Process for the preparation of gabalactam

An improved process for the preparation of gabalactam of the formula 1

• Which comprises
• (i) Preparing an aqueous solution of an alkali or alkaline earth hydroxide in a concentration ranging from 10 to 20% by weight, adding bromine to the resulting solution to give the appropriate alkali or alkaline earth hypobromite solution having a concentration ranging from 5 to 10% by weight,
• (ii) adding 1 part by weight of an amide of the formula 4
• to 7.5 to 9.5 parts by weight, of the solution of the alkali/alkaline earth hypobromite obtained in step (i) during a period in the range of 1-4 hours, at a temperature in the range of −10 to +10 degrees C.,
• (iii) Keeping the resultant mixture for ageing in the temperature in the range of −10 to +10 degree C. for a period in the range of 0.5 to 2 hours,
• (iv) Heating the mixture gradually to a temperature in the range of 80 to 100 degrees C., for a period in the range of 3 to 8 hours,
• (v) Cooling the reaction mixture to a temperature in the range of 30 to 50 degrees C.,
• (vi) Extracting the mixture using a nonpolar solvent or a mixture thereof,
• (vii) subjecting the resulting organic layer washed aqueous layer to the steps of (iii) to (v) defined above
• (viii) Combining the organic layers obtained in steps ((vi) & (vii) together
• (ix) washing resulting combined organic layers with water at a temperature in the range of 30-35 and
• (x) Distilling of the organic solvent at a temperature in the range of 60-110 deg C., under reduced pressure.