GB893428A - Mercapto-tetrazaindene compounds and their use in photographic silver halide emulsions - Google Patents

Abstract

The invention comprises mercapto-substituted tetrazaindenes of the probable general formula <FORM:0893428/IV (b)/1> or salts thereof, wherein R1 represents an alkyl, aralkyl, acyl or haloacyl group, R2 represents hydrogen or an alkyl, aralkyl, acyl or haloacyl group or an alkylthio, aralkythio or arylthio group and R3 represents a hydrogen or halogen atom or an alkyl group, obtainable by replacement by an -SH group of the -OH group in the hydroxy-substituted tetrazaindene obtainable by the condensation of an acyl acetic ester R1COCHR3COOC2H5 with a 3-amino-1 : 2 : 4-triazole <FORM:0893428/IV (b)/2> wherein the Rs are as above defined, and also mercapto-substituted tetrazaindenes indenes of the general formula <FORM:0893428/IV (b)/3> or salts thereof, in which R1 and R2 have the above meanings and R4 represents an alkyl group when R1 is methyl and otherwise is hydrogen or an alkyl group. The two groups of mercapto-tetrazaindenes may be prepared from the corresponding hydroxy-substituted tetrazaindenes by reaction with P2S5 or from the corresponding chloro-substituted tetrazaindenes by reaction with an alkali metal hydrogen sulphide (e.g. KSH) or thiourea, preferably in methanol or other inert solvent. These chloro-substituted tetrazaindenes are obtained from the hydroxy analogues by reaction with phosphorus oxychloride and/or phosphorus pentachloride preferably in the presence of an organic tertiary base. The hydroxy-substituted tetrazaindenes used to prepare the second above-defined group of mercapto-tetrazaindenes are prepared by condensing an acyl acetic ester of the general formula R1COCHR4COOC2H5 with a 1-amino 1 : 3 : 4-triazole of the general formula <FORM:0893428/IV (b)/4> wherein R1, R2 and R4 are as above-defined. The first group of mercapto-tetrazaindenes wherein R3 is a halogen may also be prepared by condensation of an acyl acetic ester R1COCH2COOC2H5 with the above-defined 3-amino thiazoles, 5-halogenating the resulting hydroxyazaindene in solution or suspension with a halogen (e.g. chlorine or bromine), replacing the 4-OH group with chlorine by reaction with POCl3 and reacting the product with thiourea. The salts of the thiol products are preferably water-soluble, e.g. the sodium, potassium, ammonium and amine salts. Examples describe the preparation of the 6-methyltetrazaindene - 4 - thiol, 6 - phenyl - tetrazaindene - 4 - thiol, 5 - bromo - 6 - methyl - tetrazaindene - 4 - thiol, 2 : 6 - dimethyl - trtrazaindene - 4 - thiol, 6 - methyl - 2 - methylthio - tetrazaindene - 4 - thiol, 5 - ethyl - 6 - methyl - tetrazaindene - 4 - thiol and 5 - isobutyl - 6 - methyl - tetrazaindene - 4-thiol (all of the first-above formula) and 5-phenyl- and 6-ethyl-5-methyl-1 : 2 : 3a : 4-tetrazaindene-7-thiols. The compounds are photographic chemicals (see Group XX). Specification 619,557 is referred to.