213550-05-1Relevant academic research and scientific papers
Silica-catalysed and highly stereoselective convergent and nonconvergent rearrangements of menthone enol acetate epoxides: Easy access to the four α-hydroxymenthone stereoisomers
Tranchimand, Sylvain,Faure, Bruno,Naubron, Jean-Valere,Alphand, Veronique,Archelas, Alain,Iacazio, Gilles
, p. 4365 - 4372 (2012)
During a program dedicated to the biocatalytic access of structurally useful α-hydroxy ketones, we made the unexpected observation that epoxy enol acetates derived from (+)- and (-)-menthone stereoselectively rearranged on exposure to silica through a diastereoselective process, providing easy access to the complete set of α-hydroxymenthone stereoisomers. The absolute configurations of the four stereoisomers were unambiguously established by IR-VCD and X-ray diffraction, thus clarifying some literature discrepancy. Two of the four stereoisomers could also be obtained through astereoconvergent process, thus avoiding the inherent 50 % yield limitations of such diastereoselective reactions. A solvent-free version allowing an extremely rapid reaction ( 2 h) is also described. Finally, the observed diastereoselection was investigated by DFT calculations. Epoxy enol acetates derived from menthone unexpectedly rearranged diastereoselectively on exposure to silica, giving easy access to the complete set of α-hydroxymenthone stereoisomers. Two of the four stereoisomers were also available through a diastereoconvergent process. Finally, the observed stereoselection was investigated by DFT calculations. Copyright
