Synthesis of 4H-3,1-benzoxazin-4-one 2-phenyl Using Cyanuric Chloride as a Cyclization Agent

The preparation of different derivatives of benzoxazinone can be considered important because they have different kinds of pharmaceutical, agricultural and industrial applications [1,2,3,4]. The synthesis of benzoxazinone derivative, 4H-3,1-benzoxazin-4-one 2-(N-phthaloylmethyl), was reported previously by our team [5]. In this paper we have used the same method to synthesize 4H-3,1-benzoxazin-4-one 2-phenyl 5. This synthesis occurs in two steps: In the first step, anthranilic acid 1 (4.11g) in 40 ml chloroform was mixed with 4.15 ml anhydrous triethylamine and 3.48 ml benzoyl chloride 2 in 10 ml chloroform. In the second step, the resulting benzamid 3 (2.41 g) mixed with 100 ml anhydrous toluene, 1.52 ml triethylamine and 1.84 g cyanuric chloride 4 is refluxed for one week. After purification, drying with magnesium sulfate, the resulting benzoxazinone 5 as a final product is recrystallized in 30% ether-chloroform solution. Yield 67.8 % (63% overall)

For the compound 3:

¹H-NMR (CDCl₃): δ= 7.10-9.13 (m, 9H, Ar-H; NH); 12.1-12.3 (broad singlet,-COOH).

IR (KBr, cm⁻¹): 2460 – 3115; 1680; 1639.

For the product 5

Melting point: 122-124°C (lit. 123-125) [6].

¹H-NMR (CDCl₃): δ= 7.25-8.73 (m, 9H, Ar-H).

IR (KBr, cm⁻¹): 1760; 1608.

Elemental Analysis: Calculated for C₁₄H₉NO₂ (223.23): C, 75.33%; H, 4.06%; N, 6.27%; O, 14.33. Found: C, 75.01%; H, 4.26%; N, 6.3%; O, 14.43%.