General procedure for the synthesis of 5-amino-2,3,3-trimethyl-3H-indole (product B) from 5-nitro-2,3,3-trimethylindole (product A):
Example of implementation:
A mixture of 6.6 g of Product A, 43.7 g of stannous chloride dihydrate and 215 mL of hydrochloric acid was heated to reflux for 2 hours. Upon completion of the reaction, it was cooled to room temperature and filtered. The collected solid was dissolved in 130 mL of water and neutralized to pH neutral with 20% sodium carbonate solution. The precipitate precipitated was filtered, washed several times with water and subsequently dried under vacuum in the presence of phosphoric acid. 5.4 g of product B was finally obtained in 96% yield.
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