1: 65 percent / NaBH4 / methanol / 20 °C 2: 92 percent / (S)-2-phenyl-2,3-dihydrobenzo[d]imidazo[2,1-b]thiazole; Na2SO4 / CDCl3 / 48 h / 20 °C 3: CrO3; H2SO4 / acetone / 1 h / 20 °C 4: aq. HCl / methanol / Heating View Scheme

citrate buffer in water T=20°C; Mannich reaction; pH=4.0; 48 h; Title compound not separated from byproducts.;