Yield:-

Reaction Conditions:

Stage #1: 6-nitro-1,2,3,4-tetrahydro-9H-carbazol-1-onewith ammonium acetate in methanol at 23;
Stage #2: with sodium cyanoborohydride in methanol at 60;

Steps:

General procedure to prepare racemic amines iv (1-20)

General procedure: Solid NH₄OAc (5.0 mmol) was added to a stirring solution of requisite ketone iii (0.5 mmol) dissolved in 20 mL solvent grade CH₃OH, and this mixture was allowed to stir at room temperature (23 °C) for 3-6 h. Upon complete consumption of iii, as determinedby thin layer chromatography, solid NaCNBH₃ (2.5 mmol) was added andthe temperature was raised to 60 °C. After stirring 12-16 h, the reaction was cooled to room temperature (23 °C) and treated with an aqueous 1 M HCl solution. The mixture was extracted with ethyl acetate, and the combined organic layers were washed with brine and dried over anhydrous Na₂SO₄, filtered, and concentrated under reduced pressure to afford the crude product. The desired product was purified by flash column chromatography (SiO₂) using CH₂Cl₂ and CH₃OH as the eluent. NMR of products were compared to literature values to confirm structure.

References:

Li, Yangxiong;Gardner, Jessi J.;Fortney, Katherine R.;Leus, Inga V.;Bonifay, Vincent;Zgurskaya, Helen I.;Pletnev, Alexandre A.;Zhang, Sheng;Zhang, Zhong-Yin;Gribble, Gordon W.;Spinola, Stanley M.;Duerfeldt, Adam S. [Bioorganic and Medicinal Chemistry Letters,2019,vol. 29,# 14,p. 1836 - 1841] Location in patent:supporting information