Iodine Wonder

Quaternary Ammonium (Hypo)iodite Catalysis for Enantioselective Oxidative Cycloetherification
Muhammet Uyanik, Hiroaki Okamoto, Takeshi Yasui, and Kazuaki Ishihara
Science 11 June 2010 328: 1376-1379

Also featured in:
C & EN June 14, 2010 Volume 88, Number 24 p. 11
Iodine Catalysis Goes Green
Sarah Everts
http://pubs.acs.org/cen/news/88/i24/8824notw4.html

^o^: If a synthetic chemistry article is on the SCIENCE magazine, it has got to be great! It should come as no surprise, given that iodine reagents (espc. hypervalent iodine, the 'cationic' types - meaning those with positive oxidation states) are emerging as rising stars in synthetic chemistry, and often catalysis can be done METAL-FREE and in a GREEN (environmental friendly) way - an achievement in organocatalysis. Yet this time, the iodine fella is an ANIONIC (-ve charge) iodite rather than a positive-charged one. The philosophy behind this catalytic strategy is that the authors are playing with the oxidation states of the iodine species to effect the oxidative cyclization reactions. Indeed, from their screening studies the cationic iodine species (e.g. the hypervalent ones) afford 'messy' results (the way the authors put it in the article) and it is the 'I minus' that does all the magic here. Do not divert our focus, however, from its positive charge partner in crime, the quaternary ammonium salt, as it is the one which provides the products with impressive enantioselectivities. The co-oxidant is the common hydrogen peroxide (H2O2) and the reactions are carried out in a mixture of organic solvent and WATER - likely due to the 'greasiness' of the substrates, and the authors can possibly push it forward to a greener process. Overall an intriguing reaction with an iodite salt - yet another great contribution to green chemistry. And don't forget the reaction is ATOM-ECONOMICAL too.

by Ed Law 14/06/2010