Beta-diketo compounds and related N-heterocycles have played a significant role in synthetic organic chemistry. A multistep mechanism for a catalyze base reaction of 1,3-indandione 1 with acetone has been developed to afford a complex molecule, 3-(1,3-Dioxo-2-indanylidene)-1,1-dimethyl-1,2,3,4,4d, 9a-hexahydrofluorene 2. Pharmacologically active compounds 3, with anticoagulant and antispasmodic properties, have been synthesized through the reaction of 2-substituted 1,3-indandione with β-chloro-vinyl ketones. Interaction of phthalimide 4 with benzyl chloride in DMF in presence of K2CO3-Al2O3 leads to the formation of N-benzyl phthalimide 11.N-substituted products of type 15 and 16 have been obtained when 6-alkyl or aryl -4(aryl methyl) pyridazine-3(2H)-ones 14 interacted with Bromo-ethyl acetate and acetic-anhydride respectively. However, 3-chloro substituted pyridazines 17 afforded 3-mercaptopyridazine derivatives 18 when interacted with thiourea.In this paper, we suggest multistep mechanisms for a series of compounds and all the proposed mechanisms are unknown.