Sodium borohydride → HCID 131736287, compound

Participants

Reaction Steps

Adapting literature known protocols (Osby and Ganem, Tetrahedron Lett., 1985, 26(52), 6413-6416), a mixture of nickel(II) dichloride hexahydrate (NiCl2.6H2O) (1.19 g, 5.0 mmol) in methanol (MeOH) (80 mL) is sonicated to effect complete dissolution. Solid sodium borohydride (NaBH4) (567 mg, 15.0 mmol) is added in small portions upon a black precipitate (Ni2B) is generated immediately and hydrogen gas is generated (exotherm!). After about 30 min, a solution of tert-butyl 4-(tert-butyl(dimethyl)silyl)oxy-4-(2-methyl-5-nitro-phenyl)-3-(nitromethyl)butanoate (17c) (4.69 g, 10.0 mmol) in MeOH (20 mL) is added followed by portion-wise addition of more NaBH4 (1.13 g, 30.0 mmol) at room temperature. The reaction is monitored by TLC and/or LCMS till completion. The reaction mixture is filtered over Celite® 545 and the filter residue is washed with additional MeOH. The combined filtrates are evaporated to dryness under reduced pressure using a rotary evaporator. The crude tert-butyl 3-(aminomethyl)-4-(5-amino-2-methyl-phenyl)-4-(tert-butyl(dimethyl)silyl)oxy-butanoate (17d) is used directly in the next step without further isolation and purification procedures.

Provenance & Evidence