Processes for preparation of organic compounds

A method for preparing a β-lactam compound, which comprises the following steps:

• reacting a compound of Formula (2),
• wherein A represents a condensed heterocyclic group having a β-lactam ring structure, and M represents a hydrogen atom or a metal atom, in a polar organic solvent, with a 4-halogenomethyldioxolenone compound of Formula (3),
• wherein R1 and R2 each independently represent a hydrogen atom, an optionally substituted C1-C6 alkyl group or an optionally substituted phenyl group, or R1 and R2 together form an optionally substituted C3-C8 ring, and X represents a halogen atom, to result in a reaction solution containing a β-lactam compound in the polar organic solvent;
• dehydrating a polar organic solvent solution obtained as the reaction solution or obtained by working up the reaction solution, to bring the concentration of water below a given level, wherein the dehydration step comprises distilling off water together with the polar organic solvent while adding a polar organic solvent to the solution, or comprises repeating two or more cycles of adding a polar organic solvent to the polar organic solvent solution and then distilling off water together with the polar organic solvent wherein the polar organic solvent further contains an iodine compound.