I have been away a lot – first at the Gordon Conference on the Chemistry and Biology of Peptides (Ventura, California) and then at the Royal Society of Chemistry’s Editors Meeting in London, UK. Now I am finally back and have some time to write.
I want to talk about unusual enolates today. The one implicated in Haufe’s anti-selective aldol reaction that was captured in his recent Org. Lett. publication is as good as it gets. There are many people who are interested in the SF5 group these days. There are myriad reasons for this surge and I mentioned some of them in the past, particularly the materials science angle. Haufe’s work suggests that ester enolates that contain an SF5 substituent are subject to some fairly reliable aldol chemistry, which is interesting because this represents a nice way to “plug” SF5 into a chiral, sp3-rich environment. Up until now I have mainly seen the “aromatic” aspects of SF5.
The starting ester used by Haufe is prepared on scale using a really cool reaction between SF5Cl and a ketene. This process has been known since the 70’s, so check it out (reference 16 in Haufe’s Org. Lett.). I should mention that Professor Haufe of the University of Müenster is no stranger to fascinating transformations of organofluorine compounds. He has been at it for a number of years and is currently one of the Regional Editors of the Journal of Fluorine Chemistry.