N-Halosaccharins Usable for Halogenations

N-Halosaccharins (X = Cl (1), X = Br (2), X = I (3)) are solid compounds which are easy to handle and can be used as electrophilic halogenating reagents. For example, by treating 1,3-diketone 4 with lithium perchlorate and each halogenating agent, α-halogenated 1,3-diketones are given in high yields. On the other hand, when a high electron-withdrawing difluoroboryl group-coordinated alkoxy borane complex 5 is treated with halogenating agents, halogenations at the 3,5-dimethoxyphenyl moiety of 5 proceed and the related 2,6-dihalogenated compounds are given in high yields and high regioselectivity. In this way, N-halosaccharins can be effectively used for regioselective halogenations of active methylene compounds and aromatic rings.