it provides an alterative isolation procedure it is known that the product bos na can be isolated by evaporation of an aqueous phase the present invention also provides two alternatives in which the product is precipitated from water which can be induced by the following ways for example a bos na may be isolated from water by precipitation by salting out e g with sodium chloride i e nacl and cooling and b bos ba or bos ca may be isolated based on their low solubility and can be quantitatively precipitated from water separation of bos as the barium ba or calcium ca salt facilitates industrial scale preparation of this intermediate once the salt precipitates it may be washed with water to reduce the inorganic salt content a product contaminated with inorganic salts is usually more hygroscopic than the pure compound and its use is problematic in the pocl 3 reaction the present invention is described below in detail with reference to examples the present invention is by no means restricted to these specific examples the experiments are summaried as followed 0037 table 2 boa yield and side products under various experimental conditions exp boa yield unreacted no solvent base oxime 4 hc reference 1 ethanol na 68 3 19 8 1 2 ethanol water na acetate 48 7 30 8 2 3 ethanol na 2 co 3 82 0 2 17 5 present procedure 4 methanol na 2 co 3 87 5 1 1 7 5 present procedure 5 n buoh na 2 co 3 98 0 9 1 present procedure 6 n buoh k 2 co 3 82 9 17 present procedure 4 hydroxy coumarin 10 grams was added to the mixture of hydroxyl amine hydrochloride 15 grams and sodium carbonate 23 grams.