If you mean Synodontis nyassae, they aren't often bred in aquariums. Synodontis are all egg scatterers, and only a few species have been successfully spawned in aquariums w/out hormone injections. Aside from getting adults properly conditioned, preventing them from eating the eggs seems to be the main difficulty. African rift lake species aeem to be easier to work with than the others, though aside from the multi's, lucipinnis, and petricola, I've only heard of one person successfully spawning S. granulosus.
You may find keeping mollies or other livebearers with the multi's helpful in encouraging them to spawn. The hormones from the livebearers should be as effective as the ones from cichlids. The multi's have been known to scatter eggs w/out hosts, but none were saved/hatched afterward.