Advertisement

If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.

ENJOY UNLIMITED ACCES TO C&EN

Synthesis

Chiral Lewis acid catalyzes asymmetric photocycloaddition

Reaction takes place through triplet energy transfer instead of photoinduced electron transfer

by Bethany Halford
December 19, 2016 | A version of this story appeared in Volume 94, Issue 49

Being able to control the stereochemistry of organic reactions is important when making certain molecules, such as drug candidates or natural products. Although photochemistry allows chemists to create structural elements that are difficult to access in other ways, such as cyclobutanes, it can be tough to do photochemical reactions enantio­selectively. Chemists at the University of Wisconsin, Madison, led by Tehshik P. Yoon now report an asymmetric [2 + 2] photocycloaddition of 2′-hydroxychalcones (Science 2016, DOI: 10.1126/science.aai8228). The reaction uses tris(bipyridyl) ruthenium(II) as a sensitizer and a chiral Lewis acid to catalyze the reaction (example shown). The chiral Lewis acid serves to dramatically lower the triplet energy state of the chalcone substrate. “This is an energy-transfer reaction instead of a photoredox reaction,” Yoon explains. The Wisconsin chemists expect this approach will help others apply a “detailed understanding of chiral Lewis acid catalysis to stereocontrol in reactions involving electronically excited states,” they write in their report.

Article:

This article has been sent to the following recipient:

0 /1 FREE ARTICLES LEFT THIS MONTH Remaining
Chemistry matters. Join us to get the news you need.