Process for methylating a hindered nitrogen atom in an inert non

Details Process for methylating a hindered nitrogen atom in an inert non Process for methylating a hindered nitrogen atom in an inert non

1989-11-21

1993-08-24

Richter, Johann

Organic compounds -- part of the class 532-570 series

Organic compounds

Four or more ring nitrogens in the bicyclo ring system

544113, 544209, 544212, 540598, C07D25132

Patent

active

052390713

ABSTRACT:
A process for methylating the N.sup.4 atom of a polysubstituted piperazine or piperazin-2-one ("PSP") is effective despite using a much smaller molar excess of formaldehyde and formic acid than dictated by a conventional Eschweiler-Clarke reaction. Particularly in a complex amine in which the PSP substituent is connected to a triazine ring which in turn may be connected to a N atom of an acyclic polyamine, the molar ratio of NH groups:HCHO:HCOOH is in the range from about 1:1:1 to 1:1.5:1.5, the amount of HCHO and HCOOH being sufficient to methylate at least the >NH groups of said PSP substituent if the complex amine contains terminal --NH groups. The same range of molar ratio is maintained when the total number of NH groups to be methylated includes the terminal --NH groups. The effectiveness of the process is attributed to use of an alkylbenzene solvent in which reaction with only a slight excess of HCHO and HCOOH proceeds apace, and in which solvent the methylated product remains dissolved.

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Pine et al. J. Org. Chem. vol. 36, No. 6, 829-832 (1971).

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