Stereomutation of a 1,2,3-triketone: an example of an asymmetric reaction
- 15 January 1976
- journal article
- Published by Canadian Science Publishing in Canadian Journal of Chemistry
- Vol. 54 (2) , 210-217
- https://doi.org/10.1139/v76-033
Abstract
The 1,2,3-triketone PhC(Me)2COCOCOPh has been synthesized from mandelic acid in seven steps. Its proton magnetic resonance spectrum features a sharp six-proton methyl singlet at room temperature which broadens considerably at low temperatures but is not resolved into two peaks at 173 K. Similar dynamic behaviour is observed for the monoketone PhC(Me)2COPh. It is concluded that the barrier to interconversion of enantiomeric tricarbonyl helical conformations is significantly less than 7 kcal/mol. The rotation–rotation surface of the ketodialdehyde HCO—CO—CHO has been computed by the CNDO/2 method; the barrier to stereomutation of enantiomeric helical conformations of this tricarbonyl system is found to be 3.9 kcal/mol. The dynamics of this process are discussed in terms of a recently proposed definition of symmetric and asymmetric reactions.Keywords
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