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Reagents and reaction conditions: (i) Ammonium thiocyanate, gla. CH3COOH, reflux 3–4 h, (ii) Chlorosulfonic acid, 1,4 dioxane, stirring at r.t., (iii) Pyridine, aniline (3a), p-nitro aniline (3b), 2-amino pyridine (3c), reflux 3–4 h, (iv) Ethyl chloroformate, anhydrous K2CO3, dry acetone, reflux 18–20 h, (v) Substituted primary aromatic amines (R′NH2), toluene, reflux 3–4 h.
