Intermediates, their process and use in preparation of selective α1-adrenoceptor antagonists, Silodosin

A process for preparing Silodosin and pharmaceutically acceptable salts thereof, wherein the process comprises the steps of:

• a) preparing compounds of Formula 1 or salts thereof wherein said process comprises the steps of:
• i) alkylation of compound of Formula 2 or salts thereof, with dihalogen alkane in aqueous medium to give compound of Formula 3 or salts thereof;
• wherein, n is an integer of 3;
• X is halogen;
• ii) VILSMEIER formylation of compound of Formula 3 or salts thereof to give compound of Formula 4 or salts thereof;
• wherein, n and X are as defined above, A is —CH;
• iii) condensation of compound of Formula 4 or salts thereof with nitroethane to give compound of Formula 5 or salts thereof;
• wherein, A(B) bond is double bond;
• R1 is Me;
• R2 is nitro and X, n are as defined above;
• iv) conversion of compound of Formula 5 or salts thereof to give compound of Formula 6 (6b and 6c) or salts thereof;
• 6b:
• R1, R2 absent, A(B) is single bond;
• B is COR, wherein, R is Me
• 6c:
• A(B) is single bond;
• R1 is Me and R2 is NO2
• wherein, X, n are as defined above;
• v) conversion of compound of Formula 6 or salts thereof to compound of Formula 1 or salts thereof in single or multiple steps;
• 1b:
• R1, R2 absent, A(B) is single bond, B is COR wherein, R is Me
• 1c:
• A(B) is single bond;
• R1 is Me and R2 is NO2
• wherein, R3 is selected from the group comprising of hydrogen, formyl, cyano, oxime, O-methyl oxime, O-acetyl oxime, O-propanoyl oxime, O-butanoyl oxime, and amide optionally substituted with aryl, C1-C4 alkyl or C1-C4 cycloalkyl;
• X and n are as defined above;
• b) halogen displacement of Compound of Formula I or salts thereof, to give compound of Formula 8 or salts thereof,
• 8b:
• R1, R2 absent, A is —CH2;
• B is COR, wherein, R is Me
• 8c:
• A(B) together are ethanyl group;
• R1 is Me and R2 is NO2
• wherein, P is hydroxyl protecting group and R3, X, n are as defined above;
• c) nitro reduction of compound of Formula 8c or salts thereof, to give compound of Formula 9 or salts thereof;
• wherein, R1 is Me and R2 is (un)substituted amine,
• wherein, P, R3, X, n are as defined above;
• and
• d) conversion of compound of Formula 8b and/or 9 or salts thereof to Silodosin and pharmaceutically acceptable salts thereof.