Enantioselective Intramolecular Iridium-Catalyzed Cyclopropanation of α-Carbonyl Sulfoxonium Ylides

Enantioselective cyclopropanation of alpha-carbonyl sulfoxo-nium ylides (SY) has so far been limited to addition/ring closure reactions on electron-poor olefins. Herein, we report the iridium-catalyzed intramolecular cyclopropanation of SY in the presence of a chiral diene in up to 96% yield and 98% enantioselectivity. Moreover, density functional theory calculations suggest that the re face of the olefin preferably attacks an iridium carbene intermediate in an asynchronous concerted step that is independent of the geometry of the olefin. 00 / 0 I1 X'jf Ir(I) cat./L" 1,2-DCE, r.t. H R2 R3 R3 X = 0, NR, CH2; n = 1, 2; R1 -R3 = H (hetero)aryl, alkenyl, alkyl L" Ph Ph from DFT studies