Compound 1 is a salen-Ru complex which was developed by Katsuki et al. and is activated under visible light irradiation. When used as a catalyst, primary alcohols are selectively oxidized to aldehydes under aerobic conditions.¹ When a 1,n-diol, which has both primary and secondary hydroxyl groups, is oxidized in an atmosphere with 20% molecular oxygen, the corresponding lactols can be obtained.^1b Compound 1 can even use molecular oxygen at room temperature and therefore is not only an excellent catalyst in terms of atomic efficiency, but is also environmentally friendly.