American Journal of Heterocyclic Chemistry 2019; 5(1): 1-3 http://www.sciencepublishinggroup.com/j/ajhc doi: 10.11648/j.ajhc.20190501.11 ISSN: 2575-7059 (Print); ISSN: 2575-5722 (Online) Study on the Condensation of Different Hydroxy Aromatic Aldehydes with 2-Substituted 2-Oxazolin-5-ones Generated in situ Pubanita Bhuyan, Pradeep K. Tripathy * Department of Chemistry, North Eastern Regional Institute of Science and Technology, Nirjuli, Itanagar, India Email address: * Corresponding author To cite this article: Pubanita Bhuyan, Pradeep K. Tripathy. Study on the Condensation of Different Hydroxy Aromatic Aldehydes with 2-Substituted 2-Oxazolin- 5-ones Generated in situ. American Journal of Heterocyclic Chemistry. Vol. 5, No. 1, 2019, pp. 1-3. doi: 10.11648/j.ajhc.20190501.11 Received: January 25, 2019; Accepted: March 14, 2019; Published: April 8, 2019 Abstract: In view to synthesize some bioactive 2-Substituted 4-(hydroxybenzylidene)-2-oxazolin-5-ones through a disciplined route, a study on the condensation of 2-, 3- and 4- hydroxy aromatic aldehydes (6) with 2-Substituted 2-oxazolin-5- ones (5) was carried out. 2-Substituted 2-oxazolin-5-ones (5) which are also known as saturated azlactones and unstable, were generated in situ from α-N-Acylglycines (1) using various cyclising agents namely ethyl chloroformate (2), benzene sulphonyl chloride (3) and p-toluene sulphonyl chloride (4) in dry benzene in presence of triethylamine base. The hydroxyl group at 3- and 4- positions of aromatic aldehydes namely 4-hydroxy-3-methoxybenzaldehyde (6a), m-hydroxybenzaldehyde (6b)and p- hydroxybenzaldehyde (6c) produce 2-substituted 4-(p-hydroxy-m-methoxybenzylidene)-2-oxazolin-5-one (8a), 2-substituted-4 (m-hydroxybenzylidene)-2-oxazolin-5-one (8b) and2-substituted-4 (p-hydroxybenzylidene)-2-oxazolin-5-one (8c) respectively as their (Z)-isomers, whereas 2-hydroxy aromatic aldehyde namely salicylaldehydeproduces 3-N-acylaminocoumarins (9) on condensation with 2-Substituted 2-oxazolin-5-ones (5) in appreciable yields and good purity. The reaction seems to be initiated by the formation of an adduct (E)-2-substituted 4-(o-hydroxybenzylidene-2-oxazolin-5-ones (7), followed by intramolecular 1,5- bond cleavage of the 2-oxazolin-5-one ring by the vicinal phenolic group and subsequent recyclization led to the formation of resultant 3-N-acylaminocoumarins (9). It is noteworthy that free hydroxyl group bearing benzylidene moiety at 4- position of 2-oxazolin-5-ones (8) were obtained. All the steps can be carried out in one flask. Keywords: 4-(Hydroxybenzylidene) Azlactones, 3-N-Acylaminocoumarins, Cyclisingagents, Synthons, in situ 1. Introduction In connection with the synthesis of 2-substituted 4- (hydroxybenzylidene)-2-oxazolin-5-ones; for example 8, the chemistry of 3-N-acylaminocoumarins (9) was investigated. 2-Oxazolin-5-ones also called 5(4H)-Oxazolones continue to attract the attention of chemists because of their usefulness as synthons and their different kinds of pharmacological and biological activities [1]. Recently the anticancer activities of some 4-(hydroxybenzylidene)-2-oxazolin-5-ones were also reported [2]. Acetic anhydride-mediated condensation of hippuric acid (1b) with salicyldehyde (6d) is known [3, 12-14] to give a mixture of products 3- Benzoylaminocoumarin (9b) and 4-(o- Acetoxybenzylidene)-2-phenyl-2-oxazolin-5-one from which 9b can be separated. However, this reaction was unsuccessful with aceturic acid (1a). The condensation of hippuric acid (1b) with 3- or 4- hydroxybenzaldehydes (6b or 6c ) in the presence of acetic anhydride and fused sodium acetate afforded 4- (acetoxybenzylidene)-2-phenyl-2-oxazolin-5-one as a major product where –OH group remained blocked by acetyl group [3, 12]. In order to get free –OH group in benzylidene moiety at 4-position of the unsaturated azlactone8, a facile and convenient route was developed (Figure 1).