Formaldehyde → (S)-3-amino-1-((1S,2R,4R)-4-(isopropyl(methyl)amino)-2-propylcyclohexyl)pyrrolidin-2-one

Participants

Reaction Steps

The entirety of benzyl (S)-1-[(1S,2R,4R)-4-(isopropyl(methyl)amino)-2-propylcyclohexyl]-2-oxopyrrolidin-3-ylcarbamate prepared in Step 2 (assumed 8.2 mmol) was wet with 3 mL of EtOAc and then charged with 30% HBr/AcOH (30 mL). The reaction vessel warms and a vigorous gas evolution occurs. The mixture was stirred for 25 min at RT and then the flask was placed in a cool water bath before the addition of 150 mL of 1:1 Et2O/H2O. This mixture was mixed and separated, and the aqueous phase was extracted once with Et2O. The aqueous phase was basified to pH 14 through the addition of solid NaOH (the temperature of this exothermic process was controlled through the intermittent use of an external ice bath) and the resulting mixture was extracted with EtOAc (75 mL, then 2×35 mL). The organic extracts were combined, washed with brine (30 mL), dried (Na2SO4), filtered, and concentrated in vacuo to give an orange oil, contaminated with some powdery white solid (presumed to be formaldehyde-related). The mixture was dissolved in a minimal volume of EtOAc, filtered, and concentrated to provide (S)-3-amino-1-[(1S,2R,4R)-4-(isopropyl(methyl)amino)-2-propylcyclohexyl]pyrrolidin-2-one (2.31 g; 1H-NMR shows ˜30% EtOAc, indicating an estimated 7.0 mmol of product from Steps 1–3). MS found: (M+H)+=296.6.

Provenance & Evidence