GB806729A - Halogenated benzo-1:3-oxazine derivatives - Google Patents

Abstract

The invention comprises compounds of the general formula <FORM:0806729/IV (b)/1> (wherein R1 is hydrogen or a halogen atom, R2 is a halogen atom and n is 1 or 2) and their preparation by condensation of salicylamide or a 5-halogeno-salicylamide with one of the following reagents under the conditions specified: (a) a b -halo-propionaldehyde or halo-acetaldehyde in an inert organic solvent, e.g. benzene or chloroform, which may act as a water entrainment agent, and in the presence of a condensation agent such as a hydrogen halide gas, concentrated sulphuric acid or a weak acid such as benzene- or toluene-sulphonic acid or phosphoric acid; (b) an acetal of the aldehydes of (a) in the presence of a condensation agent, e.g. hydrogen halide gas or concentrated sulphuric acid, and an alcohol binding agent, e.g. glacial acetic acid, advantageously in an inert solvent, e.g. chloroform; (c) a compound R3-O-CH2-CH2-CHO (wherein R3 is a lower alkyl radical) or an acetal thereof in an inert organic solvent, e.g. chloroform or benzene, in the presence of a hydrogen halide and preferably also in presence of an alcohol binding agent such as glacial acetic acid; and (d) acrolein in an inert organic solvent, e.g. glacial acetic acid, with or without chloroform, in the presence of a condensation agent, e.g. a hydrogen halide gas. Methods (c) and (d) cannot be used to prepare compounds wherein n is 1. The acetals used in (b) may be prepared in situ, e.g. by the dropwise addition of acrolein to a lower alcohol in chloroform saturated with a hydrogen halide gas. The invention also comprises the preparation of the compounds (I) wherein R2 is iodine, by reacting the compounds, wherein R2 is chlorine or bromine, with an alkali metal iodide, e.g. KI or NaI. Examples describe the preparation of 4 - oxo - 2 - (b - chloroethyl) - 2 : 3 - dihydro - (benzo - 1 : 3 - oxazine) and the corresponding 6-bromo- and 6-chloro-compounds, 4-oxo-2-(b -bromoethyl) - 2 : 3 - dihydro - (benzo - 1 : 3 - oxazine), 4 - oxo - 2 - chloromethyl - 2 : 3 - dihydro - (benzo - 1 : 3 - oxazine), 4 - oxo - 6 - chloro - 2 - bromomethyl - 2 : 3 - dihydro - (benzo - 1 : 3 - oxazine) and 4 - oxo - 2 - (b - iodoethyl) - 2 : 3 - dihydro - (benzo - 1 : 3 - oxazine) by one or more of the processes of the invention, glacial acetic acid being added as a catalyst in the preparation of the fourth named of these compounds by method (a).