AI Article Synopsis
- * This catalyst operates through a Lewis acid mechanism, leading to the formation of an intermediate called an oxaphosphetane under low-temperature conditions before producing the alkene product upon heating.
- * Computational studies reveal that the reaction occurs in steps, with an initial enantiodetermining addition that forms a potassium betaine complex as a key intermediate.
Article Abstract
We report asymmetric potassium-isothiourea-boronate-catalyzed Wittig olefinations of 4-substituted cyclohexanones with non-stabilized phosphorus ylides to afford highly enantioenriched axially chiral alkenes. The optimal catalyst features an unusual macrocyclic amide-potassium-boronate chelate. Kinetic and spectroscopic analyses are consistent with a Lewis acid mechanism for the catalytic olefination that results in the formation of the oxaphosphetane adduct under cryogenic conditions. Thermal fragmentation of the oxaphosphetane to the alkene product occurs after the reaction is complete. Computational studies indicate that cycloaddition proceeds via a stepwise mechanism involving enantiodetermining polar 1,2-addition to afford an intermediate potassium betaine complex.
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| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC11001253 | PMC |
| http://dx.doi.org/10.1021/jacs.4c00564 | DOI Listing |
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