1. Crystal structures of two PCN pincer iridium complexes and one PCP pincer carbodi-phospho-rane iridium inter-mediate: substitution of one phosphine moiety of a carbodi-phospho-rane by an organic azide
Gabriel Julian Partl, Felix Nussbaumer, Walter Schuh, Holger Kopacka, Klaus Wurst, Paul Peringer Acta Crystallogr E Crystallogr Commun. 2019 Jan 1;75(Pt 1):75-80. doi: 10.1107/S2056989018017644.
The structure of [Ir{(4-Cl-C6H4N3)C(dppm)-κ3 P,C,N}(dppm-κ2 P,P')]Cl·1.5CH2Cl2·0.5C7H8 (C57H48Cl2IrN3P4·1.5CH2Cl2·0.5C7H8) (2), dppm = bis-(di-phenyl-phosphino)methane {systematic name: [7-(4-chloro-phen-yl)-1,1,3,3-tetra-phenyl-5,6,7-tri-aza-κN 7-1,3λ4-diphospha-κP 1-hepta-4,6-dien-4-yl][methyl-ene-bis(di-phenyl-phosphine)-κ2 P,P']iridium(I) chloride-di-chloro-methane-toluene (2/3/1)}, resulting from the reaction of [IrClH{C(dppm)2-κ3 P,C,P)(MeCN)]Cl (1a) with 1-azido-4-chloro-benzene, shows a monocationic five-coordinate IrI complex with a distorted trigonal-bipyramidal geometry. In 2, the iridium centre is coordinated by the neutral triazeneyl-idene-phospho-rane (4-Cl-C6H4N3)C(dppm) acting as a PCN pincer ligand, and a chelating dppm unit. The structure of the coordination compound [IrCl(CN)H(C(dppm)2-κ3 P,C,P)]·CH3CN, (C52H45ClIrNP4·CH3CN) (1b) [systematic name: chlorido-cyanidohydrido(1,1,3,3,5,5,7,7-octa-phenyl-1,3λ5,5λ4,7-tetra-phospha-κ2 P 1,P 7-hept-3-en-4-yl)iridium(III) aceto-nitrile monosolvate], prepared from 1a and KCN, reveals an octa-hedral IrIII central atom with a meridional PCP pincer carbodi-phospho-rane (CDP) ligand; the chloride ligand is located trans to the central carbon of the CDP functionality while the hydrido and cyanido ligands are situated trans to each other. The chiral coordination compound [Ir(CN)((4-Cl-C6H4N3)CH(CH(P(Ph)2)2)-κ3 P,C,N)(dppm-κ2 P,P')]·2CH3OH, (C58H48ClIrN4P4·2CH3OH) (3) (systematic name: {4-[3-(4-chloro-phen-yl)triazenido-κN 3]-1,1,3,3-tetra-phenyl-1,3λ5-diphospha-κP 1-but-2-en-4-yl}cyanido[methyl-enebis(di-phenyl-phosphine)-κ2 P,P']iridium(III) methanol disolvate), formed via prolonged reaction of 1-azido-4-chloro-benzene with 1b, features a six-coordinate IrIII central atom. The iridium centre is coordinated by the dianionic facial PCN pincer ligand [(4-Cl-C6H4N3)CH(CH(P(Ph2)2)2)], a cyanido ligand trans to the central carbon of the PCN pincer ligand and a chelating dppm unit. Complex 2 exhibits a 2:1 positional disorder of the Cl- anion. The CH2Cl2 and C7H8 solvent mol-ecules show occupational disorder, with the toluene mol-ecule exhibiting additional 1:1 positional disorder with some nearly overlying carbon atoms.
2. Synthesis of 1,4-dideoxy-1,4-imino-D-glucitol, a glucosidase inhibitor
J Kuszmann, L Kiss Carbohydr Res. 1986 Sep 15;153(1):45-53. doi: 10.1016/s0008-6215(00)90194-0.
1,2:5,6-Di-O-isopropylidene-D-glucitol was converted via its 1,4-dimethanesulfonate into the 1-azido-4-methanesulfonate which, after deprotection and treatment with barium hydroxide, afforded a 9:1 mixture of the corresponding 3,4- and 4,5-anhydro derivatives. Reduction of this mixture by transfer hydrogenation using ammonium formate in methanol and Pd/C as catalyst afforded 1,4-dideoxy-1,4-imino-D-glucitol (4), the structure of which was proved after acetylation by 1H-n.m.r. spectroscopy. Compound 4 is a potent alpha-D-glucosidase inhibitor (Ki 7 X 10(-4)M) and a less potent beta-D-glucosidase inhibitor (Ki 1.25 X 10(-4)M), and inhibits beta-D-galactosidase non-competitively.
3. Catalytic Synthesis of N-Heterocycles via Direct C(sp3)-H Amination Using an Air-Stable Iron(III) Species with a Redox-Active Ligand
Bidraha Bagh, et al. J Am Chem Soc. 2017 Apr 12;139(14):5117-5124. doi: 10.1021/jacs.7b00270. Epub 2017 Mar 28.
Coordination of FeCl3 to the redox-active pyridine-aminophenol ligand NNOH2 in the presence of base and under aerobic conditions generates FeCl2(NNOISQ) (1), featuring high-spin FeIII and an NNOISQ radical ligand. The complex has an overall S = 2 spin state, as deduced from experimental and computational data. The ligand-centered radical couples antiferromagnetically with the Fe center. Readily available, well-defined, and air-stable 1 catalyzes the challenging intramolecular direct C(sp3)-H amination of unactivated organic azides to generate a range of saturated N-heterocycles with the highest turnover number (TON) (1 mol% of 1, 12 h, TON = 62; 0.1 mol% of 1, 7 days, TON = 620) reported to date. The catalyst is easily recycled without noticeable loss of catalytic activity. A detailed kinetic study for C(sp3)-H amination of 1-azido-4-phenylbutane (S1) revealed zero order in the azide substrate and first order in both the catalyst and Boc2O. A cationic iron complex, generated from the neutral precatalyst upon reaction with Boc2O, is proposed as the catalytically active species.
