Chemoselective N-deprotection of tert-butyl 2-(trifluoroacetylamino) esters under PTC conditions: Synthesis of tert-butyl 2-aminocarboxylates

Trifluoroacetamide 1 is alkylated in good yields (77-83%) by tert-butyl 2-bromocarboxylates 3 under solid-liquid phase transfer catalysis (PTC) conditions [anhydrous K2CO3, triethyl(benzyl)ammonium chloride (TEBA; 10%), MeCN, 80 degrees C], The resulting tert-butyl 2-(trifluoroacetylamino) carboxylates 5 are chemoselectively hydrolysed in 75-95% yields to the corresponding tert-butyl 2-amino carboxylates, isolated as hydrochlorides 8, under liquid-liquid PTC conditions [CH2Cl2 or Et(2)O, aqueous 20% KOH, TEBA (10%), 25-40 degrees C].