A simple, efficient synthesis is reported for (-)-cis- a- and (-)-cis-g-irone, two precious constituents of iris oils, in > 99 % diastereomeric and enantioselective ratios. The two routes diverge from a common intermediate prepared from (-)-epoxygeraniol. Of general interest in this approach is the installation of the enone moiety of irones through a NHC-AuI-catalyzed Meyer–Schuster-like rearrangement of a propargylic benzoate and the use of Wilkinson’s catalyst for the stereoselective hydrogenation of a prostereogenic exocyclic double bond to secure the critical cis stereochemistry of the alkyl groups at C2 and C6 of the irones. The ste- reochemical aspects of this reaction are rationally supported by DFT calculation of the conformers of the substrates un- dergoing the hydrogenation and by a modeling study of the geometry of the rhodium h2 complexes involved in the dia- stereodifferentiation of the double bond faces. Thus, compu- tational investigation of the h2 intermediates formed in the catalytic cycle of prostereogenic alkene hydrogenation by using Wilkinson’s catalyst could be highly predictive of the stereochemistry of the products.

Enantioselective Divergent Synthesis of (−)-cis-α- and (−)-cis-γ-Irone by Using Wilkinson’s Catalyst

BUGONI, SERENA;PORTA, ALESSIO;ZANONI, GIUSEPPE
Conceptualization
;
VIDARI, GIOVANNI
2015-01-01

Abstract

A simple, efficient synthesis is reported for (-)-cis- a- and (-)-cis-g-irone, two precious constituents of iris oils, in > 99 % diastereomeric and enantioselective ratios. The two routes diverge from a common intermediate prepared from (-)-epoxygeraniol. Of general interest in this approach is the installation of the enone moiety of irones through a NHC-AuI-catalyzed Meyer–Schuster-like rearrangement of a propargylic benzoate and the use of Wilkinson’s catalyst for the stereoselective hydrogenation of a prostereogenic exocyclic double bond to secure the critical cis stereochemistry of the alkyl groups at C2 and C6 of the irones. The ste- reochemical aspects of this reaction are rationally supported by DFT calculation of the conformers of the substrates un- dergoing the hydrogenation and by a modeling study of the geometry of the rhodium h2 complexes involved in the dia- stereodifferentiation of the double bond faces. Thus, compu- tational investigation of the h2 intermediates formed in the catalytic cycle of prostereogenic alkene hydrogenation by using Wilkinson’s catalyst could be highly predictive of the stereochemistry of the products.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11571/959434
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