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Retropinacol/Cross-pinacol Coupling Reactions - A Catalytic Access to 1,2-Unsymmetrical Diols
Published on: April 4, 2014
Dynamic Thermodynamic Resolution of Racemic 1,1'-Binaphthyl-2,2'-diol (BINOL)
Omer Shaashua1, Dennis Pollok2, Alina Dyadyuk1
1Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel.
Abstract:
A dynamic thermodynamic resolution method for converting (R/S)-BINOL (1,1'-binaphthyl-2,2'-diol) into (R)-BINOL in 100% theoretical yield is reported. This technique involves mixing (R/S)-BINOL with N-benzyl cinchonidinium bromide (1 equiv) and a [Cu2(tmeda)2(μ-OH)2]Br2 (2.5 mol %) redox catalyst in acetonitrile. In the background of this process is the observation that the energy for atropoisomerization decreases significantly when an electron is removed from BINOL. Therefore, it is possible to convert both enantiomers into the thermodynamically favorable [N-benzyl cinchonidinium bromide·(R)-BINOL] adduct.
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