Process for the manufacture of a hair dye product containing 5,6-dihydroxyindole
US5704949A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 16, 1996 |
| Grant date | Jan 6, 1998 |
| Priority date | — |
| Expiry date | Feb 16, 2016 |
Classification
- Technology area (CPC A)Human Necessities
- CPC primaryA61K8/492
- WIPO fieldPharmaceuticals
- WIPO sectorChemistry
Abstract
The present invention is directed to the preparation of an aqueous hair dyeing composition containing an effective hair dyeing amount--at least 2 mg/ml--5,6-dihydroxyindole (DHI). An aqueous hair dyeing composition is produced by reacting under essentially anaerobic conditions dopa or a salt thereof with an alkali metal ferricyanide oxidant in an aqueous reaction medium to obtain dopachrome, and permitting the dopachrome to undergo rearrangement in the aqueous medium to form 5,6-dihydroxyindole, said rearrangement being conducted in the substantial absence of oxidant, the aqueous medium being buffered by sufficient buffering agent to maintain a pH of from about 4.5 to about 9 for the reaction medium throughout the series of reactions that take place thereafter, removing the ferrocyanide species present in the aqueous system, and lastly, charging the composition into a suitable container.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.