N,N'-Bis(tert-butoxycarbonyl)-3-(trimethylsilyl)-2-propyne-1,1-diamine

Experimental procedure²⁾: To a solution of 1 (0.10 mmol) and diphenyl phosphate (2.5 mg, 0.010 mmol) in dichloromethane (2.0 mL) is added 3-phenylpropanal (0.30 mmol) at room temperature. After 1 is consumed, the reaction mixture is added CH₃OH (2.0 mL) and NaBH₄ (11 mg, 0.30 mmol) at 0 °C. After stirring for 2 h at 0 °C, the reaction mixture is quenched with water and extracted with EtOAc. The combined organic layers are washed with brine, dried over Na₂SO₄ and concentrated. The residue is purified by column chromatography on silica gel (eluting with hexane:EtOAc = 7:1, then toluene:EtOAc = 20:1) to afford the corresponding aminoalcohol in 50% yield.