PROCESS FOR THE PREPARATION OF INDIGO COMPOUNDS

摘要

An indigo compound is prepared from a corresponding indole compound which is unsubstituted at the 2and 3- positions. The indole compound and an organic hydroperoxide are reacted in the presence of a catalyst which is a metal selected from the group consisting of the metals of Groups 4, 5 and 6 of the periodic table or a compound of the metal. The reaction is conducted while taking out water from a reaction system, the water being that introduced in the reaction system or formed during the reaction, or while controlling the amount of water, which is introduced in the reaction system, at a level not greater than 1 mole per mole of the indole compound.