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3-(2-Substi tuted benzalimino-4-thiozolyl)-coumarins (1) on reduction with N a B H 4 resulted in the formation of corresponding 3-(2-o-hydroxy benzyl hydrazino-4-thiazolyl)coumarins (2). These on condensation with formaldehyde gave the cycloproducts 3-(2-( l ,3-benzoxazin-3-yl)-4thiazoIyl)coumarins (3). Introduction Coumarin nucleus is found in a variety of natural products which inhibit various pharmacological effects. Derivatives of coumarin also form compounds of important drugs having varied properties. There are excellent monographs and reviews articles" describing the structure, synthetic reactions and properties of coumarin. Numerous reports have appeared in the literature describing antimicrobial,' antiradiation and antiparasitic properties of the thiazole ring. Several 1,3-benzoxazine derivatives reported in the literature were found to possess antireserpine, analgesic, antiinflammatory, tranquilizing, sedative, bactericidal, bacteriostatic," smooth muscle relaxant and spermicidal activities. They are also used in the preparation of polymers. These compounds can be prepared in one-step by Mannich reaction of a primary amine with the appropriate phenol in presence of excess of formaldehyde. However, the yields in this method are some what less. Besides, some other methods for 17 18 the preparation of these compounds are reported. ' Prompted by the above observations and in continuation of our search for biologically active nitrogen and sulphur heterocyclics' it was decided to synthesize these heterocyclic coumarins. Results and Discussions Realising the importance of 1,3-benzoxazines during investigations on internal Mannich reactions, we tried to develop a new route for the synthesis of the title compounds 3. The starting compound 3-(2-amino-4-thiazolyl)coumarins were prepared according to the procedure described in the literature. 3-(2-o-hydroxybenzalimino-4thiazolyl)coumarins (1) have been obtained by condensation of 3-(2-amino-4thiazolyl)courmain with aromatic aldehydes. These compounds (1) on reduction with sodium borohydride in methanol gave 3-(2-o-hydroxy benzylamino-4thiazolyl)coumarins (2). Compounds 2 under went internal Mannich reaction when refluxed with formaldehydes (37%) in ethanol for 4-5 hours to give desired 3-(2-(l,3benzoxazin-3-yl)-4-thiazolyl coumarins 3 in excellent yields (scheme-1). The structures of newly synthesized compounds have been confirmed by analytical (Table-1) and spectral data (IR, 'H NMR and Mass). 429 Unauthenticated Download Date | 6/8/19 10:50 PM Vol. 10, No. 6, 2004 Facile synthesis of some new 3-(22-l ,3-benzoxazin-3-yl)-4-thiazolyl coumarins 430 Unauthenticated Download Date | 6/8/19 10:50 PM Μ.Μ.Μ. Redely and V.R.Rao Heterocyclic Communications

FACILE SYNTHESIS OF SOME NEW 3-(2-(1,3-BENZOXAZIN-3-YL)- 4-THIAZOLYL COUMARINS