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

Cage-Shaped Borate Catalyst Recognizes Aromatic Aldehydes

Lewis acid catalyst with an enzymelike binding pocket selects aromatic aldehydes over aliphatic aldehydes in Diels-Alder reactions

by Stephen K. Ritter
March 19, 2012 | A version of this story appeared in Volume 90, Issue 12

A boron-based organocatalyst with an enzymelike π-binding pocket has been designed to catch and hold aromatic aldehydes to facilitate Diels-Alder cycloaddition reactions. The research team led by Makoto Yasuda and Akio Baba of Japan’s Osaka University believes this is the first reported example of the molecular recognition of an aromatic aldehyde over an aliphatic aldehyde in a catalytic manner. Yasuda, Baba, and coworkers previously designed cage-shaped triphenylborate Lewis acids, such as B(OC6H4)3CH, that allow them to increase Lewis acidity over planar, open-shaped borate catalysts. The triphenylborate has a shallow binding pocket and reacts nearly equally with aromatic and aliphatic aldehydes, which the team showed in competitive Diels-Alder reactions pitting benzaldehyde against butanal. The researchers have now taken the borate catalysts to a different level by adding aryl groups to the phenyl rings to form B(OC6H3aryl)3CH analogs, such as the naphthyl example shown (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201200346). The additional aryl rings create a deeper pocket and a larger π-aromatic framework for the catalyst to selectively bind aromatic aldehydes. The naphthyl catalyst favors p-cyanobenzaldehyde over butanal at a ratio of up to 27.5:1.

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.