compound of formula xi with a compound of formula xii according to the following reaction scheme str378 in which r 1 r 2 39 and hal are as defined above the reaction may be carried out under similar conditions to those employed in method 2 compounds in which y and z represent hydrogen atoms and r 2 represents an acyl group may be prepared by reacting a corresponding compound in which r 2 represents a hydrogen atom and which may have been obtained by either of foregoing methods 1 and 2 with an acid halide or anhydride of the corresponding carboxylic acid when an acid halide is used the reaction is advantageously carried out in the presence of an inert organic solvent and preferably also in the presence of an acid binding agent there is no particular limitation upon the nature of the solvent employed provided that it has no adverse effect upon the reaction examples of suitable solvents include aromatic hydrocarbons such as benzene toluene and xylene halogenated aliphatic hydrocarbons such as chloroform and trichloroethane and ethers such as diethyl ether tetrahydrofuran and dioxane where an acid binding agent is employed preferred examples include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide alkali metal carbonates such as sodium carbonate and potassium carbonate and organic bases particularly amines such as triethylamine and pyridine the reaction may suitably be carried out.