Abstract: A process is provided for the production of compounds having the formula: ##STR1## in which R is hydrogen, C.sub.1 -C.sub.5 alkyl, cyano or halogen; M is hydrogen or a salt-forming colorless cation; and n is 2;which process comprises reductively de-aminating a compound having the formula: ##STR2## in which R and n have their previous significance and M' is hydrogen, a salt-forming colorless cation or optionally substituted phenyl; and converting any optionally substituted phenyl group M' to a group M.The present invention also provides processes for the production of the compounds of formula (2) and various novel intermediates for use in the new processes.The compounds of formula (1) are useful as fluorescent whitening agents.