I am trying to synthesize imine bases of a heterocyclic compound containing both N and S in its cyclic structure, and an amino group is attached to the C between the S and N using various benzaldehydes. Even after refluxing for 5-6 hours i am getting solid product which immediately gets liquified on filteration. Whereas when i reflux for 2-3 hours i am not getting any solid product at all. Can you please suggest any modifications or the reason of why i am not getting the product?