. . "The solvent to be employed here is not particularly limited so long as it does not inhibit the reaction and dissolves the starting material to some extent, and may be an aliphatic hydrocarbon such as hexane, cyclohexane, heptane, ligroin or petroleum ether; an aromatic hydrocarbon such as benzene, toluene or xylene; an ether such as diethyl ether, diisopropyl ether, tetrahydrofuran, dioxane, dimet" . .