Ever since my lab identified aziridine aldehyde dimers in 2006 and termed them “kinetically amphoteric molecules”, we have been searching for new examples of this privileged, yet strange, class of compounds. Of course, we have also paid close attention to other researchers’ efforts in uncovering cases of amphoteric reactivity!

I have been really intrigued by Professor Sun’s oxetane aldehydes. Here is an example of an efficient [6+2] cyclization with siloxy alkynes giving rise to the first intermolecular synthesis of eight-membered lactones.

http://onlinelibrary.wiley.com/doi/10.1002/anie.201200513/abstract

There are two pathways (a and b) that are being considered by the authors:

Drawing on their initial discovery, Sun and co-workers later expanded the utility of oxetane aldehydes to multicomponent reactions. Thus, the oxetane ring was shown to be a superb directing group that played a crucial role in achieving both high yields and high enantioselectivities in amphoteric molecule-driven multicomponent reactions. I will continue paying attention to advances in this area…