ASAP Thursday

Some good papers have shown up on ASAP this week. Here's two that rose to the top for me.

First is a contribution from Shu Kobayashi with some very interesting chemistry using chiral Calcium complexes. The reaction he investigated was the Michael addition of glycine derivatives with acrylates. He showed the importance of an enolizable proton on the bis-oxazoline ligand and suggests that the reactive species is a calcium Brønsted base. This generates a chiral calcium enolate that undergoes Michael addition to the acceptor. Subsequently, an intramolecular Mannich reaction ensues to afford pyrrolidines in very high selectivity.

Susumu Saito, Tetsu Tsubogo, and Shu Kobayahsi, JACS, DOI: 10.1021/ja0709730

Organocatalysis is all the rage now, and even we are trying our hand at some. Xiao has just reported a slightly new twist on organocatalysis by carrying out an intramolecular Friedel-Crafts reaction with indoles to form tricyclic compounds. Selectivities are are pretty good in some cases.

Chang-Feng Li, Hiu Liu, Jie Liao, Yi-Ju Cao, Xiao-Peng Liu, and Wen-Jing Xiao, OL, DOI: 10.1021/ol0703130