Transfer Hydrogenation of Alkenes Using Ethanol Catalyzed by a NCP Pincer Iridium Complex: Scope and Mechanism.

The first general catalytic approach to effecting transfer hydrogenation (TH) of unactivated alkenes using ethanol as the hydrogen source is described. A new NCP-type pincer iridium complex (BQ-NCOP)IrHCl containing a rigid benzoquinoline backbone has been developed for efficient, mild TH of unactivated C-C multiple bonds with ethanol, forming ethyl acetate as the sole byproduct. A wide variety of alkenes, including multisubstituted alkyl alkenes, aryl alkenes, and heteroatom-substituted alkenes, as well as O- or N-containing heteroarenes and internal alkynes, are suitable substrates. Importantly, the (BQ-NCOP)Ir/EtOH system exhibits high chemoselectivity for alkene hydrogenation in the presence of reactive functional groups, such as ketones and carboxylic acids. Furthermore, the reaction with C2D5OD provides a convenient route to deuterium-labeled compounds. Detailed kinetic and mechanistic studies have revealed that monosubstituted alkenes (e.g., 1-octene, styrene) and multisubstituted alkenes (e.g., cyclooctene (COE)) exhibit fundamental mechanistic difference. The OH group of ethanol displays a normal kinetic isotope effect (KIE) in the reaction of styrene, but a substantial inverse KIE in the case of COE. The catalysis of styrene or 1-octene with relatively strong binding affinity to the Ir(I) center has (BQ-NCOP)IrI(alkene) adduct as an off-cycle catalyst resting state, and the rate law shows a positive order in EtOH, inverse first-order in styrene, and first-order in the catalyst. In contrast, the catalysis of COE has an off-cycle catalyst resting state of (BQ-NCOP)IrIII(H)[O(Et)···HO(Et)···HOEt] that features a six-membered iridacycle consisting of two hydrogen-bonds between one EtO ligand and two EtOH molecules, one of which is coordinated to the Ir(III) center. The rate law shows a negative order in EtOH, zeroth-order in COE, and first-order in the catalyst. The observed inverse KIE corresponds to an inverse equilibrium isotope effect for the pre-equilibrium formation of (BQ-NCOP)IrIII(H)(OEt) from the catalyst resting state via ethanol dissociation. Regardless of the substrate, ethanol dehydrogenation is the slow segment of the catalytic cycle, while alkene hydrogenation occurs readily following the rate-determining step, that is, ß-hydride elimination of (BQ-NCOP)Ir(H)(OEt) to form (BQ-NCOP)Ir(H)2 and acetaldehyde. The latter is effectively converted to innocent ethyl acetate under the catalytic conditions, thus avoiding the catalyst poisoning via iridium-mediated decarbonylation of acetaldehyde.

[Effect of Toxoplasma gondii Infection in Female Mice on Dopamine Level in the Brain of the Male Offspring].

OBJECTIVE: To investigate the effect of Toxoplasma gondii infection in female mice on dopamine level in the brain of male offspring. METHODS: Thirty-six ICR female mice were randomly divided into control group and infection group, 18 mice in each group. Each mouse in infection group was orally infected with 10 cysts of T. gondii Prugniaud strain. On the 90th day after infection, the infected female mice were mated with normal male ICR mice at 1:1 ratio. On the 20th day of pregnancy, 2 mice in each group were delivered for fetal mice by cesarean section, and the brain of male fetal mice (n = 6) in each group were collected. On the 14th and 63rd day after birth, 6 male offspring mice in each group were sacrificed, and the brain were collected. Dopamine levels in the cortex, cerebellum, hippocampus, and striatum were analyzed by high-performance liquid chromatography-electrochemical detection (HPLC-ECD). RESULTS: Three mice in infection group died during the experiment, and 6 out of 15 female mice mated successfully. The number of fetal mice and F1 generation mice in infection group was 12 (male: 7) and 21 (male: 15), respectively. All the mice in control group mated successfully. The number of fetal mice and F1 generation mice was 23 (male: 12) and 179 (male: 92), respectively. The dopamine level in the cerebellum of fetal mice of infection group and control group was (413.25 ± 21.78) ng/g and (346.30 ± 51.83) ng/g, respectively (P < 0.01). No significant difference was found in dopamine content in the cortex between the two groups (P > 0.05). Compared with the control group, on the 14th day and 63rd day after birth, the dopamine content in cortical areas [(462.50 ± 24.80) ng/g and (1215.77 ± 113.64) ng/g], cerebellum area [(271.55 ± 26.19) ng/g and (1328.82 ± 39.62) ng/g], hippocampus area [(225.78 ± 24.17) ng/g and (1322.70 ± 58.34) ng/g], and striatum area [(455.23 ± 61.53) ng/g and (991.32 ± 54.31) ng/g] of the male offspring in infection group were significantly higher than that of the control (P < 0.05, P < 0.01). CONCLUSION: T. gondii infection in female mice causes an increase of dopamine level in the brain of F1 generation male mice.

Highly enantioselective fluorescent recognition of serine and other amino acid derivatives.

The BINOL-amino alcohol compound (S)-4 was found to conduct enantioselective fluorescent recognition of a serine derivative with an unprecedented high ef [enantioselective fluorescent enhancement = (I(D) - I(0))/(I(L) - I(0))] of 12.5. Both (S)-4 and (S)-5 are also found to be highly enantioselective fluorescent sensors for a number of other amino acid derivatives.

Novel dimetal bridging carbene complexes derived from a terminal carbonyl dimetal compound. Syntheses, structures and reactivities of 7H-indene-coordinated diiron bridging carbene complexes.

Pentacarbonyl-7H-indenediiron, [Fe2(CO)5(eta3,eta5-C9H8)] (1), reacts with aryllithium, ArLi (Ar = C6H5, p-C6H5C6H4), followed by alkylation with Et3OBF4 to give novel 7H-indene-coordinated diiron bridging alkoxycarbene complexes [Fe2{mu-C(OC2H5)Ar}(CO)4(eta4,eta4-C9H8)] (2, Ar = C6H5; 3, Ar = p-C6H5C6H4). Complexes 2 and 3 react with HBF4.Et2O at low temperature to yield cationic bridging carbyne complexes [Fe2(mu-CAr)(CO)4(eta4,eta4-C9H8)]BF4 (4, Ar = C6H5; 5, Ar = p-C6H5C6H4). Cationic 4 and 5 react with NaBH4 in THF at low temperature to afford diiron bridging arylcarbene complexes [Fe2{mu-C(H)Ar}(CO)4(eta4,eta4-C9H8)] (6, Ar = C6H5; 7, Ar = p-C6H5C6H4). The similar reactions of 4 and 5 with NaSC6H4CH3-p produce the bridging arylthiocarbene complexes [Fe2{mu-C(Ar)SC6H4CH3-p}(CO)4(eta4,eta4-C9H8)] (8, Ar = C6H5; 9, Ar = p-C6H5C6H4). Cationic 4 and 5 can also react with anionic carbonylmetal compounds Na[M(CO)5(CN)] (M = Cr, Mo, W) to give the diiron bridging aryl(pentacarbonylcyanometal)carbene complexes [Fe2{mu-C(Ar)NCM(CO)5}(CO)4(eta4,eta4-C9H8)] (10, Ar = C6H5, M = Cr; 11, Ar = p-C6H5C6H4, M = Cr; 12, Ar = C6H5, M = Mo; 13, Ar = p-C6H5C6H4, M = Mo; 14, Ar = C6H5, M = W; 15, Ar = p-C6H5C6H4, M = W). Interestingly, in CH2Cl2 solution at room temperature complexes 10-15 were transformed into the isomerized 7H-indene-coordinated monoiron complexes [Fe(CO)2(eta5-C9H8)C(Ar)NCM(CO)5] (16, Ar = C6H5, M = Cr; 17, Ar = p-C6H5C6H4, M = Cr; 18, Ar = C6H5, M = Mo; 19, Ar = p-C6H5C6H4, M = Mo; 20, Ar = C6H5, M = W; 21, Ar = p-C6H5C6H4, M = W), while complex 3 was converted into a novel ring addition product [Fe2{C(OC2H5)C6H4C6H5-p-(eta2,eta5-C9H8)}(CO)5] (22) under the same conditions. The structures of complexes 2, 6, 8, 14, 18 and 22 have been established by X-ray diffraction studies.