26 June 2019
Overcoming heat limitation on important chemical compounds
Published online 18 May 2014
Scientists have synthesized carboranes at temperatures lower than 40°C by using complexed silver (I), opening the possibility to prepare these important compounds from thermally sensitive alkynes, which is impossible at high temperatures.
Carboranes are cage compounds made up of a cluster of boron atoms and two carbon atoms which form a polyhedron. They can attach to other chemical moeities whose properties lead to a wide range of applications, from cancer radiotherapy to solid superacids. The chemical synthesis has, until now, required high temperatures, limiting the range of chemical moieties that can be directly attached to carboranes.
The researchers, including Mohamed El-Zaria and Afaf Genady of Tanta University, Egypt, used a homogeneous silver (I) catalyst to produce high yield carboranes at temperatures as low as room temperature, publishing their results in Angewandte Chemie1 a.
Functionalized carboranes are synthesized by a chemical reaction between alkynes and boron-containing compounds. El-Zaria and his team hypothesized that using complexed silver (I) catalysts, known to enhance reactions involving addition to alkynes, might make it possible to lower the temperature for carborane synthesis.
To test this hypothesis, they added different alkynes to the boron-containing compounds at 40°C with and without the catalyst and compared the yield after a set period. The yields of the catalyzed reactions were more than two-fold higher in some cases.
El-Zaria, M.E. et al. High Yielding Synthesis of Carboranes Under Mild Reaction Conditions Using a Homogeneous Silver(I) Catalyst: Direct Evidence of a Bimetallic Intermediate. Angewandte Chemie (2014) doi:10.1002/anie.201311012