BigPatents India

The present invention provides a process for the preparation of a compound of formula (I): wherein Rl is C1-6alkyl; R2 and R3 are, independently, C1-6 alkyl; and R4 is Cm alkyl or benzyl (wherein the phenyl ring of benzyl is optionally substituted by nitro, S (O)2(C1-4 alkyl), cyano, C1-4 alkyl, C1-4 alkoxy, C(O)(C1-4 alkyl). N(C1-6 alkyl)2 CF3 or OCF3,); the process comprising reacting a compound of formula (II): wherein R% R3 and R4 are as defined above, with a suitable base; and reacting the product so formed with RlOC(O)CH2X, wherein R1 is as defined above and X is chloro, bromo or iodo; wherein the process is carried out in a suitable solvent at a temperature in the range -40°C to -5°C; and wherein at least 0.2 moles of the compound of formula (II) are used in the process.