easily reusable solid catalyst was explored in the synthesis of novel α-acyloxycarboxamide derivatives via a Passerini reaction of benzoic acid, aldehyde/ketone, and isocyanides. The Passerini adducts were obtained in high to excellent yields within 10 min in aqueous media under catalytic conditions. The key advantages of the process include a short reaction time, high yields, the catalyst’s low cost, and the catalyst’s reusability.