Alternatively, the reaction mixture may be concentrated under reduced pressure to yield a solid, which solid may then be triturated in the presence of a suitable solvent, for example diethyl ether.A compound of formula (IIB) wherein L is a halogen atom may be prepared by reaction of a compound of formula (IX): R2???OG (IX) wherein R2 is as hereinbefore defined for a compound of formula (I) and OG