Zinc-mediated efficient and selective reductive aza-Claisen rearrangement of N-allyl- and N-propargylaminoanthraquinones in ionic liquid

An efficient method is described for the first time for reductive aza-Claisen rearrangement of 1-(N-allylamino)anthraquinones to 1-amino-2-(prop-2'-enyl)anthraquinones using zinc powder in 1-methylimidazolium tetrafluoroborate ([Hmim] BF₄) as an ionic liquid in good to excellent yields. Extending of this method on 1-(N-propargylamino)anthraquinones causes the production of 1,2,3,4-tetrahydronaphtho[2,3-h]quinoline-7,12-diones containing a newly synthesized six membered heterocyclic ring on anthraquinone core via performing this reductive [3,3] sigmatropic reaction followed by cyclization in a tandem manner. These rearrangements can be executed even in the presence of some other functional groups with excellent chemoselectivity.