Thus for example the reaction may be carried out in a solvent, for example an alcohol, e.g. methanol or ethanol, at a temperature from around ambient to the reflex temperature, optionally in the presence of a base, e.g. an organic base such as an amine, e.g. triethylamine or N,N-diisopropylethylamine, or a cyclic amine, such as N-methylmorpholine or pyridine. [0177] In a further example compounds