TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: The imatinib or imatinib mesylate preparation process comprises: either (a1) condensing (III) with (IV) in the presence of a solvent and pyridine to obtain reaction mass, (b1) adding concentrated hydrochloric acid to adjust the pH of reaction mixture to 2-3, (c1) separating the aqueous layer and adding sodium nitrite, (d1) isolating the pure imatinib which is substantially free of genotoxic impurity (III), and (e1) optionally converted into imatinib mesylate salt; or (a2) suspending imatinib free base in water, (b2) cooling the reaction mixture and adding concentrated hydrochloric acid to adjust the pH of reaction mixture to 2-3, (c2) adding sodium nitrite to the above solution, and (d2) isolating pure imatinib which is substantially free of genotoxic impurity (III). Preferred Components: The solvent used in step (a) is esters comprising ethyl acetate or isopropyl acetate, chlorinated solvents comprising chloroform or dichloromethane, nitriles comprising acetonitrile, ketones comprising acetone or methyl ethyl ketone, and/or ether comprising diethyl ether, 1,4-dioxane, diisopropyl ether, methyl tert-butyl ether or tetrahydrofuran. The solvent used in step (b) or (a1) is chlorinated solvents comprising chloroform or dichloromethane, hydrocarbons comprising toluene, xylene or chlorobenzene, ethers comprising diethyl ether, 1,4-dioxane, diisopropyl ether, methyl tert-butyl ether or tetrahydrofuran, and/or aprotic polar solvents comprising dimethylformamide, dimethyl sulfoxide or dimethylacetamide. The amount of pyridine used for condensing (III) with (IV) is 0.4-6 (preferably 0.5-2) molar equivalent of (IV). The solvent used in step (c) is chlorinated solvents comprising chloroform or dichloromethane, and/or aprotic polar solvents comprising dimethylformamide, dimethyl sulfoxide or dimethylacetamide. The solvent used in step (d) is esters comprising ethyl acetate or isopropyl acetate, ketones comprising acetone or methyl ethyl ketone, and/or alcohols comprising methanol, ethanol, isopropyl alcohol, 1-butanol, 2-butanol, tert-butanol. The solvent-A is esters comprising ethyl acetate or isopropyl acetate, chlorinated solvents comprising chloroform or dichloromethane, nitriles comprising acetonitrile, hydrocarbons comprising toluene, xylene or chlorobenzene, ketones comprising acetone or methyl ethyl ketone, ethers comprising diethyl ether, 1,4-dioxane, diisopropyl ether, methyl tert-butyl ether or tetrahydrofuran, and/or aprotic polar solvents comprising dimethylformamide, dimethyl sulfoxide or dimethylacetamide. The crystalline form of imatinib base further has a powder X-ray diffraction (PXRD) pattern, as given in the specification. ACTIVITY - Cytostatic.    MECHANISM OF ACTION - None given.    EXAMPLE - 6 g of N-(5-Amino-2-methylphenl)-4-(3-pyridyl)-2-pyrimidine-amine and 60 ml of dichloromethane were charged in a vessel at room temperature in the presence of nitrogen atmosphere. Further 8.8 g of 4-((4-methylpiperazin-1-yl) methyl)benzoyl chloride dihydrochloride and 60 ml of dichloromethane was added into the reaction mixture and stirred for 30 minutes at room temperature (25-35 degrees C). Subsequently, 2.7 ml of pyridine was added and the reaction mixture was stirred for 3 hours. After reaction completion, 30 ml of water followed by concentrated hydrochloric acid was added to reaction mixture to attain pH of 2-3. The reaction mixture was stirred for 30 minutes. The aqueous layer was separated and 30 mg of sodium nitrite was added and stirred for 30 minutes. Further 60 ml of dichloromethane and 18 ml of methanol were added into the reaction mixture and stirred for 30 minutes. Reaction mixture pH was adjusted by 20% sodium carbonate solution and worked up to give imatinib free base.