One-pot access to 2-oxazolines via a Castro-Stephens coupling and intramolecular cyclization

Aim: Here, we have reported easy one-pot access to a series of oxazolines using a modified Castro-Stephens coupling protocol. Background: 2-oxazolines have been shown to have significant biological activity and wide-ranging applications in organic chemistry. These properties make oxazolines as heterocyclic compounds of immense importance. Objective: The objective of this study is to synthesize oxazoline derivatives via an economical and one-pot protocol. Method: 2-oxazoline has been synthesized through Cu-powder mediated Castro-Stephens coupling and intramolecular cyclization route. The mechanism involves a rearrangement in which one of the oxygen from the N-acylamino alcohol group is liberated as water and then transferred to alkyne functionality to form 2-oxazoline derivatives. The oxazolines were characterized by NMR, mass, and XRD studies. Result: The protocol is economically viable and uses readily available Cu-powder along with DMF for cross-coupling and cyclization steps.

Ultrasound-Accelerated, Concise, and Highly Efficient Synthesis of 2-Oxazoline Derivatives Using Heterogenous Calcium Ferrite Nanoparticles and Their DFT Studies

A rapid and operationally simple approach for synthesising biologically relevant 2-oxazoline derivatives has been developed through highly efficient ultrasound-promoted coupling reactions of thioamides and amino alcohols using calcium ferrite nanoparticles as heterogeneous catalysts. The major advantage of using ultrasound irradiation lies in the drastic reduction of reaction time as compared with conventional stirring. Furthermore, quantum chemical investigations for the synthesised 2-oxazoline derivatives have been carried out at the DFT/B3LYP/6-311 + G (d, p) level of theory to predict the optimized geometry. The molecular properties such as bond lengths, bond orders, Milliken charges, frontier molecular orbitals, global reactivity descriptors, molecular electrostatic potential map, and thermodynamic parameters of all the compounds have also been reported at the same level of theory.

Improved Synthetic Method for 5-[(Phenylthio)methyl]oxazoline Derivatives: Electrophilic Cyclization of Allylic Amide Using a Brønsted Acid and Tetrabutylammonium Chloride under Mild Conditions

The synthesis of oxazolines using electrophilic cyclization of allylic amide is a simple and powerful method. However, cyclization involving arylsulfenylation requires harsh reaction conditions. We found that the reaction proceeds under mild heating conditions with the combination of a Brønsted acid and tetrabutylammonium chloride. This method enabled the synthesis of 5-[(arylsulfenyl)methyl]oxazoline derivatives under mild conditions and demonstrated high tolerance for various functional groups.

A catalytic highly enantioselective allene approach to oxazolines

A completely different approach for the asymmetric construction of oxazoline derivatives with an excellent enantioselectivity via the palladium-catalyzed coupling-cyclization of N-(buta-2,3-dienyl)amides with aryl iodides has been reported.

Synthesis and characterization of two new chiral Kemp’s acid derivatives: structures fixed by a peculiar system of N–H···O, C–H···O and C–H···N hydrogen bonds

New chiral imide-oxazoline derivatives of Kemp’s acid were synthesized with the aim to produce new ligands suitable for catalytic asymmetric reactions. Compound