The original Schiff' s experimental conditions tolerate a lot of substituents in the main structures of the reagents.
The references are:
Schiff, Hugo (1866). "Eine neue Reihe organischer Diamine" Annalen der Chemie und Pharmacie, Supplementband. 3: 343–370.
Schiff, Hugo (1866). "Eine neue Reihe organischer Diamine. Zweite Abtheilung" Annalen der Chemie und Pharmacie. 140: 92–137. doi:10.1002/jlac.18661400106.
You can also Try Solvent free synthesis by microwave irradiation
The microwave assisted syntheses of Schiff bases from different aldehyde and amines is carried out efficiently and high yield of product in short time has been obtained