PURPOSE: To efficiently obtain β-halogeno-tert.-alkyl isocyanates useful as intermediates of rubber additives, herbicides, etc., by allowing specified tert.- alkyl isocyanates to react with gaseous hydrogen chloride, chlorinating the resultant compds. and liberating the objective βhalogenotert.-alkyl isocyanates by dehydrohalogenation.

CONSTITUTION: Tert.-alkyl isocyanates of formula I [where R1 is alkyl of halogenoalkyl and R2 is alkyl, halogenoalkyl or (halogenand/or trifluoromethyl- substd.) phenyl] are converted into the corresponding tert.-alkylcarbamoyl chlorides with gaseous hydrogen chloride and the chlorides are chlorinated with elemental chlorine under irradiation with a high pressure mercury vapor lamp or in the presence of catalysts in a suitable apparatus and the resultant β-halogeno-tert.-alkyl isocyanates of formulas II (where X is Cl and Y is H or Cl) are liberated by dehydrohalogenation at elevated temp.