Tungstate Sulfuric Acid (TSA) /NaNO2as a Novel Heterogeneous System for the N-Nitrosation of Secondary Amines under Mild Conditions

Nitrosation chemistry has been introduced as an active area for organic and biological chemists. Their strong mutagenic and carcinogenic properties of N-nitrosamines have caused considerable attraction in this view. Also they have been used as pesticides, lubricant and antioxidants. NNitrosamines have key role in preparation of various N, Nbonded functionalities and their easy lithiation followed by denitrosative electrophilic reaction which can be applied for the electrophilic substitution of secondary amines at the aposition. In situ generated HNO2 from sodium nitrite and inorganic acids in water or water/alcohol mixture solvent, is the most general reagent for nitrosation. Some other nitrosating agents, such as fermy's salt, N-haloamides/ NaNO2 under phase-transfer conditions, 5 nitrogen tetroxide, oxyhyponitrite and oxalic acide have been reported. Recently, several heterogeneous reagent systems using Nafion-H, silica sulfuric acid and trichloroisocyanuric acid in combination with NaNO2 have also been used. Today, heterogenation of chemical systems is an active field in industrial and laboratorial chemistry because of simplification in handling procedures, reduction of corrosion, green chemistry point of view, avoidance of byproducts, easy and clean reaction and simple work-up. With regard to wide application of acids as reagent or catalyst in organic chemistry, (for producing more than 1 × 10 mt/year of products) introduction of a new inorganic solid acid can be useful in this direction. Recently silica sulfuric acid and Nafion-H have been used for a wide variety of reactions such as production of disulfides from thiols, oxidation of 1,4-dihydropyridines, N-nitrosation of secondary amines,