Trost BM, * Ehmke V, O’Keefe BM, Bringley DA. Stanford University, USA
Palladium-Catalyzed Dearomative Trimethylenemethane Cycloaddition Reactions.
J. Am. Chem. Soc. 2014;
136: 8213-8216
Key words
palladium - nitroarenes - trimethylene-methanes - [3+2] cycloaddition
Significance
The authors describe a palladium-catalyzed enantioselective dearomative trimethylenemethane
(TMM) [3+2] cycloaddition with three nitroarenes. Chiral phosphoramidite or diamidophosphites
were utilized to induce moderate to high levels of enantioselectivities along with
high chemical yields. The key significance of this work is the selective tuning of
the reactivity and enantioselectivity of the catalyst system, which enables exclusive
formation of the dearomatized products for an intermolecular cycloaddition in high
enantioselectivities.
Comment
The current catalytic system is unable to induce high levels of enantioselectivities
for the unsubstituted TMM donor in contrast to the alkynyl-substituted TMM donor.
It was proposed that the alkynyl substituent bonds tightly to the β-carbon of the
nitroarene and creates more steric bulk, which enables a higher degree of differentiation
between the two prochiral phases in the transition state.
