1.Olefin oxygenation by water on an iridium center.
Ghatak T1, Sarkar M1, Dinda S1, Dutta I1, Rahaman SM1, Bera JK1. J Am Chem Soc. 2015 May 20;137(19):6168-71. doi: 10.1021/jacs.5b03055. Epub 2015 May 12.
Oxygenation of 1,5-cyclooctadiene (COD) is achieved on an iridium center using water as a reagent. A hydrogen-bonding interaction with an unbound nitrogen atom of the naphthyridine-based ligand architecture promotes nucleophilic attack of water to the metal-bound COD. Irida-oxetane and oxo-irida-allyl compounds are isolated, products which are normally accessed from reactions with H2O2 or O2. DFT studies support a ligand-assisted water activation mechanism.
2.Synthesis, Structure, and Conformational Dynamics of Rhodium and Iridium Complexes of Dimethylbis(2-pyridyl)borate.
Pennington-Boggio MK1, Conley BL1, Richmond MG2, Williams TJ1. Polyhedron. 2014 Dec 14;84:24-31.
Rhodium(I) and Iridium(I) borate complexes of the structure [Me2B(2-py)2]ML2 (L2 = (tBuNC)2, (CO)2, (C2H4)2, cod, dppe) were prepared and structurally characterized (cod = 1,5-cyclooctadiene; dppe = 1,2-diphenylphosphinoethane). Each contains a boat-configured chelate ring that participates in a boat-to-boat ring flip. Computational evidence shows that the ring flip proceeds through a transition state that is near planarity about the chelate ring. We observe an empirical, quantitative correlation between the barrier of this ring flip and the π acceptor ability of the ancillary ligand groups on the metal. The ring flip barrier correlates weakly to the Tolman and Lever ligand parameterization schemes, apparently because these combine both σ and π effects while we propose that the ring flip barrier is dominated by π bonding. This observation is consistent with metal-ligand π interactions becoming temporarily available only in the near-planar transition state of the chelate ring flip and not the boat-configured ground state.
3.Catalyst-controlled regiodivergent C-H borylation of multifunctionalized heteroarenes by using iridium complexes.
Sasaki I1, Taguchi J1, Hiraki S1, Ito H2, Ishiyama T3. Chemistry. 2015 Jun 15;21(25):9236-41. doi: 10.1002/chem.201500658. Epub 2015 May 12.
The regiodivergent C-H borylation of 2,5-disubstituted heteroarenes with bis(pinacolato)diboron was achieved by using iridium catalysts formed in situ from [Ir(OMe)(cod)]2 /dtbpy (cod=1,5-cyclooctadiene, dtbpy: 4,4'-di-tert-butyl-2,2'-bipyridine) or [Ir(OMe)(cod)]2 /2 AsPh3 . When [Ir(OMe)(cod)]2 /dtbpy was used as the catalyst, borylation at the 4-position proceeded selectively to afford 4-borylated products in high yields (dtbpy system A). The regioselectivity changed when the [Ir(OMe)(cod)]2 /2 AsPh3 catalyst was used; 3-borylated products were obtained in high yields with high regioselectivity (AsPh3 system B). The regioselectivity of borylation was easily controlled by changing the ligands. This reaction was used in the syntheses of two different bioactive compound analogues by using the same starting material.
4.Enantioselective Synthesis of Pyrrole-Based Spiro- and Polycyclic Derivatives by Iridium-Catalyzed Asymmetric Allylic Dearomatization and Controllable Migration Reactions.
Zhuo CX1, Cheng Q1, Liu WB1, Zhao Q1, You SL2. Angew Chem Int Ed Engl. 2015 Jul 13;54(29):8475-9. doi: 10.1002/anie.201502259. Epub 2015 Jun 3.
The first highly diastereo- and enantioselective synthesis of five-membered spiro-2H-pyrroles was achieved using an Ir-catalyzed asymmetric allylic dearomatization reaction. The spiro-2H-pyrrole derivatives readily undergo a controllable and stereospecific allylic migration under acid catalysis, providing polycyclic pyrrole derivatives in excellent yields and ee values. Additionally, the novel Ir-complex K1, derived from [Ir(cod)Cl]2 (cod = 1,5-cyclooctadiene) and N-benzhydryl-N-phenyldinaphthophosphoramidite (BHPphos), showed excellent control of both diastereo- and enantioselectivities.