Cyan dye-forming couplers and photographic materials containing same

A photographic element comprising a support and a photosensitive silver halide emulsion which has associated therewith a cyan dye-forming coupler compound having the structural formula:

• ##STR47## wherein:
• R.sup.1 is an unsubstituted or substituted, straight or branched chain alkyl group having from 1 to about 20 carbon atoms, an unsubstituted or substituted cycloalkyl group having from 3 to about 8 carbon atoms in the ring, an alkylcarbonyl or an alkoxycarbonyl group having from 1 to about 20 carbon atoms in the alkyl or alkoxy moiety;
• R.sup.2 is defined for R.sup.1 or is hydrogen;
• R.sup.3 is an unsubstituted or substituted alkyl group having from 1 to about 24 carbon atoms, an unsubstituted or substituted cycloalkyl group having from 3 to about 8 carbon atoms in the ring, an unsubstituted or subsituted aryl group having from 6 to about 24 carbon atoms, or an unsubstituted or substituted heterocyclic group having from 3 to about 8 atoms in the heterocyclic ring wherein the hetero ring atoms can be nitrogen, oxygen, or sulfur;
• with the proviso that when R.sup.3 is a primary alkyl group R.sup.1 must contain at least 2 carbon atoms;
• and
• Z is hydrogen or a coupling off group.