Process for the preparation of 2-acetyl-1-pyrroline, the basmati rice flavorant

An improved process for the preparation of 2-acetyl-1-pyrroline, the said process comprising steps of:

• a) dissolving L-proline in dry alcohol, cooling to a temperature in the range of −5° C. to −15° C.,
• b) adding thionylchloride to step (a) solution, maintaining the temperature of reactant mixture below 0° C.,
• c) stirring the reactant mixture of step (b) at a temperature range of 20° to 30° C. for a time period of 1 h to 4 h,
• d) removing the solvent from reactant mixture of step (c) to obtain a residue, which is stored in ice-chest for a time period of 10 h to 16 h to obtain a solid mass,
• e) adding the solid mass of step (d) to 50% aqueous alkali carbonate solution, extracting with an organic solvent, separating the organic and aqueous layer,
• f) drying the organic layer of step (e) over anhydrous sodium sulphate, filtering, evaporating the solvent from filtrate to obtain a residue,
• g) distilling the residue of step (f) to obtain 2-carbomethoxy-1-pyrrolidine,
• h) dissolving 2-carbomethoxy-1-pyrrolidine of step (g) in ether, cooling to a temperature range of 0° to 5° C., adding drop wise t-butylhypochlorite over a period of 10 minutes to 30 minutes, stirring at a temperature range of 20° to 30° C. for a time period of 4 h to 6 h,
• i) filtering the solution of step (h), removing the solvent from the filtrate to obtain 2-carbomethoxy-1-pyrroline,
• j) preparing Grignard Reagent in dry ether by adding magnesium turning, iodine followed by dropwise methyl iodide and stirring at a temperature in the range of 25° C. to 35° C. for completion of reaction, cooling the mixture to 0° C.,
• k) adding an ethereal solution of 2-carbomethyoxy-1-pyrroline to the cooled mixture of step (j), stirring at a room temperature till the reaction is complete,
• k) adding 5% aqueous hydrochloric acid to step (k) mixture, extracting with diethyl ether, separating the organic layer, drying the organic layer over anhydrous sodium sulphate, filtering to obtain a filtrate, and
• l) distilling the filtrate of step (i) to obtain pure 2-acetyl-1-pyrroline.