title: Selective monoprotection of 1,n-terminal Diols in supercritical carbon dioxide: a striking example of solvent tunable desymmetrization.
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.
authors.affiliation: School of Chemistry, The University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom.
authors.forename: Peter
authors.initials: P
authors.lastname: Licence
authors.forename: William K
authors.initials: WK
authors.lastname: Gray
authors.forename: Maia
authors.initials: M
authors.lastname: Sokolova
authors.forename: Martyn
authors.initials: M
authors.lastname: Poliakoff