Stereoselective Bromoboration of Acetylene with Boron Tribromide: Preparation and Cross-Coupling Reactions of (Z)-Bromovinylboronates.

The mechanism of acetylene bromoboration in neat boron tribromide was studied carefully by means of experiment and theory. Besides the syn-addition mechanism through a four-center transition state, radical and polar anti-addition mechanisms are postulated, both triggered by HBr, which is evidenced also to take part in the Z/E isomerization of the product. The proposed mechanism is well supported by ab initio calculations at the MP2/6-31+G* level with Ahlrichs' SVP all-electron basis for Br. Implicit solvation in CH2Cl2 has been included using the PCM and/or SMD continuum solvent models. Comparative case studies have been performed involving the B3LYP/6-31+G* with Ahlrichs' SVP for Br and MP2/Def2TZVPP levels. The mechanistic studies resulted in development of a procedure for stereoselective bromoboration of acetylene yielding E/Z mixtures of dibromo(bromovinyl)borane with the Z-isomer as a major product (up to 85%). Transformation to the corresponding pinacol and neopentyl glycol boronates and stereoselective decomposition of their E-isomer provided pure (Z)-(2-bromovinyl)boronates in 57-60% overall yield. Their reactivity in a Negishi cross-coupling reaction was tested. An example of the one-pot reaction sequence of Negishi and Suzuki-Miyaura cross-couplings for synthesis of combretastatin A4 is also presented.

Survival after cardiac arrest and changing task profile of the cardiac arrest team in a tertiary care center.

BACKGROUND: The characteristics of in-hospital emergency response systems, survival rates, and variables associated with survival after in-hospital cardiac arrest vary significantly among medical centers worldwide. Aiming to optimize in-hospital emergency response, we performed an analysis of survival after in-hospital cardiopulmonary resuscitation and the task profile of our cardiac arrest team. METHODS: In-hospital emergencies handled by the cardiac arrest team in the years 2004 to 2006 were analyzed retrospectively, and patient and event characteristics were tested for their associations with survival after cardiopulmonary resuscitation. The results were compared to a similar prior analysis for the years 1995 to 1997. RESULTS: After cardiopulmonary resuscitation, the survival rate to discharge was 30.2% for the years 2004 to 2006 compared to 25.1% for the years 1995 to 1997 (difference not statistically significant). Survival after one year was 18.5 %. An increasing percentage of emergency calls not corresponding to medical emergencies other than cardiac arrest was observed. CONCLUSIONS: The observed survival rates are considerably high to published data. We suggest that for further improvement of in-hospital emergency response systems regular training of all hospital staff members in immediate life support is essential. Furthermore, future training of cardiac arrest team members must include basic emergency response to a variety of medical conditions besides cardiac arrest.