Synthesis
GENERAL METHOD: Carboxylic acid amide (20 mmol) was dissolved in dichloromethane (10 mL), triethyloxonium tetrafluoroborate (4.18 g, 22 mmol) was added, and stirred (A) overnight or (B) for 3 hours at room temperature. The reaction was carried out in a water bath at 40 °C under argon protection. Upon completion of the reaction, the mixture was concentrated under vacuum and the residue was dissolved in 20 mL of anhydrous ethanol. The solution was transferred to an autoclave pre-cooled in an ice bath, the catalyst (1 mol%) and 10 ml of ethanol solution of 2M sodium methanol were added, flushed with argon and injected with 40 bar of hydrogen. The reaction mixture was stirred at 25 °C and constant pressure until hydrogen uptake was no longer evident (reaction time 1-12 h). The reaction solution was filtered through diatomaceous earth and the filtrate was mixed with 11 ml of 2N hydrochloric acid and washed with ether. The aqueous phase was alkalized with 14 ml of 2N sodium hydroxide solution and the amine was extracted with ether. The organic phases were combined and dried with anhydrous potassium carbonate. Removal of the solvent in vacuum gave the almost pure amine product (0186). The specific catalysts used and the corresponding yields are detailed in Table 6.
