Process for methylating a hindered nitrogen atom in an inert non-aqueous solvent
US5239071A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 21, 1989 |
| Grant date | Aug 24, 1993 |
| Priority date | — |
| Expiry date | Nov 21, 2009 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC07D403/14
- WIPO fieldOrganic fine chemistry
- WIPO sectorChemistry
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.