Hi,

 It depends on what heterocyclic system: For instance you can convert 2-aminopyridine to pyridone with NaNO2 + H2SO4:

Substituted 2-sulfonamido-5-aminopyridines. II

By Caldwell, Wm. T. et al

From Journal of the American Chemical Society, 66, 1479-84; 1944

Or, if the compound is a 4-aminotetrahydropyran, chromic acid will do the job.

Kinetics and mechanism of oxidation of 4-aminooxanes by chromium(VI)By Selvaraj, Kuppusamy et al

From Indian Journal of Chemistry, Section A:  Inorganic, Bio-inorganic, Physical, Theoretical & Analytical Chemistry, 32A(12), 1052-5; 1993

Be more specific. What heterocycle, and where is the NH2 attached?

Bill

Isopentyl nitrite functions as an organosoluble nitrosating agent that results in diazotisation under relatively neutral conditions, it has good precedent and is quite useful.

Add ~1.5 e.q. of isoamyl nitrite to your aromatic amine dissolved in 3:1 MeCN/H2O.

Start at 0 degrees or colder, heat if necessary, if yields are low try switching from N2 to air, adding a small quantity of H2O2, fiddling with the pH, or running the reaction in the absence of light.

It should work relatively well for aromatic heterocycles although procedures often require fine optimisation for good yields due to the potential for competing mechanistic pathways.

The reactions are often not particularly "clean". Side reactions include electrophilic nitrosation of electron rich systems, reductive deamination, azo coupling and dimerisation.

Dear Madhukar Baburao Deshmukh,

You can do the diazotization of the amino group using HCl and or/ AcOH with sodium nitrite (aq. excess, 3- 5 eqv.) and the subjecting this diazonium sol. to heating.

Good luck

Isopentyl nitrite good reagent for oxidation of amino group to keto group , but under unhydrous conditions.