Hashimoto T, Kawamata Y, Maruoka K * Kyoto University, Japan
An Organic Thiyl Radical Catalyst for Enantioselective Cyclization.
Nature Chem. 2014;
6: 702-705
Key words
rational catalyst design - thiyl radical - radical cyclization
Significance
Maruoka and co-workers report an enantioselective radical cyclization catalyzed by
the newly designed thiyl radical catalyst B. The reaction starts from acceptor-substituted vinyl cyclopropanes 1, which are opened by the catalyst and reclose to cyclopentane 2 after addition to a vinyl ether. Based on the low selectivity obtained with catalyst
A and the transition state model with two quadrants available for the formation of
opposite enantiomers, catalyst B was designed blocking of the quadrants and enabling high enantioselectivities.
Comment
Through rational catalyst design, the Maruoka group has achieved the first highly
stereoselective C–C bond formation using a thiyl radical catalyst. This proof of principle
is expected to spur further research towards the application of catalysts similar
to B and the development of novel thiyl radical catalysts with innovative chiral backbones.
Further research is also expected to address the currently poor diastereocontrol between
a possible stereocenter at C1 and the anti-configured stereodiad at C3 and C4.
