Montgomery TP, Hassan A, Park BY, Krische MJ * University of Texas at Austin, USA
Enantioselective Conversion of Primary Alcohols to α-
exo-Methylene γ-Butyrolactones via Iridium-Catalyzed C–C Bond-Forming Transfer Hydrogenation:
2-(Alkoxycarbonyl)allylation.
J. Am. Chem. Soc. 2012;
134: 11100-11103
Key words
iridium - transfer hydrogenation
Significance
In this paper, the authors report the first example of catalytic enantioselective
carbonyl 2-(alkoxycarbonyl)allylation via iridium-catalyzed transfer hydrogenative
carbon–carbon bond coupling of acrylic ester to alcohols. The desired product was
obtained with good yields and enantioselectivities. The synthetic application of this
method was also illustrated by rapidly converting the adduct into disubstituted α-exo-methylene γ-butyrolactone diastereoselectively.
Comment
Previously, Krische’s research on the iridium-catalyzed enantioselective carbonyl
allylation was restricted to mono-substituted olefins as late transition metal–olefin
π complexes become less stable with higher degrees of olefin substitution. However,
the authors recently reported that the improved π-backbonding of carboxy substituents
compensates the above-mentioned destabilization and therefore expanded their research
to vinylogous aldol additions as well as the utilization of acrylic ester as 2-(alkoxycarbonyl)allylmetal
equivalents.
