Exemestane and their intermediates and methods of preparation thereof

Method of preparing a compound of formula (I) wherein each of R1, R2, R3, R4, independently, is hydrogen, halogen or C1-C6 alkyl, the method comprising: reacting a compound of formula (II) wherein R1, R2, R3, R4 are as defined above and R is methylene with a deprotonating agent and a compound of formula R5SO2X wherein R5 is C1-C5 and X is halogen so obtained a compound of formula (III) wherein R1, R2, R3, R4, R5 are as defined above; and reacting the compound of formula (III) with a base.