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Part-IResults and Discussion3.4 Mild Oxidation of Thio Derivatives (IIIi-xxxv) to Sulfinyl Derivatives Using m-Chloroper-Benzoic Acid (m-CPBA) (IVi-xxxv)The organic sulfides may be selectively oxidized to sulfinyl derivatives by using m-CPBA 28.Since oxidation using per acids occurs under very mild conditions, it can be successfullyapplied to the preparation of base sensitive sulfoxides. 39-41 Oxidation of sulfides with 1.2moles of m-CPBA in methanol & dichloromethane at 0 o C gave the corresponding sulfinylderivative in quantitative yields. Further, the reaction doesn’t proceed further to the sulfonylsunder these reactions conditions using this reagent.Thus, the target 2-(1H-benzimidazol-2-yl)methylsulfinylcondensedpyrimidin-4(3H)-ones and2-{[(5-methoxy-1H-benzimidazol-2-yl)methylsulfinylcondensedpyrimidin-4(3H)-ones (IVixxxv)were synthesized by mild oxidation of 2-(1H-benzimidazol-2-yl) and 2-{[(5-methoxy-1H-benzimidazol-2-yl)methylthiocondensedpyrimidin-4(3H)-ones (IIIi-xxxv) using m-chloroperbenzoic acid as oxidizing agent (Scheme-21).ONHNIIIi-xxxvSHNNYOMild OxidationY = H, OCH 3NHONSNIVi-xxxvScheme-21HNYThe proposed reaction of oxidation involves a nucleophilic attack by the sulfide on acyclic hydrogen-bonded form of the peracid 42-43 (Scheme-22).92