US 2783227 A
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United States. Patent v g 7 2,783,227 NAPHTHOYL LEUCO METHYLENE BLUE 3 Claims. (Cl. 260-243) This invention relates to the substantially light-stable leucomethylene blue derivative -naphthoyl-3,7-bis (dimethylamino)phenothiazine, having the structure where R is taken from the group consisting of l-naphthoyl and 2-naphthoyl.
The known leucomethylene blue compound IO-benzoyl- 3,7-bis(dimethylamino)phenothiazine has been used as a color reactant in connection with manifold sheets such as those described in the United States Patent No. 2,646,367, which issued on the application of Chester Davis and Ned A. Thacker on July 21, 1953. In that patent, there is disclosed a manifold sheet having a colorless transfer coating on one side, the coating being made of wax and an oil having dissolved in it the colorless color reactant crystal violet lactone, which is 3,3-bis- (p-dimethylaminophenyl)-6-dimethylaminophthalide, and the beforementioned benzoyl leucomethylene blue. If such a manifold sheet is placed with the transfer coating in contact with the surface of a copy sheet sensitized with particles of attapulgite, halloysite, or equivalent acid claylike material, and an impression is made by printing or writing on the top side of the manifold sheet, the color reactants will be transferred with the oil onto the sensitized surface of the copy sheet. The crystal violet lactone will immediately turn dark blue when coming into contact with the sensitizing clay-like material, thus manifesting whatever was printed or written on the top sheet. After prolonged exposure to light, this dark blue color will fade, but the benzoyl leucomethylene blue will be developing a blue-green color, so that the printed or Written matter will not be lost.
The benzoyl leucomethylene blue has one characteristic in its disfavor, and that is that it slowly decomposes to the blue-green color on exposure to light, which means that, if the transfer coating is exposed to light for a long time, it turns to an undesirable blue-green color.
Therefore, it is the object of this invention to provide more light-stable naphthoylated derivatives of leucomethylene blue.
The manufacture of l0-(2-naphthoyl)-3,7-bis (dimethylamino)phenothiazine may be started with the commercially available zinc chloride double salt of leucomethylene blue, having the structure To 35 grams (0.0706 mole) of the zinc chloride double salt of leucomethylene blue is added 97 grams (1.25 moles) of pyridine in a three-necked, round-bottom flask fitted with a mechanical stirrer, a thermometer, and a reflux condenser. To the above mixture is added slowly 25 grams (0.131 mole) of 2-naphthoyl chloride while 2,783,227 Patented Feb. 26, 1957 2 stirring. The reaction mixture is refluxed gently for one hour. The resultant hot reaction mixture then is poured into one liter of cold water andmechanically stirred for one half hour. The brown semi-solid precipitate which forms is washed with water and thereafter stirred with 17.5 grams of sodium hydroxide dissolved in one half liter of water for one half hour. The alkaline solution then is decanted ofi, and the semi-solid residue is washed with water and extracted with 2.2 liters of hot benzene. The dark benzene solution then is treated with fullers earth and filtered. The resultant amber filtrate is concentrated to 400 milliliters and precipitated with petroleum ether.
The resulting final product, l0-(2-naphthoyl)-3,7-bis- (dimethylamino)phenothiazine, is a light yellow crystalline material having the following structure:
S Ha)zN s mom).
In making the l-naphthoyl derivative, IO-(I-naphthoyl)-3,7-bis(dimethylamino)phenothiazine, having the i in which R is taken from the group consisting of l-naphthoyl and 2-naphthoyl.
2. The substantially light-stable leucomethylene blue derivative 10 (2-naphthoyl) 3,7 bis(dimethylamino)- phenothiazine, having the following structure:
3 3. The substantially light-stable leucomethylene blue derivative lO-(l-naphthoyl) 3,7 bis(dimethylamino)- phenothiazine, having the following structure:
S 113,721 an 1 6 \NC $12,300 7 i 5 3 5 125,275
FQREIGN PATENTS Germany Sept. 28, 1900 Belgium July 15, 1952 Great Britain Mar. 2, 1955