Synthesis of 2-Amino-4,6-diarylnicotinonitriles Using Silica-Bound N-Propyl Triethylenetetramine Sulfamic Acid as a Recyclable Solid Acid Catalyst

A simple and efficient procedure for the preparation of silica-bound N-propyl triethylenetetramine sulfamic acid (SBPTETSA) by the reaction of silica-bound N-propyl triethylenetetramine (SBPTET) with chlorosulfonic acid in chloroform is described. Silica-bound N-propyl triethylenetetramine sulfamic acid was employed as a recyclable catalyst for the synthesis of 2-amino-4,6-diarylnicotinonitriles from the multi-component reaction of an acetophenone derivative, an aromatic aldehyde, malononitrile, and ammonium acetate under solvent-free conditions at 100 degrees C. The heterogeneous catalyst was recycled for five consecutive runs in the optimized multi-component reaction of 4-chloroacetophenone, 4-chloroenzaldehyde, malononitrile, and ammonium acetate without significant loses to its catalytic activity.