Thus for example, the reaction may be carried out in a solvent, for example an inert organic solvent such as an ether, e.g. a cyclic ether such as tetrahydrofuran, an amide, e.g. a substituted amide such as dimethylformamide, or a halogenated hydrocarbon such as dichloromethane, at a low temperature, e.g. -30??? C. to ambient temperature such as -20??? C. to 0??? C., optionally in the presence of