Method for the phosgenation of compounds comprising hydroxyl, thiol, amino and/or formamide groups

A method for the reaction of a first compound with a second compound, wherein the first compound has a hazardous substance classification, in accordance with GHS, of GHS06 and can be obtained from the reaction of at least one first fluid precursor compound and one second fluid precursor compound, and wherein the second compound is capable of entering into a chemical reaction with the first compound, comprises the steps: (I) providing a liquid phase, which comprises the second compound, in a reactor with an upper end and a lower end as viewed in the direction of gravitational force; (II) providing a contact pipe (100, 110), which has an upper end and a lower end, in the reactor, wherein the lower end of the contact pipe dips into the liquid phase comprising the second compound and, in the contact pipe, there is provided a catalyst bed which is designed to catalyze the reaction of the first and second precursor compounds to form the first compound; (III) introducing the first and second precursor compounds thro