Preparation method of silodosin key intermediate

The invention discloses a preparation method of a silodosin key intermediate, and belongs to the technical field of medicine synthesis. Carrying out Friedel-Crafts reaction on indoline and trichloroacetonitrile to obtain a compound 1; brominating to obtain a compound 2; then carrying out substitution with 2-(3-bromopropoxy) tetrahydro-2H-pyran to obtain a compound 3; then carrying out nucleophilic addition with (S)-epoxypropane or (R)-epoxypropane at an ultralow temperature to obtain a compound 4; then carrying out Mitsunobu reaction with phthalimide to obtain a compound 5 (configuration inversion) or esterifying with paratoluensulfonyl chloride, and reacting with potassium phthalimide under the condition of inorganic alkali to obtain the compound 5; reducing through hydrazine hydrate to obtain a compound 6; then removing tetrahydropyran protection from p-toluenesulfonic acid to obtain a compound 7; performing amino Boc protection under an alkaline condition to obtain a compound 8; esterifying with benzoyl ch