CA1139764A - Process for the manufacture of bis- benzoxazolyl-stilbene compounds - Google Patents
Process for the manufacture of bis- benzoxazolyl-stilbene compoundsInfo
- Publication number
- CA1139764A CA1139764A CA000345572A CA345572A CA1139764A CA 1139764 A CA1139764 A CA 1139764A CA 000345572 A CA000345572 A CA 000345572A CA 345572 A CA345572 A CA 345572A CA 1139764 A CA1139764 A CA 1139764A
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- Prior art keywords
- formula
- benzoxazolyl
- bis
- aminophenol
- acid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Heterocyclic Carbon Compounds Containing A Hetero Ring Having Nitrogen And Oxygen As The Only Ring Hetero Atoms (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Process for the manufacture of bis-benzoxazolyl-stilbene compounds which comprises the chlorination in an inert organic solvent of benzoxazolyl-stilbene carboxylic acid, addition of a solution of an aminophenol in an aprotic, dipolar solvent to the acid chloride thus obtained and subsequent cyclization in the presence of an acid catalyst of the acyl compound obtained. The improved process provides products of high purity in a one-stage process so that the products may be directly used as optical brighteners without previous purification by recrystallization.
Process for the manufacture of bis-benzoxazolyl-stilbene compounds which comprises the chlorination in an inert organic solvent of benzoxazolyl-stilbene carboxylic acid, addition of a solution of an aminophenol in an aprotic, dipolar solvent to the acid chloride thus obtained and subsequent cyclization in the presence of an acid catalyst of the acyl compound obtained. The improved process provides products of high purity in a one-stage process so that the products may be directly used as optical brighteners without previous purification by recrystallization.
Description
3~'7~
- 2 ~ HOE 78/F 044 Bis-benzoxazolyl-stilbenes have gained technical importance as optical brighteners, for example as spin brighteners or as so-components in optical brighteners for textile materials.
Up to now, they have been prepared, for example as described in US-PS 3,586,673, by reacting 4-benzoxazolyl-2,4'-stilbene-carboxylic acid in 1,2,4-trichlorobenzene with phosphorus oxychloride to give the acid chloride, sub-se~uently addin~ a solid aminophenol and heating the reac-tion mixture. For purification the crude products obtained in this manner must be recrystallized repeatedly. A similar process is described in ~A-PS 23,028/69.
One-stage processes for the manufacture of the above eompounds have been described in DE-OS 2,247,791, method t5 A~ pages 16-17 and in DE-OS 2,315,955, Example 5. In both eases the acid chloride is reacted with aminophenol in tri-ehlorobenzene and the amine formed is subjected to cycli-zation in the reaction mixture without previous lsolation.
In DE-OS 2,315~955 the aminophenol is dissolved in pyridine and the acid chloxide is added in the orm of a solution ~n ~richlorobenzene. During the course o~ the reaction the pyridine distils off. In the process of DE-OS
2,247,791 the aminophenol is added in the form of a hot solution in trichlorobenzene. The processes yield products that are highly contaminated and that must be purified by recrystallization.
It has now been found, surprisingly, that bis-benzoxa-zolyl-stilbenes of the formula defined below can be ob-tained in a high purity in a one-stage process if a solution of aminophenol in an aprotic, dipolar solvent is added to the solution of a benzoxazolyl-stilbene-carboxylic acid in an inert solvent. In this manner products are ob-tained which can be directly used as optical brigtheners without previous purification by recrystallization.
It is the objective of the present invention to provide a simple and economical process for the manufacture o bis-benzoxazolyl-stilbene compounds according to which the desired products are obtained in a high purity and in a '3'7~
Up to now, they have been prepared, for example as described in US-PS 3,586,673, by reacting 4-benzoxazolyl-2,4'-stilbene-carboxylic acid in 1,2,4-trichlorobenzene with phosphorus oxychloride to give the acid chloride, sub-se~uently addin~ a solid aminophenol and heating the reac-tion mixture. For purification the crude products obtained in this manner must be recrystallized repeatedly. A similar process is described in ~A-PS 23,028/69.
One-stage processes for the manufacture of the above eompounds have been described in DE-OS 2,247,791, method t5 A~ pages 16-17 and in DE-OS 2,315,955, Example 5. In both eases the acid chloride is reacted with aminophenol in tri-ehlorobenzene and the amine formed is subjected to cycli-zation in the reaction mixture without previous lsolation.
In DE-OS 2,315~955 the aminophenol is dissolved in pyridine and the acid chloxide is added in the orm of a solution ~n ~richlorobenzene. During the course o~ the reaction the pyridine distils off. In the process of DE-OS
2,247,791 the aminophenol is added in the form of a hot solution in trichlorobenzene. The processes yield products that are highly contaminated and that must be purified by recrystallization.
It has now been found, surprisingly, that bis-benzoxa-zolyl-stilbenes of the formula defined below can be ob-tained in a high purity in a one-stage process if a solution of aminophenol in an aprotic, dipolar solvent is added to the solution of a benzoxazolyl-stilbene-carboxylic acid in an inert solvent. In this manner products are ob-tained which can be directly used as optical brigtheners without previous purification by recrystallization.
It is the objective of the present invention to provide a simple and economical process for the manufacture o bis-benzoxazolyl-stilbene compounds according to which the desired products are obtained in a high purity and in a '3'7~
- 3 - HOE 78/F 044 good yield. According to the invention this objective i5 obtained by adding the aminophenol not in solid form but in the form of a solution in an aprotic,dipolar solvent.
It i5, therefore, the object of the present invention to provide a process for the manufacture of bis-benzoxa-zolyl-stilbene compounds of the formula I
R~
in which R , R and R , independent of one another, denot~
hydrogen, C1-Cg alkyl, carbo-C1-C4 alkoxy and tri3fluoro-methyl, at least two of the radicals R , R and R
being hydrogen, by chlorination of an acid of the formula II
1 ~ ~ _CEI=CH- ~ _COOH ~II) in which R1 is as defined under formula I, in an inert organic solvent ancl subsequent reaction with an amino-phenol of the formula III
2 ~ R2 (III) Ho~R3 in which R2 and R3 are as defined under formula I, which comprises adding the aminophenol in the form of a solution in an aprotic, dipolar solvent, preparing the compound of the formula IV 2 R1 ~ ~ ~ ~ CH=~H- ~ C ~ (IV) in which R1, R2 and R3 are as defined under formula I by acylation and preparing therefrom the compound of the 7~
It i5, therefore, the object of the present invention to provide a process for the manufacture of bis-benzoxa-zolyl-stilbene compounds of the formula I
R~
in which R , R and R , independent of one another, denot~
hydrogen, C1-Cg alkyl, carbo-C1-C4 alkoxy and tri3fluoro-methyl, at least two of the radicals R , R and R
being hydrogen, by chlorination of an acid of the formula II
1 ~ ~ _CEI=CH- ~ _COOH ~II) in which R1 is as defined under formula I, in an inert organic solvent ancl subsequent reaction with an amino-phenol of the formula III
2 ~ R2 (III) Ho~R3 in which R2 and R3 are as defined under formula I, which comprises adding the aminophenol in the form of a solution in an aprotic, dipolar solvent, preparing the compound of the formula IV 2 R1 ~ ~ ~ ~ CH=~H- ~ C ~ (IV) in which R1, R2 and R3 are as defined under formula I by acylation and preparing therefrom the compound of the 7~
- 4 - HOE 78/F 04A
~ormula I ~y cyclization after addition of an acid catalyst.
To carry out ~he process of the invention the compound of the formula II is reacted in an inert or~anic solvent, for example o-dichlorobenzene, trichlorobenzene, tetra-; hydronaphthalene, optionally with the addition of acatalyst, for example a small amount of dimethyl formamide, with a chlorination agent such as thionyl chloride to give the acid chloride. The excess amount of chlorination agent is subsequently distilled off up to an internal temperature of 140 to 160C, a complete removal possibly being promoted by passing an N2 current over the reaction mixture. To this mixture, which is either a solution or a suspension, a solution of a compound of the formula III in an aprotic, dipolar solvent is then added dropwise at a temperature of from 100 to 200C, preferably 150 to 160C and stirring is continued at 100 to 200C, preferably 130 to 160C until the conversion into the compound of the ~ormula IV is complete, which can be percei~ed by the termination of the hydrogen chloride generation.
5uitable aprotic solvents are ~,N-dialkyl-carboxylic acid amides, for example dimethyl formamide, N-methyl-pyrrolidone, or hexamethyl-phosphoric acid trisamide, preferably, however, N-methylpyrrolidone. The aprotic, dipolar solvent (solvent B) is used in an amount of from 3 to 30 and preferably 5 to 15-~ by volume, calculated on the amount of inert organic solvent (solvent A) used for the reaction of the compound of the formula II. As men-tioned above, suitable inert organic solvents are, for example, tetrahydronaphthalene, decahydronaphthalene or methylnaphthalene, the boiling point of which should not be below the reaction temperature.
The cyclization of compound IV to give compound I
is carried out without intermediate isolation by heating the reaction mixture to a temperature of from 150 to 250C, preferably the boiling point of solvent A and op-tionally in the presence of an acid catalyst. Suitable catalysts are, for example, boric acid, zinc chloride, . -.
.:
' ,
~ormula I ~y cyclization after addition of an acid catalyst.
To carry out ~he process of the invention the compound of the formula II is reacted in an inert or~anic solvent, for example o-dichlorobenzene, trichlorobenzene, tetra-; hydronaphthalene, optionally with the addition of acatalyst, for example a small amount of dimethyl formamide, with a chlorination agent such as thionyl chloride to give the acid chloride. The excess amount of chlorination agent is subsequently distilled off up to an internal temperature of 140 to 160C, a complete removal possibly being promoted by passing an N2 current over the reaction mixture. To this mixture, which is either a solution or a suspension, a solution of a compound of the formula III in an aprotic, dipolar solvent is then added dropwise at a temperature of from 100 to 200C, preferably 150 to 160C and stirring is continued at 100 to 200C, preferably 130 to 160C until the conversion into the compound of the ~ormula IV is complete, which can be percei~ed by the termination of the hydrogen chloride generation.
5uitable aprotic solvents are ~,N-dialkyl-carboxylic acid amides, for example dimethyl formamide, N-methyl-pyrrolidone, or hexamethyl-phosphoric acid trisamide, preferably, however, N-methylpyrrolidone. The aprotic, dipolar solvent (solvent B) is used in an amount of from 3 to 30 and preferably 5 to 15-~ by volume, calculated on the amount of inert organic solvent (solvent A) used for the reaction of the compound of the formula II. As men-tioned above, suitable inert organic solvents are, for example, tetrahydronaphthalene, decahydronaphthalene or methylnaphthalene, the boiling point of which should not be below the reaction temperature.
The cyclization of compound IV to give compound I
is carried out without intermediate isolation by heating the reaction mixture to a temperature of from 150 to 250C, preferably the boiling point of solvent A and op-tionally in the presence of an acid catalyst. Suitable catalysts are, for example, boric acid, zinc chloride, . -.
.:
' ,
- 5 ~ HOE 78/F 044 p-toluenesulfonic acid and polyphosphoric acids, which are preferably used in an amount of from 0.5 to 5 %, calculated on the amount of compound II used.
When the cyclization is terminated, which can be perceived by the termination of the water separation, the reaction product is isolated in usual manner, for example by suction filtration after cooling to room temperature~
Prior to filtration a low molecular weight alcohol, for example methanol or ethanol, may be added to the reaction mixture.
~ he compounds of the formula IV used as starting components are known from literature and can be produced by processes described in 1iterature (cf. JA-PS 40,581/65, JA-PS 44-6979, JA-PS 7045/68, DE-OS 2,306,050, DE-OS
1,594,829 and DE-OS 2,129,818).
Preferred compounds to be produced by the process described above are compounds of the formula I a ~3 ~ ~ 0~3 ' in which R1 , R2 , R3 and R4 , independent of one another, denote hydrogen or C1-C4 alkyl and at least one of the radicals R to R is hydrogen.
In the process according to the invention the compounds of the formula I are obtained in an excellent purity and in an almost quantitative yield. Normally, no further purification by recrystallization is necessary. This is an especially important feature as bis-benzoxazolyl-stilbenes of the formula I generally have a poor solubility and, therefore, large amounts of solvent would be required for recrystallization. As compared therewith, all known processes, in which the aminophenol is not added in the form of a solution in an aprotic, dipolar solvent, yield dark yellow or brown products which possess a distinctly .~ lesser brightening effect and, therefore, have to be '7t;'~
When the cyclization is terminated, which can be perceived by the termination of the water separation, the reaction product is isolated in usual manner, for example by suction filtration after cooling to room temperature~
Prior to filtration a low molecular weight alcohol, for example methanol or ethanol, may be added to the reaction mixture.
~ he compounds of the formula IV used as starting components are known from literature and can be produced by processes described in 1iterature (cf. JA-PS 40,581/65, JA-PS 44-6979, JA-PS 7045/68, DE-OS 2,306,050, DE-OS
1,594,829 and DE-OS 2,129,818).
Preferred compounds to be produced by the process described above are compounds of the formula I a ~3 ~ ~ 0~3 ' in which R1 , R2 , R3 and R4 , independent of one another, denote hydrogen or C1-C4 alkyl and at least one of the radicals R to R is hydrogen.
In the process according to the invention the compounds of the formula I are obtained in an excellent purity and in an almost quantitative yield. Normally, no further purification by recrystallization is necessary. This is an especially important feature as bis-benzoxazolyl-stilbenes of the formula I generally have a poor solubility and, therefore, large amounts of solvent would be required for recrystallization. As compared therewith, all known processes, in which the aminophenol is not added in the form of a solution in an aprotic, dipolar solvent, yield dark yellow or brown products which possess a distinctly .~ lesser brightening effect and, therefore, have to be '7t;'~
- 6 - HOX 78/F 044 redissolved.
The following examples illustrate the invention, the parts are by weight unless otherwise stated and the melting points are not corrected.
E X A M P L E 1:
. _ __ _ _ 177 Parts of thionyl chloride are added over a period of approximately 1 hour to a suspension of 170 parts of 4-(2-benzoxazolyl-2-4'-stilbe,ne~carboxylic acid in 1150 parts of tetrahydronaphthalene, which suspension contains ~ parts of dimethyl formamide. The reaction mixture is heated to 110C within a period of about 2 hours and stirring at that temperature is continued for 1 hour. Next, the thionyl chloride in excess is distilled off in a nitrogen current down to an internal temperature of 150C. At said temperature a solution of 65 parts of 2-amino-4-methylphenol iIl 125 parts of N-methylpyrrolidone is added dropwise and the reaction mixture is slowly heated to 170C within 3 hours. After addition of 5 parts of p-toluene-sulfonic acid, the mixture is heated to ~0 reflux temperature and the reaction water is separated over a water separator. When the water separation is terminated, the reaction mixture is cooled to 100C, 320 parts of methanol are added dropwise and the mixture is refluxed for another hour. After cooling to room tempe-rature, the mixture is filtered with suction and theresidue is washed with methanol. After drying, 206 g (96 ~ of theory) of the compound , ~ > ~ CII=CH- ~ _,,N ~ ~ C~I3 are obtained in the form of a light yellow powder having the following melting properties:
the product sinters at 266 to 270C, it has a liquid-crystalline transition at 316 to 321C and it melts above 370C. The tinctorial properties can be improved slightly only by repeated recrystallization from N-methylpyrrolidone with clarification with active carbon.
, .. - :
' ' '7~
The following examples illustrate the invention, the parts are by weight unless otherwise stated and the melting points are not corrected.
E X A M P L E 1:
. _ __ _ _ 177 Parts of thionyl chloride are added over a period of approximately 1 hour to a suspension of 170 parts of 4-(2-benzoxazolyl-2-4'-stilbe,ne~carboxylic acid in 1150 parts of tetrahydronaphthalene, which suspension contains ~ parts of dimethyl formamide. The reaction mixture is heated to 110C within a period of about 2 hours and stirring at that temperature is continued for 1 hour. Next, the thionyl chloride in excess is distilled off in a nitrogen current down to an internal temperature of 150C. At said temperature a solution of 65 parts of 2-amino-4-methylphenol iIl 125 parts of N-methylpyrrolidone is added dropwise and the reaction mixture is slowly heated to 170C within 3 hours. After addition of 5 parts of p-toluene-sulfonic acid, the mixture is heated to ~0 reflux temperature and the reaction water is separated over a water separator. When the water separation is terminated, the reaction mixture is cooled to 100C, 320 parts of methanol are added dropwise and the mixture is refluxed for another hour. After cooling to room tempe-rature, the mixture is filtered with suction and theresidue is washed with methanol. After drying, 206 g (96 ~ of theory) of the compound , ~ > ~ CII=CH- ~ _,,N ~ ~ C~I3 are obtained in the form of a light yellow powder having the following melting properties:
the product sinters at 266 to 270C, it has a liquid-crystalline transition at 316 to 321C and it melts above 370C. The tinctorial properties can be improved slightly only by repeated recrystallization from N-methylpyrrolidone with clarification with active carbon.
, .. - :
' ' '7~
- 7 ~ HOE 78/F 044 E X A M P L E 2:
The reaction is carried out as described in Example 1 with the exception that 5 parts of phosphorus pentoxide are used instead of p-toluenesulonic acid. The same compound is obtained in the same quality but in a slightly smaller yield.
E X A M P L E 3:
The reaction is carried out as described in Example 1 with the exception that 1,2,4~trichlorobenzene is used as solvent instead of tetrahydronaphthalene. The same compound is obtained in an equally good quality in a yield of 92 % of the theory.
E X A M P L E 4:
In the manner described in Examples 1 to 3 further optical brighteners o the formula Ia as specified in the following table can be prepared.
, a~ ;:; ~ ~ u~ o ~ n ~ --1 C ~ r~ ~ G~ co up ~ o o ll o o o o ~ ~ ~ ~ ~ ~ ~ ~
~--~ - ~
O _ ~ ~ ~ ~ ~ ~r -1~ lo ~ W C~ O CO ~
QI ~ ~ CO Ct) 0;~ G~ CO G~
~ _ _______.
>~ ~ 0 ~ ~ ~ O ~r ~ ~; ~ t~ ~ ~ r k ~ ~'1 ~ r~l 1`'1 ~) t`') . .~ ~
\~ ~? O ' ~, ~3 ~ r~ ~ ~ r~ ~ ~7 ~r~ ~1 N ~ ~ I ~) ~ (~
~11 ''1._ ~;~ h , R; ~ ~ ~ ~ ~ ~ r U ; ~; r-l h ~ t~ ~ O
~: . . ~ _ ~ ~ ~ ~ r~ - rJo ~D O
l~ ~ ~ rl ~ 1 ~ . ~ .
~ ~ dP ~
. .. _ .
~: ~ . ~ ~
__ ~1 _ ~ ~ 5 X 3~
~ _ _ ,~ _ _ ~ r~
~ ~ }
_ ___ ~ ' ~
_ __. ______ . _ .
~;
X ~ O -. . ,. - _____.__________ __ _ .~ .
. . .
- .
.. . ' ~ ~ ' ' : ' ' , :.
The reaction is carried out as described in Example 1 with the exception that 5 parts of phosphorus pentoxide are used instead of p-toluenesulonic acid. The same compound is obtained in the same quality but in a slightly smaller yield.
E X A M P L E 3:
The reaction is carried out as described in Example 1 with the exception that 1,2,4~trichlorobenzene is used as solvent instead of tetrahydronaphthalene. The same compound is obtained in an equally good quality in a yield of 92 % of the theory.
E X A M P L E 4:
In the manner described in Examples 1 to 3 further optical brighteners o the formula Ia as specified in the following table can be prepared.
, a~ ;:; ~ ~ u~ o ~ n ~ --1 C ~ r~ ~ G~ co up ~ o o ll o o o o ~ ~ ~ ~ ~ ~ ~ ~
~--~ - ~
O _ ~ ~ ~ ~ ~ ~r -1~ lo ~ W C~ O CO ~
QI ~ ~ CO Ct) 0;~ G~ CO G~
~ _ _______.
>~ ~ 0 ~ ~ ~ O ~r ~ ~; ~ t~ ~ ~ r k ~ ~'1 ~ r~l 1`'1 ~) t`') . .~ ~
\~ ~? O ' ~, ~3 ~ r~ ~ ~ r~ ~ ~7 ~r~ ~1 N ~ ~ I ~) ~ (~
~11 ''1._ ~;~ h , R; ~ ~ ~ ~ ~ ~ r U ; ~; r-l h ~ t~ ~ O
~: . . ~ _ ~ ~ ~ ~ r~ - rJo ~D O
l~ ~ ~ rl ~ 1 ~ . ~ .
~ ~ dP ~
. .. _ .
~: ~ . ~ ~
__ ~1 _ ~ ~ 5 X 3~
~ _ _ ,~ _ _ ~ r~
~ ~ }
_ ___ ~ ' ~
_ __. ______ . _ .
~;
X ~ O -. . ,. - _____.__________ __ _ .~ .
. . .
- .
.. . ' ~ ~ ' ' : ' ' , :.
Claims
PROPERTY OR PRIVILEGE IS CLAIMED AS DEFINED AS FOLLOWS:
1. Process for the manufacture of bis-benzoxazolyl-stilbene compounds of the formula I
(I) in which R1, R2 and R3, independent of one another, denote hydrogen, C1-C9 alkyl, carbo-C1-C4 alkoxy and trifluoromethyl, at least two of the radicals R1, R2 and R3 being hydrogen, by chlorination of an acid of the formula II
(IX) in which R1 is as defined under formula I, in an inert organic solvent and sub-sequent reaction with an aminophenol of the formula III
(III) in which R2 and R3 are as defined under formula I, which comprises adding the aminophenol in the form of a solution in an aprotic, dipolar solvent, preparing the compound of the formula IV
(IV) in which R1, R2 and R3 are as defined under formula I by acylation and preparingtherefrom the compound of the formula I by cyclization after addition of an acidcatalyst.
(I) in which R1, R2 and R3, independent of one another, denote hydrogen, C1-C9 alkyl, carbo-C1-C4 alkoxy and trifluoromethyl, at least two of the radicals R1, R2 and R3 being hydrogen, by chlorination of an acid of the formula II
(IX) in which R1 is as defined under formula I, in an inert organic solvent and sub-sequent reaction with an aminophenol of the formula III
(III) in which R2 and R3 are as defined under formula I, which comprises adding the aminophenol in the form of a solution in an aprotic, dipolar solvent, preparing the compound of the formula IV
(IV) in which R1, R2 and R3 are as defined under formula I by acylation and preparingtherefrom the compound of the formula I by cyclization after addition of an acidcatalyst.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000345572A CA1139764A (en) | 1980-02-13 | 1980-02-13 | Process for the manufacture of bis- benzoxazolyl-stilbene compounds |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000345572A CA1139764A (en) | 1980-02-13 | 1980-02-13 | Process for the manufacture of bis- benzoxazolyl-stilbene compounds |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1139764A true CA1139764A (en) | 1983-01-18 |
Family
ID=4116234
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000345572A Expired CA1139764A (en) | 1980-02-13 | 1980-02-13 | Process for the manufacture of bis- benzoxazolyl-stilbene compounds |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1139764A (en) |
-
1980
- 1980-02-13 CA CA000345572A patent/CA1139764A/en not_active Expired
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