Selective monoprotection of 1,n-terminal Diols in supercritical carbon dioxide: a striking example of solvent tunable desymmetrization

Peter Licence; William K Gray; Maia Sokolova; Martyn Poliakoff

doi:10.1021/ja044814h

Selective monoprotection of 1,n-terminal Diols in supercritical carbon dioxide: a striking example of solvent tunable desymmetrization

J Am Chem Soc. 2005 Jan 12;127(1):293-8. doi: 10.1021/ja044814h.

Authors

Peter Licence¹, William K Gray, Maia Sokolova, Martyn Poliakoff

Affiliation

¹ School of Chemistry, The University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom.

PMID: 15631478
DOI: 10.1021/ja044814h

Abstract

The reaction between 1,n-terminal diols (n = 3 or 6) with simple alcohols (MeOH, EtOH, and n-PrOH) in supercritical CO(2) over an acid catalyst (Amberlyst 15) leads to two possible products, a mono- and a bis-ether. At 150 degrees C, the selectivity of the reaction with 1,6-hexanediol and MeOH can be switched from 1:20 in favor of the bis-ether at 50 bar to 9:1 in favor of the desymmetrized mono-ether at 200 bar. It is demonstrated that the switch in selectivity is associated with the phase state of the reaction mixture, with monophasic conditions favoring the mono-ether and biphasic conditions favoring the bis-ether. A rationalization of this effect is also presented.