Abstract: A Novel synthesis of l-methylamino-4-(N,N-dimethyl-N-propyl-3'-ammonium-n-propyl amino)-9,10-anthraquinone bromide, BQB (Compound VIM) is reported in the current invention.

Background of the invention:

Anthraquinones and their quarternary ammonium side chains are known in the art. These Anthraquinones are known to possess hair-dyeing properties(British patent 909700) and possess both excellent solubility in water and good absorption capacity, without dyeing the skin to any considerable extent.

US patent no 3817698 discloses another anthraquinone dye formed by covalent bond between two dye stuffs (III).

British patent 1053535 discloses the dyestuff of the formula (IV).


US patent no 5314505 discloses aminoanthraquinone hair dyes possessing a quaternary center with a lengthy aliphatic chain. These dyes were found to have higher affinity to hair, are shampoo stable and result in an uniform dyeing of hair.

This literature points to the importance of anthraquinone compounds and the continued interest in their use as dyeing materials.

US patent 5891200 discloses novel anthraquinone side chain, which is useful as hair dyes and more particularly as semi permanent blue hair dyes. The lead candidate 1-methylamino-4-(N,N-dimethyl-N-propyl-3'-ammonium-n-propylamino)-9,10-anthraquinone bromide (Compound VIII) was synthesized by following the Scheme-1.

The above synthetic sequence results in higher content of impurity VII in the final product. Prolonged reaction times, and varied modifications of the reaction conditions in no case leads to the lowering of the impurity profile to less than 0.6% -1.0 %.

Detailed Description of the invention:

The present invention is directed towards the synthesis of BQB, leading to better reactive quarternisation and hence resulting in lower reaction times and avoidance of the impurity VII.

A key intermediate n-methyl-n-propyl aminopropylamine (IX) was synthesized
following literature procedures (JACS 1946, 68, 1911) (Scheme-3). An intermediate,
1-methyl amino-4-[[3-(N-methyl-N-propyl amino) propyl] amino]-9,10-
anthraquinone (Compound X) could be obtained by reacting compound VI with an
amine derivative N,N methyl-n-propyl amino propyl amine, IX.

Suitable solvents employed for the above purpose are DMSO, DMF, NMP, DMSO
being the most preferred solvent.

Finally, BQB (Compound VIM) was isolated in high yield by quaternising the
compound X, with methyl bromide.


Experimental Procedure:
l-methylamino-4[[3-(N,N-methyl-n-propyl-(amino)propyl]amino]-9,10-athraquinone (X).
To a stirred solution of 4-bromo-l-methyl amino-9,10-anthraquinone (VI) [100g, 0.316 moles) in DMSO (370 ml) Cu2 acetate (0.0059 g) and sodium acetate (51.2 g, 0.624 moles) was added sequentially, followed by N,N methyl-n-propyl amino propyl amine (115.08). The flask was heated to 70-75°C under N2 blanket for a period of 10 hrs [TLC] and a intensely blue color transformation was noticed. The reaction mixture was quenched in water (800 ml) at 90-100°C, followed by IPA (120 ml). The contents were again heated to 75°C, followed by water addition (120 ml) & cooling to 35X to yield (X) [120 g, 95%].

1-methyl amino - (N,N-dimethyl-N-propyl-3'ammonium-n-propyl amino) -9,10-anthraquinone bromide (BQB)

To a clean IL SS hydrogenator compound X (100, 0.297 moles) NMP (335 ml) & tri butyl amine 14 ml & were sequentially added. The contents were heated under agitation (90-95T) and methyl bromide bubbled under pressure (2-2.5 Kg/Cm2). The reaction was continued for about 10 hrs and then cooled to 40°C, followed by pressure release.

IPA (Isopropyl alcohol, 230 ml) was then slowly added & the contents heated to 80°C followed by slow cooling to about 30°C. The thick reaction contents were further cooled to 5*C, filtered & washed with chilled IPA (200 ml). The crude-quaternary salt was recrystallized from n-butanol & water (790:10 ml) to yield the pure sample of BQB (85.0 g).

Claims:

1. A method of producing BQB by quaternisation of 1-methyl amino-4-[ [3-(N-methyl-N-propyl amino) propyl] amino]-9,10-anthraquinone with methyl bromide.