In a similar method as used for 3, 3-methylquinoline (1a) was introduced into the NHPI–Co–Mn system. However, no oxidation took place, and 1a was recovered unchanged (Scheme 2). It was found that the color of the AcOH solution of NHPI–Co–Mn changed from pink, based on Co(II), to light purple on addition of 1a. A similar color change was observed when 1a was added to an AcOH solution of Co(OAc) 2 , but the addition of 3 to this solution led to almost no ...
