Photochemical Reactions of Azo Compounds. II. Photochemical Cyclodehydrogenations of Methyl- and Dimethylazobenzenes

1963 ◽  
Vol 16 (6) ◽  
pp. 1042 ◽  
Author(s):  
GM Badger ◽  
RJ Drewer ◽  
GE Lewis
Keyword(s):  
Sulphuric Acid ◽  
Photochemical Reactions ◽  
Azo Compounds ◽  
Methyl Substituent

Substituted benzo[c]cinnolines have been prepared from substituted azobenzenes by photochemical cyclodehydrogenation in 22N sulphuric acid. The reaction seems to involve a photochemical disproportionation as rearrangement products of the corresponding hydrazobenzenes were also formed. 4-Methylazobenzene gave 2-methylbenzo[c]cinnoline. 3-Methylazobenzene gave a mixture of 1- and 3-methylbenzo[c]cinnolines: and 2-methylazobenzene gave 4-methylbenzo[c]cinnoline and benzo[c]cinnoline. The latter result is noteworthy as it indicates that cyclization can proceed with elimination of a methyl substituent. Similar elimination was observed with 2,2'-dimethylazobenzene, which gave 4-methyl-benzo[c]cinnoline as well as the expected 4,7-dimethylbenzo[c]cinnoline. Photochemical cyclodehydrogenations of 4,4'-dimethylazobenzene and of 3,3'-dimethyl-azobenzene have also been studied.

Photochemical reactions of azo compounds. III. Photochemical cyclodehydrogenations of substituted azobenzenes

1964 ◽  
Vol 17 (9) ◽  
pp. 1036 ◽  
Author(s):  
GM Badger ◽  
RJ Drewer ◽  
GE Lewis
Keyword(s):  
Carboxylic Acid ◽  
Sulphuric Acid ◽  
Photochemical Reactions ◽  
Azo Compounds ◽  
Methyl Substituent ◽  
Acid Lactone

2,4,6-Trimethylazobenzene has been shown to undergo photochemical cyclodehydrogenation in sulphuric acid to give 2,4-dimethylbenzo[c]cinnoline and 1,2,4-trimethylbenzo[c]cinnoline. The formation of the former involves cyclization with the loss of a methyl substituent : the formation of the latter involves cyclization with the migration of a methyl substituent. The reaction involves a photochemical disproportionation: 4-(4-aminophenyl)-2,4,6-trimethylcyclohexa-2,5-dienone was also isolated, having been formed by acid-catalysed rearrangement (and hydrolysis) from 2,4,6-trimethylhydrazobenzene. Substituted azobenzenes having a carboxy, iodo, or chloro substituent in the 4-, 3-, or 2-position have also been irradiated and the resulting benzo[c]cinnolines and benzidines isolated and characterized. Irradiation of 2-substituted azobenzenes has been found to give the parent benzo[c]cinnoline as well as the 4-substituted benzo[c]-cinnoline, showing that carboxy-, iodo-, and chloro-substituents can be ejected as well as methyl substituents. The irradiation of azobenzene-3-carboxylic acid has given 1-hydroxybenzo[c]cinnoline-10-carboxylic acid lactone in addition to benzo[c]-cinnoline-3-carboxylic acid.

Photochemical reactions of azo compounds. IX. Further studies related to the photochemical reactions of bisazo compounds

1967 ◽  
Vol 20 (2) ◽  
pp. 321 ◽  
Author(s):  
NC Jamieson ◽  
GE Lewis
Keyword(s):  
Sulphuric Acid ◽  
Photochemical Reaction ◽  
Photochemical Reactions ◽  
Azo Compounds ◽  
Bisazo Compounds ◽  
First Time

The photochemical reactions of 4,4?-bis(phenylazo)biphenyl and 4- phenyl-azoazobenzene in 98% sulphuric acid have been examined, for comparison with the corresponding reactions in 22N acid. Photochemical cyclodehydrogenation of 4-phenylazoazobenzene to two benzo[c]cinnoline derivatives has thereby been effected for the first time. The observed course of the latter reaction has led, in turn, to studies of the benzidine rearrangement of 2-(2-phenylhydrazino)benzo[c]- cinnoline, of the photochemical cyclodehydrogenation of 3-phenylazobenzene, and of the photochemical reaction of 2-phenylazobenzo[c]cinnoline. The results of these investigations are now recorded and discussed.

Photochemical reactions of azo compounds. XIII. Photochemical reaction of 11H-Dibenzo[c,f]-[1,2]-diazepine under acidic conditions

1967 ◽  
Vol 20 (10) ◽  
pp. 2229 ◽  
Author(s):  
CP Joshua ◽  
GE Lewis
Keyword(s):  
Sulphuric Acid ◽  
Acid Derivative ◽  
Photochemical Reaction ◽  
Photochemical Reactions ◽  
Sulphonic Acid ◽  
Azo Compounds ◽  
Acidic Conditions

11H-Dibenzo[c,f]-[1,2]-diazepine is converted into a mixture of dibenzo[c,f]-[1,2]-diazepin-11-one, 2,2?-diaminobenzophenone, and 2,2?- diaminodiphenylmethane when irradiated in weakly acidic ethanol. Irradiation of the same compound in concentrated sulphuric acid appears to give only a sulphonic acid derivative of diaminobenzophenone. No photochemical reaction occurs in neutral ethanol or in benzene.

Photochemical reactions of azo compounds. VII. Studies of the photochemical reactions of azobenzene under various acidic conditions

1966 ◽  
Vol 19 (8) ◽  
pp. 1445 ◽  
Author(s):  
GE Lewis ◽  
RJ Mayfield
Keyword(s):  
Acetic Acid ◽  
Acetic Anhydride ◽  
Sulphuric Acid ◽  
Photochemical Reaction ◽  
Acetyl Chloride ◽  
Photochemical Reactions ◽  
Aluminium Chloride ◽  
Azo Compounds ◽  
High Yield ◽  
Acidic Conditions

An investigation has been made of the photochemical and dark reactions of azobenzene in acetic acid-ferric chloride and acetic acid-aluminium chloride mixtures for comparison with the corresponding reactions of azobenzene in sulphuric acid. The photochemical reactions resulted in cyclodehydrogenation of azobenzene to benzo[c]cinnoline, and small quantities of reduction products of azobenzene were also isolated. The formation of reduction products was again observed in the dark reactions, but there was no sign of cyclodehydrogenation. The significance of these observations is now discussed. Irradiation of azobenzene in acetyl chloride, or in acetic anhydride containing hydrogen chloride, resulted in a novel photochemical reaction in which NN?-diacetyl-4-chlorohydrazobenzene was formed in high yield.

Photochemical reactions of azo compounds. V. Photochemical cyclodehydrogenations of Amino-, Acetyl-, and Nitro-azobenzenes

1965 ◽  
Vol 18 (10) ◽  
pp. 1639 ◽  
Author(s):  
GM Badger ◽  
CP Joshua ◽  
GE Lewis
Keyword(s):  
Sulphuric Acid ◽  
Photochemical Reactions ◽  
Azo Compounds

4-Benzdaminoazobenzene and 4,4'-bisbenzalaminoazobenzene have been shown to undergo photochemical cyclodehydrogenation in concentrated (98%) sulphuric acid to give 2-aminobenzo[c]cinnoline and 2,9-diaminobenzo[c]cinnoline respectively in excellent yields; but 4-aminoazobenzene and 4,4'-diaminoazobenzene were not cyclized. 3-Arninoazobenzene and 3-benzalaminoazobenzene both gave 3-aminobenzo[c]cinnoline. 3-Nitro- and 3-acetyl-azobenzenes gave 3-nitro- and 3-acetyl-benzo[c]cinnolines; and 4-nitro- and 4-acetyl-azobenzenes gave 2-nitro- and 2-acetyl-benzo[c]cinnolines.

Photochemical reactions of azo compounds. IV. Further photochemical cyclodehydrogenations

1965 ◽  
Vol 18 (2) ◽  
pp. 190 ◽  
Author(s):  
GM Badger ◽  
NC Jamieson ◽  
GE Lewis
Keyword(s):  
Sulphuric Acid ◽  
Photochemical Reactions ◽  
Azo Compounds ◽  
Simultaneous Reduction ◽  
Reduction And Oxidation

1,1'-, 1,2'-, 2,2'-Azonaphthalenes, and 2-phenylazonaphthalene are not cyclized photochemically under conditions in which azobenzene is converted into benzo[c]cinnoline and benzidine; but 1-phenylazonaphthalene has been shown to give naphtho[1,2-c]cinnoline, and 4-phenylazobenzene gave 2-phenylbenzo[c]cinnoline. Although 4-styrylazobenzene showed some evidence of cyclization, the reaction was extremely slow and was accompanied by considerable decomposition. 4-Phenylezoazobenzene was cleaved by sulphuric acid, and no cyclized product was obtained. Irradiation of 4,4'-bis(phenylazo)biphenyl gave two cleavage products, and two benzo[c]cinnoline derivatives. Simultaneous reduction and oxidation apparently occurred within the same molecule.

Photochemical reactions of azo compounds. XI. Formation and characterization of 2-Dimethylaminobenzo[c]cinnoline

1967 ◽  
Vol 20 (7) ◽  
pp. 1451 ◽  
Author(s):  
GE Lewis ◽  
JA Reiss
Keyword(s):  
Sulphuric Acid ◽  
Good Yield ◽  
Photochemical Reactions ◽  
Azo Compounds

2-Dimethylaminobenzo[c]cinnoline is formed when 4-dimethylaminoazo benzene N-oxide is irradiated in 22N sulphuric acid. The same product arises in good yield when 2-chlorobenzo[c]cinnoline is heated with dimethylamine in a sealed tube at 160-170�. A compound formerly described in the literature as 2-dimethyl-aminobenzo[c]cinnoline has now been shown to be 4,4?-bis(4-dimethylaminophenylazo)biphenyl.

Photochemical reactions of azo compounds. X. Photochemical properties of azobenzene-2-carboxylic acids

1967 ◽  
Vol 20 (5) ◽  
pp. 929 ◽  
Author(s):  
CP Joshua ◽  
GE Lewis
Keyword(s):  
Hydrogen Bonding ◽  
Carboxylic Acid ◽  
Carboxylic Acids ◽  
Intramolecular Hydrogen Bonding ◽  
Photochemical Reactions ◽  
Azo Compounds ◽  
Neutral Compounds ◽  
Methyl Derivatives ◽  
Intramolecular Hydrogen ◽  
Derivatives Of

Two chloro and two methyl derivatives of azobenzene-2-carboxylic acid have been found to yield the corresponding derivatives of benzo[c]cinnoline-4- carboxylic acid in good yields when irradiated in 98% sulphuric acid. The question of intramolecular hydrogen bonding in relation to the properties of azobenzene-2-carboxylic acids is discussed. Infrared absorption spectra of the neutral compounds have provided confirmation of internal hydrogen bonding. Attempts to prepare the cis isomers of these azo compounds have been unsuccessful.

Photochemical reactions of azo compounds. XII. Dark reaction of cis-azobenzene with acetyl chloride

1967 ◽  
Vol 20 (9) ◽  
pp. 1899 ◽  
Author(s):  
GE Lewis ◽  
RJ Mayfield
Keyword(s):  
Trans Isomer ◽  
Potassium Hydroxide ◽  
Acetyl Chloride ◽  
Photochemical Reactions ◽  
Azo Compounds ◽  
Dark Reaction ◽  
Purple Coloration ◽  
Dark Blue ◽  
Induced Reaction ◽  
Trans Azobenzene

cis-Azobenzene has been shown to react with acetyl chloride in the absence of light to form N,N?-diacetyl-4-chlorohydrazobenzene and N?- acetyl-4-chloro-hydrazobenzene as the principal products; 4- phenylaminoazobenzene and acetanilide are also formed in small amounts. In the course of the reaction a metastable dark blue product arises, and, although this could not be satisfactorily characterized, it was found to yield 4-phenylaminoazobenzene on decomposition in methanolic potassium hydroxide or in acetyl chloride. The intense blue-purple coloration, which occurs as soon as the reactants are mixed, enables cis-azobenzene to be readily distinguished from its trans isomer. The nature of the currently reported reaction is discussed in relation to the previously reported photo-induced reaction of trans- azobenzene with acetyl chloride, which yields N,N?-diacetyl-4- chlorohydrazobenzene practically exclusively.

Photochemical reactions of azo compounds. XVI. Reactions with acetyl chloride leading to Di-, Tri-, and Tetra-chloroazobenzenes

1968 ◽  
Vol 21 (6) ◽  
pp. 1601 ◽  
Author(s):  
GE Lewis ◽  
RJ Mayfield
Keyword(s):  
Acetyl Chloride ◽  
Photochemical Reactions ◽  
Azo Compounds

A previously reported method for converting azobenzene into 4-chloroazobenzene (via N,N'-diacetyl-4-chlorohydrazobenzene) has been extended to the preparation of di-, tri-, and tetra-chloroazobenzenes.

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