Hamilton JY, Sarlah D, Carreira EM * ETH Zürich, Switzerland
Iridium-Catalyzed Enantioselective Allyl–Alkene Coupling.
J. Am. Chem. Soc. 2014;
136: 3006-3009
Key words
iridium - allyl–alkene coupling - phosphoramidites
Significance
The enantioselective allylic alkylation serves as a reliable route to access useful
enantioenriched building blocks. One particularly important variant is the asymmetric
allylic allylation reaction. The rare reports of this transformation have only utilized
allyl metals (or metalloid species), which lead to the production of stoichiometric
waste. This report signifies an important advance in the field by coupling unactivated
allylic alcohols and alkene nucleophiles with water as the only byproduct.
Comment
The authors present an efficient protocol for a highly asymmetric iridium-catalyzed
allyl–alkene coupling of racemic allylic alcohols and alkenes using the chiral (P,olefin)
phosphoramidite ligand (R)-L1
. In addition, unsymmetrical sulfonamide A1
was found to be the ideal promoter. The reaction, which resembles an ene reaction,
produces chiral 1,5-dienes with high levels of asymmetric induction, and low levels
of product olefin isomerization. The utility of this reaction was exhibited by the
application to a concise synthesis of JNJ-40418677.
