High sensitivity and broad dynamic range infrared multiphoton dissociation for a quadrupole ion trap

Dynamic control of bath gas pressure in a quadrupole ion trap (QIT) achieved high sensitivity and broad dynamic range infrared multiphoton dissociation (IRMPD). Conventional IRMPD is not sensitive because the bath gas pressure in the QIT needs to be kept at less than 1 mTorr for an effective dissociation, whereas the pressure should be about 20 mTorr for maximum trapping efficiency during ion accumulation. By switching the bath gas pressure between about 20 mTorr during the ion accumulation period and less than 0.6 mTorr during the IRMPD period, it was possible to achieve both maximum trapping efficiency and effective IRMPD. An optimized method for gas introduction enables the trapping efficiency to remain constant during the accumulation period, which permits a broad dynamic range measurement.     

Addition reaction of zinc acetylides to thioiminium salts leading to 3-amino-1-sulfenyl-1,4-enynes

The reaction of thioiminium salts with zinc acetylides took place at 60 °C to give 3-amino-1-sulfenyl-1,4-enynes in moderate to good yields. Two molecules of acetylides were incorporated into the products. Nucleophilic attack of zinc acetylides to thioiminium salts may initially occur to form alkynyl S,N-acetals, followed by their [1,3]-rearrangement to give 3-sulfenyl-1-aminoallenes.     

Catalytic Reduction of Dinitrogen into Ammonia and Hydrazine by Using Chromium Complexes Bearing PCP-Type Pincer Ligands**

A series of chromium-halide, -nitride, and -dinitrogen complexes bearing carbene- and phosphine-based PCP-type pincer ligands has been newly prepared, and some of them are found to work as effective catalysts to reduce dinitrogen under atmospheric pressure, whereby up to 11.60 equiv. of ammonia and 2.52 equiv. of hydrazine (16.6 equiv. of fixed N atom) are produced based on the chromium atom. To the best of our knowledge, this is the first successful example of chromium-catalyzed conversion of dinitrogen to ammonia and hydrazine under mild reaction conditions.     

Synthesis of highly luminescent organoboron polymers connected by bifunctional 8‐aminoquinolate linkers

New organoboron aminoquinolate‐based polymers linked by π‐conjugated bridge were prepared by Sonogashira–Hagihara coupling of organoboron aminoquinolate‐based bisiodo monomers bearing biphenyl or bithiophene moiety with 1,4‐diethynylbenzene derivatives. Tetracoordination states of boron atoms in the obtained polymers were confirmed by ¹¹B NMR spectroscopy, and they were also characterized by ¹H NMR and IR spectroscopies and size‐exclusion chromatography. Their optical properties were studied by UV–vis absorption and photoluminescence spectroscopies. In the region above 400 nm, the polymers prepared from 1,4‐diethynyl‐2,5‐dioctyloxybenzene showed bathochromic shifts when compared with those prepared from 1.4‐diethynyl‐2‐perfluorooctyl‐5‐trifluoromethylbenzene. The polymers with biphenyl moiety showed higher absolute fluorescence quantum yields (?_F = 0.28 and 0.65), whereas those with bithiophene moiety led to decreasing of the low quantum yields (?_F = 0.19 and 0.00). The density‐functional theory (DFT) and time‐dependent–DFT calculations of model compounds corresponding to the polymers were in good agreement with the results from UV–vis properties. The calculations revealed that the electronic structure of the polymer with bithiophene moiety is different from that with biphenyl moiety, and predicted the electron transfer from the bithiophene moiety to the π‐extended quinoline moiety in transition state. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3693–3701, 2010     

(E)‐,(Z)‐Parallel Preparative Methods for Stereodefined β,β‐Diaryl‐ and α,β‐Diaryl‐α,β‐unsaturated Esters: Application to the Stereocomplementary Concise Synthesis of Zimelidine

Parallel and practical methods for the preparation of both (E)‐ and (Z)‐β‐aryl¹‐β‐aryl²‐α,β‐unsaturated esters 1 and (E)‐ and (Z)‐α‐aryl¹‐β‐aryl²‐α,β‐unsaturated esters 2 are described. These methods involve accessible, robust, stereocomplementary N‐methylimidazole (NMI)‐mediated enol tosylations (14 examples, 70–99 % yield), as well as stereoretentive Suzuki–Miyaura cross‐couplings (36 examples, 64–99 % yield). The highlighted feature of the present protocol is the use of parallel and stereocomplementary approaches to obtain highly (E)‐ and (Z)‐pure products 1 and 2 by utilizing sequential enol tosylations and cross‐coupling reactions. An expeditious and parallel synthesis of (E)‐ and (Z)‐zimelidine ( 3 ), which is a highly representative selective serotonin reuptake inhibitor (SSRI), was performed by utilizing the present methods.     

Nickel-catalysed intramolecular alkene insertion into cyclobutanones

A nickel(0) catalyst converted 3-styrylcyclobutanones into benzobicyclo[2.2.2]octenones by an intramolecular insertion of the vinyl moiety into the cyclobutanone skeleton.     

Novel immobilization method of enzymes using a hydrophilic polymer support

A novel immobilization of an enzyme with a hydrophilic polymer support in organic solvents has been developed utilizing the "polymer-incarcerated (PI) method", which has been used to immobilize metal catalysts; the kinetic resolution of secondary alcohols was found to proceed more smoothly using immobilized lipases (CALB) than free lipases.     

Intermolecular interaction and a concentration-quenching mechanism of phosphorescent Ir(III) complexes in a solid film

Solid-state self-quenching processes of highly efficient Ir(III) phosphorescent emitters are investigated by the measurement of thin film photoluminescence quantum efficiency and transient lifetime as a function of doping concentration in a host matrix. The radiative decay rate constant is found to be independent from the average distance between dopant molecules (R), and the concentration-quenching rate constant is shown to be dependent on R(-6). The quenching dependence on R strongly suggests that luminescent concentration quenching in a phosphorescent Ir(III) complex:host film is controlled by dipole-dipole deactivating interactions as described by the F?rster energy transfer model.