Organic compounds -- part of the class 532-570 series – Organic compounds – Chalcogen in the nitrogen containing substituent
Patent
1983-12-02
1986-12-30
Raymond, Richard L.
Organic compounds -- part of the class 532-570 series
Organic compounds
Chalcogen in the nitrogen containing substituent
760386, 760388, 760391, 544165, 548574, 548577, C09B 1110, C07D20904, C07D26530, C07D20918
Patent
active
046329870
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a process for the preparation of triarylmethane compounds. More particularly, it relates to such a process in which a benzene or naphthalene compound is formylated and the resulting intermediate product is uninterruptedly, or without isolating it, condensed with a benzene or naphthalene compound to form a triarylmethane derivative.
BACKGROUND ART
Triarylmethane compounds are known as Leucotriarylmethane dyes which include, for example, Leucomalachite Green, Leucocrystal Violet and the like. Recently, these compounds have come to be useful as dye precursor for pressure-sensitive or heat-sensitive recording paper.
Conventionally, there have been two typical methods for the synthesis of triarylmethane compounds. By way of example, the methods for the synthesis of Leucocrystal Violet (4,4',4"-tris-dimethylaminotriphenylmethane) are represented by the following two equations. ##STR1## Other triarylmethane compounds can also be synthesized according to similar procedures.
In the prior art, the aromatic aldehyde used as the starting material in the method (A) is generally prepared by the Vilsmeyer process. Specifically, an aromatic compound is reacted with the Vilsmeyer reagent, i.e. a complex of a formylating agent for aromatic compounds (e.g., dimethylformamide, diethylformamide, etc.) and an acid catalyst (e.g., phosphorus oxychloride, phosphorus oxybromide, phosgene, thionyl chloride, etc.) to form an aromatic aldehyde. Then, the catalyst is hydrolyzed and the reaction system is neutralized by the addition of an alkaline substance. Thereafter, the aromatic aldehyde is separated by filtration, washed and then subjected to further purification, if necessary.
In order to obtain an aromatic aldehyde by forming and isolating it according to the above-described procedure, a large amount of alkali is required to neutralize the acid catalyst. Moreover, the resulting aromatic aldehyde is more or less soluble in water, which leads to an unavoidable reduction in yield.
On the other hand, the method (B) involves the problem of low purity of the hydrol derivative used as the starting material. This makes it difficult to obtain the desired triarylmethane derivative in a highly pure form.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a rational process for the preparation of triarylmethane compounds via an aromatic aldehyde compound by using an aromatic compound as the starting material.
It is another object of the present invention to provide a process for the preparation of triarylmethane compounds in which the reaction steps are continuously carried out without isolating the aromatic aldehyde compound formed as an intermediate product.
According to the present invention, there is provided a process for the preparation of triarylmethane compounds which comprises reacting a benzene or naphthalene compound with a formylating agent for such compounds in the presence of an acid catalyst to form an aromatic aldehyde compound; adding water to the reaction mixture and thereby hydrolyzing the acid catalyst without isolating the aromatic aldehyde compound from the reaction mixture; and uninterruptedly condensing the aromatic aldehyde compound with an aromatic compound in the resulting mixture to form a triarylmethane compound.
More specifically, the present process for the preparation of triarylmethane compounds comprises reacting a benzene or naphthalene compound that is substituted by a lower alkoxy group or an unsubstituted or substituted amino group and may have another substituent, with a formamide or formanilide compound in the presence of an acid catalyst to form an aromatic aldehyde; hydrolyzing the acid catalyst; and uninterruptedly reacting, in the resulting mixture, the aromatic aldehyde with an aromatic compound of the general formula pyrrolidinyl group and B represents benzene or naphthalene that may be substituted by a halogen atom, an alkyl group, an aryl group, an aralkyl group or an alkoxy group, to form a triarylmethane compound of
REFERENCES:
patent: 3739000 (1973-06-01), Lodolini et al.
patent: 4330476 (1982-05-01), Hermann
patent: 4340540 (1982-07-01), Hermann
Akahori Hiroyuki
Asano Makoto
Hasegawa Kiyoharu
Tsujimoto Michihiro
Covington Raymond
Mitsui Toatsu Chemicals Incorporated
Raymond Richard L.
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