The N-oxide is transformed to N-tert-butylamino intermediate and then deprotected in situ with TFA in a one-pot operation. The procedure works well with a wide variety of substrates: pyridines, quinolines, isoquinolines. The few examples of unsymmetrically-substituted pyridine-oxides that had both the 2 and 6 positions free provided a mix of the two ortho amino regioisomers. [This is an improved version of the amination procedure with TsCl, NH3 that was useful for 2-aminoquinoline scale-up: Couturier et al, Org Process R & D, 10 (2006), 534-8.]
Another related simple procedure for acylamidation of N-oxides from Pfizer process group uses RCONCO that is generated generated in situ from RCONH2 and oxalyl chloride:
This acylamination procedure is however limited to quinolines, isoquinolines and phenanthrolines; pyridine N-oxides fail in the acylamidation.