Synthesis Of2-Oxazolines Using DAST Via Beckmann Rearrangement

In the recent few decades, discovery of the DAST mediated reaction system for organic reactions to form oxazolines has effected drastic and far-reaching changes in the scientific domain. This invention has engrossed the interest of chemists and is increasing our understanding of how a range of organic synthetic processes are enhanced.-its alluring tendency has been marked by numerous applications such as gasoline (petrol and diesel) and lube oil additives, pharmaceutical industries, surface-active agent, corrosion resistant coating, anti-foaming agents, textile chemicals, adhesives and binders, stabilizers for chlorinated hydrocarbons; thus justifying the rigorous research on the oxazoline compound. Today, extraordinary transformations to various natural products and biologically active molecules have been achieved where various oxazolines are useful as intermediates.Oxazoline intermediates entertain a great diversity of reaction patterns that can stand numerous functional groups. Additionally, oxazoline synthetic protocols using DAST are economically captivating procedures as most procedures have been used as surrogate for the traditionally tedious, toxic and sometimes unreliably low product-yielding. In recent progresses, demonstrations from various researchers make free from ambiguity the contributions of the versatility of modern oxazoline synthesis in the development of pharmaceutical libraries, and also in the polymer, material and petroleum industries.In our special case, methodologies used with other systems are mentioned in passing as a justification as to why oxazolines are considered to be species with special powers.Encouraged by the virtues of this, we have conveniently developed a method for the synthesis of highly functionalized2-oxazolines in a one pot component reaction of Ketoximes using DAST via Beckmann rearrangement. Our choice for using DAST was intended for the development of simple, safe and efficient method for their synthesis of oxazolines.In this report we established a novel and efficient route for synthesis of2-oxazolines from Ketoxime substrate. This route involved a one-pot amidation of diketene with different amines at70℃in the presence of toluene to form corresponding amides followed by reacting the amides with K2CO3and DMF at room temperature to form corresponding carboxamides and carboxylates. The carboxamides and carboxylates were then reacted with NH2OH.HCL and NaOAc in presence of ethanol and water to form Ketoximes which were subsequently reacted in one pot uni-molecular synthesis with DAST and dichloromethane at room temperature to form corresponding2-oxazolines via Beckmann rearrangement.With the above pathway a simple one-pot unimolecular component reaction approach for the synthesis of highly functionalized2-oxazolines in excellent yields from corresponding Ketoximes was developed. Our utility of DAST as the reagent via Beckmann rearrangement proved to be another extraordinary transformation of Ketoximes to various oxazoline derivatives. Added to its excellent conversions, the superiority of the Ketoxime is culminated by its ready availability. The reaction was not only achieved in a short time but also under favorable conditions like room temperature.