Process for preparing N-substituted glycine ester or N-substituted glycine, process for preparing indoxyl derivatives as well as process for preparing indigo derivatives

摘要

In the present invention there is described a process for preparing N-substituted glycine ester or N-substituted glycine of the general formula I, wherein the preparation process is characterized in that hemiacetal ester of glyoxylic acid of the general formula II, in which R is as indicated below and Ri3 represents an alkyl group with 1 up to 4 carbon atoms is brought into reaction with the amine of the general formula III, in which Ri1 is as indicated below in molar ratio 1:1 up to 1.5 in a diluent, such as alcohol, at a temperature ranging from 0 degC up to reflux temperature of the diluent used and at a pressure ranging from 0.1 up to 2 MPa. The obtained intermediate is then treated in the presence of a hydrogenation catalyst containing as an active component preferably nickel, and under reaction conditions of the diluent with hydrogen at a pressure ranging from 4 up to 8 MPa, wherein N-substituted glycine ester of the general formula I is obtained. The N-substituted glycine ester can be optionally isolated from the reaction mixture and optionally converted to a salt of a free acid. There is also described a process for producing indoxyl and indigo derivative, in which R represents hydrogen or alkyl group containing 1 up to 4 carbon atoms and Ri1 represents an alkyl group containing 1 up to 4 carbon atoms being substituted with phenyl or optionally with a hydroxy group or a phenyl group being substituted with alkoxy carbonyl or a naphthyl group.