Highly Active Water-Soluble Olefin Metathesis Catalyst

A novel water-soluble ruthenium olefin metathesis catalyst supported by a poly(ethylene glycol) conjugated saturated 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene ligand is reported. The catalyst displays improved activity in ring-opening metathesis polymerization, ring-closing metathesis, and cross-metathesis reactions in aqueous media

Decomposition of a Key Intermediate in Ruthenium-Catalyzed Olefin Metathesis Reactions

Dinuclear ruthenium complex, with a bridging carbide and a hydride ligand, and methyltricyclohexylphosphonium chloride result from thermal decomposition of olefin metathesis catalyst, (ImesH_2)(PCy)_3)(Cl)_2Ru CH_2. Involvement of dissociated phosphine in the decomposition is proposed. The dinuclear complex has catalytic olefin isomerization activity, which can be responsible for competing isomerization processes in certain olefin metathesis reactions

Prevention of Undesirable Isomerization during Olefin Metathesis

1,4-Benzoquinones have been found to prevent olefin isomerization of a number of allylic ethers and long-chain aliphatic alkenes during ruthenium-catalyzed olefin metathesis reactions. Electron-deficient benzoquinones are the most effective additives for the prevention of olefin migration. This mild, inexpensive, and effective method to block olefin isomerization increases the synthetic utility of olefin metathesis via improvement of overall product yield and purity

Decomposition of Ruthenium Olefin Metathesis Catalysts

The decomposition of a series of ruthenium metathesis catalysts has been examined using methylidene species as model complexes. All of the phosphine-containing methylidene complexes decomposed to generate methylphosphonium salts, and their decomposition routes followed first-order kinetics. The formation of these salts in high conversion, coupled with the observed kinetic behavior for this reaction, suggests that the major decomposition pathway involves nucleophilic attack of a dissociated phosphine on the methylidene carbon. This mechanism also is consistent with decomposition observed in the presence of ethylene as a model olefin substrate. The decomposition of phosphine-free catalyst (H_2IMes)(Cl)_2Ru CH(2-C_6H_4-O-i-Pr) (H_2IMes = 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene) with ethylene was found to generate unidentified ruthenium hydride species. The novel ruthenium complex (H_2IMes)(pyridine)_3(Cl)_2Ru, which was generated during the synthetic attempts to prepare the highly unstable pyridine-based methylidene complex (H_2IMes)(pyridine)_2(Cl)_2Ru CH_2, is also reported

Low Catalyst Loadings in Olefin Metathesis: Synthesis of Nitrogen Heterocycles by Ring-Closing Metathesis

A series of ruthenium catalysts have been screened under ring-closing metathesis (RCM) conditions to produce five-, six-, and seven-membered carbamate-protected cyclic amines. Many of these catalysts demonstrated excellent RCM activity and yields with as low as 500 ppm catalyst loadings. RCM of the five-membered carbamate series could be run neat, the six-membered carbamate series could be run at 1.0 M, and the seven-membered carbamate series worked best at 0.2−0.05 M

Development of a standardized in-hospital cardiopulmonary resuscitation set-up

Objective. This study evaluated whether chest compression in a standardized inhospital cardiopulmonary resuscitation (CPR) set-up can be performed as effectively as when the rescuer is kneeling beside the patient lying on the floor. Specifically, the in-hospital test was standardized according to the rescuers’ average knee height. Methods. Experimental intervention (test 1) was a standardized, in-hospital CPR set-up: first, the bed height was fixed at 70 cm. Second, the height difference between the bed and a step stool was set to the average knee height of the CPR team members (45 cm). Control intervention (test 2) was kneeling on floor. Thirty-eight medical doctors on the CPR team each performed 2 minutes of chest compressions in test 1 and 2 in random order (cross-over trial). A Little Anne was used as a simulated patient who had experienced cardiac arrest. Chest compression parameters, such as average depth and rate, were measured using an accelerometer device. Results. In all tests, the average depths were those recommended in the most recent CPR guidelines (50–60 mm); there were no significant differences between Tests 1 and 2 (53.1 ± 4.3 mm vs. 52.6 ± 4.8 mm, respectively; p = 0.398). The average rate in Test 2 (119.1 ± 12.4 numbers/min) was slightly faster than that in Test 1 (116.4 ± 10.2 numbers/ min; p = 0.028). No differences were observed in any other parameters. Conclusions. Chest compression quality in our standardized in-hospital CPR set-up was similar with that performed in a kneeling position on the floor. Trial Registration: Clinical Research Information Service: KCT000159