Patent GB-851815-A (GB)
Title: Process for the preparation of 1:2:4-triazole-3-thiols
Inventor: KNOTT EDWARD BOWES
IPC: C07D513/04
Filed: 1956-06-04
Abstract: The invention comprises triazolo compounds of the general formula: <FORM:0851815/IV(b)/1> where Z1 represents a substituted vinylene group or an oxygen or sulphur atom or a -CR1 = N- group wherein R1 represents hydrogen or alkyl and R4 represents hydrogen or a substituent such as methyl, ethyl, chlorine, methoxyl, ethoxyl, hydroxy or amino and R represents hydrogen, alkyl such as methyl to butyl, or ammonium or alkali metal; and also 4-hydroxy-3-mercapto-6-methyl-1:2:3a:7-tetra azaindene, 6-hydroxy-3-mercapto-4-methyl-1:2:3a:7-tetrazaindene and three 11:21-dihydro quinolino-11:21-5:4-triazolo (1:2:4)-3-thiols substituted respectively by 61-chloro, 61-methyl and 41-methyl.  The invention also comprises methods for the preparation of these compounds in their thiol forms and of similar 1:2:4-triazolo-3-thiols having a fused ring system in the 4:5-positions.  In one method, a hydrazine of the general formula <FORM:0851815/IV(b)/2> wherein X represents a vinylene group, substituted or not, an oxygen atom, a sulphur atom or a -CR1 = N- group, wherein R1 represents hydrogen or alkyl, and Y and Z each represents hydrogen, hydroxyl or alkyl or Y and Z together represent the atoms necessary to complete a benzene ring which may contain substituents, with carbon disulphide and an organic amine, ammonia or an alkali metal hydroxide and heating the resulting b -substituted dithio carbazic acid salt to split-off H2S and produce the desired thiol; the product is treated with an acid to liberate the free thiol when an alkali metal hydroxide is used in the first stage.  The reaction of the hydrazines with CS2 and ammonia or an amine may be effected at room temperature; the second step may be effected at 50 DEG C. or higher.  The hydrazines may be heated with CS2 and an alkali metal hydroxide to give salts of the desired thiols in one stage.  A preferred process comprises heating to split-off hydrogen sulphide therefrom a compound of the general formula <FORM:0851815/IV(b)/3> wherein X, Y and Z are as above defined and R1 represents hydrogen, alkyl, hydroxyalkyl or phenyl and R2 and R3 each represent hydrogen, alkyl or hydroxyalkyl or R1 and R2 together represent the non-metallic atoms necessary to complete a heterocyclic ring and R3 represents alkyl or a second bond joining R2 to N.  The amines utilisable as such or in the form of their dithio carbazic acid salts include pyridine, quinoline, triethylamine, triethanolamine, tripropylamine, N-methyl piperidine and dialkyl anilines.  The thiol products may be alkylated at the -SH group by reaction with an alkyl ester such as methyl or ethyl iodide and an alkali.  The alkali metal salts of the thiol compounds may be converted into other metal salts by treatment with an aqueous solution of an inorganic metal salt such as silver nitrate.  The triazole-thiols may be used in photographic emulsions as described in Specification 851,816.  In Examples: (1) 21:31-dihydrobenzothiazolo-31:214:5 -triazole (1:2:4-)3-thiol is prepared by reacting CS2 with 2-benzothiazolyl hydrazine in pyridine, then heating in a steam bath until evolution of H2S ceases, pouring the product into water, purifying the precipitate with charcoal in boiling Na2CO3 solution and acidifying to liberate the desired thiol; in similar manner there are prepared, (2) 11:1-2dihydroquinolino-11:41:4:5-triazole (1:2:4)-3-thiol from 2-quinolyl hydrazine, (3) 21:31-dihydro benzoxazolo-31:21:4:5-triazole (1:2:4)-3-thiol from 2-benzoxazolylhydrazine, (5) 11:21-dihydro-61-chloroquinolino -11:21-5:4-triazole (1:2:4)-3-thiol from 6-chloro-2-hydrazino quinoline, (6) 21-dihydro-61-methyl quinolino-11:21-5:4-triazole(1:2:4)-3-thiol from 2-hydrazino-6-methyl quinoline and (7) 11:21-dihydro-41-methyl quinolino-11:21-5:4-triazole (1:2:4)-3-thiol from 2-hydrazino-4-methyl quinoline.  In Example (4) 2-hydrazino-4-hydroxy-6-methyl pyridine in aqueous NaOH-pyridine is reacted with CS2 and heated on a steam bath and the product is poured into water and acidified yielding a mixture of 4-hydroxy-3-mercapto-6-methyl-1:2-3a:7-tetraza indene and the corresponding 6-hydroxy-4-methyl isomer, the latter being separated from the mixture by extraction with boiling water.  The hydrazine used in (5) is prepared by refluxing 2:6-dichloro quinoline with excess hydrazine hydrates.  The dithio carbazic acids, used above in salt form, may be prepared by reacting the appropate hydrazine with CS2.