We claim:
1. A process for the preparation of Primidone (1) having purity greater than 99.0% comprising: a) reacting diethyl 2-ethyl-2-phenylmalonate (5)
with thiourea (4) and base to form sodium 5-ethyl-4,6-dioxo-5-phenyl-1,4,5,6-tetrahydropyrimidine~2-thiolate (3);
b) acidifying sodium 5-ethyl-4,6-dioxo-5-phenyl-l,4,5,6-tetrahydro pyrimidine-2-thiolate (3) with suitable acid to form 5-ethyl-5-phenyl-2-thioxodihydropyrimidine-4,6(lH,5H)-dione (2);
c) reducing 5-ethyl-5-phenyl-2-thioxodihydropyrimidine-4,6(lH,5H)-dione
using suitable reducing agent to form Primidone (1).
2. The process according to claim 1, where in the base used in step a) sodium
hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate,
potassium carbonate, potassium bicarbonate, lithium hydroxide, aqueous
ammonia

3. The process according to claim 1, where in the acid used in step b)is selected from hydrochloric acid, hydrobromic acid, sulphuric acid, phosphoric acid.
4. The process according to claim 1, where in the reducing agent c) is selected from hydrogen, cobalt, nickel, lithium, zinc, iron.
5. The process as claimed in claim 1, wherein the suitable solvent is selected from water, methanol, ethanol, isopropyl alcohol (IPA), n-propanol, n-butanol, acetone, dichloromethane, tetrahydrofuran, ethyl acetate, acetonitrile, dimethyl formamide and dimethyl sulfoxide
6. Process for the purification of Primidone (1), which comprises of:
i. providing a solution of Primidone (1) in a suitable solvent;
ii. heating the reaction mixture to a suitable temperature; iii. cooling the reaction mixture to suitable temperature; iv. isolating the pure Primidone (1)
7. The process as claimed in claim 6, wherein the suitable solvents used is selected
from a group comprising of acetone, dichloromethane, toluene, ethyl acetate,
methanol, ethanol, isopropyl alcohol (IPA), n-propanol, n-butanol, water or
mixtures thereof.
8. The process, as claimed in claim 6, wherein the Primidone (1) obtained after
purification is having purity greater than 99.0 (%, w/w) purity by HPLC.