Chiral CpxRhIII-Catalyzed Enantioselective C-H Annulation to Access Fused Tricyclic Sulfur-Stereogenic and Medium-sized aza-Heterocycles

Abstract

We report herein a chiral CpxRhIII-catalyzed asymmetric sp2 C-H bond activation/annulation reaction of free NH-sulfoximines with hypervalent iodonium ylides under external ligand-free conditions was reported. Efficient kinetic resolution (KR) was observed for the reactions of racemic sulfoximines bearing an asymmetric S-aryl-S-alkyl moiety, which also delivered the expected fused tricyclic (S)-aza-heterocycles and the corresponding chiral (R)-NH-sulfoximines in mostly good yields and excellent enatioselectivities. By use of this catalytic protocol, structurally unprecedented 10-membered S-stereogenic benzothiazecines with nice enantioselectivities could be achieved upon one-pot multi-step oxidation reactions. Mechanistically, an enantiodetermined C−H cleavage and the subsequent formation of a chiral five-membered rhodacycle intermediate were supposed through systematic deuterium (D) labeled studies.