Abstract: Synthetic work related to penicillin has led to a considerable advance in the Chemistry of oxazoles and oxazolones. New general methods have been devised for constructing the ring, and much light has been thrown on the behaviour of functional groups attached to an oxazole nucleus. Most of the oxazolones previously described were of the type II, obtainable by the Erlenmeyer Synthesis from acylglycines and aldehydes from the action of acetic anhydride on α-acylamino acids. The acetic anhydride method of preparing oxazolones has remained the most general procedure. The objective of the present investigation was to develop a method for fast synthesis of unsaturated azlactones using condensation between saturated azlactones and Schiff bases and their subsequent aminolysis by using green chemistry technique which led to better yield and remarkable reaction rate enhancement with optimum utilization of energy.

The present investigation is carried out with three sequential objectives:

(a) Preparation of Schiff Bases
(b) Synthesis of 4- Arylmethylene-2-phenyl-2-oxazolin-5-ones (i.e. Unsaturated azlactones) and
(c) Aminolysis of 4- Arylmethylene-2-phenyl-2-oxazolin-5-ones in presence of glacial acetic acid.

2-Phenyl-2-oxazolin-5-one (2), i.e. saturated azlactone was generated by cyclizing hippuric acid (1) with p-toluenesulphonyl chloride (Tosyl Chloride) in the presence of triethylamine base in dry benzene at room temperature which declines the risk of high pressure development associated with solution phase reaction.

The resultant intermediate (2) which is saturated azlactone, was condensed with different aromatic imines (3) under mild conditions and subsequent removal of solvent under reduced pressure to get the targeted product 4-arylmethylene-2-phenyl-2-oxazolin-5-ones (4), i.e. unsaturated azlactones in appreciable yields with sufficient purity. If refluxing is continued by adding little glacial acetic acid in the same flask for further 10 minutes, the anilinolysis of the 1,5-bond of 4-arylmethylene-2-phenyl-2-oxazolin-5-ones (4), i.e. unsaturated azlactones, yielded the product N-phenyl-2-benzoylamino-3-arylpropenamides (5). It is noteworthy that the reaction is completed within maximum of 30 minutes and all the steps can be carried out in one flask.

Keywords: Schiff bases, Saturated Azlactones, Unsaturated azlactones, Z-isomer, Azlactonization, Atom Economy Route

| DOI: 10.17148/IARJSET.2024.11603