As particularly preferred examples of R1 --CO--which is found in the formulas 1!, 4c!, 5c! to 5f!, etc., there may be mentioned groups of the following formulas: ##STR1## where R4 and R5 may be the same or different and each is a hydrogen atom, a lower alkyl, lower alkoxyl, nitro or amino group; ##STR2## where R6 is a hydrogen or halogen atom or a lower alkyl or halo-lower alkyl group, R7 is a hyd