Probing the efficiency of N-heterocyclic carbene promoted O- to C-carboxyl transfer of oxazolyl carbonates.
Screening of a range of azolium salts, bases and solvents for reactivity indicates that triazolinylidenes, generated in situ with KHMDS in THF, promote the Steglich rearrangement of oxazolyl carbonates with high catalytic efficiency (typical reaction time 5 min at <1.5 mol % NHC). This protocol shows wide substrate applicability, even allowing the efficient generation of vicinal quaternary centers. An improved experimental procedure is also described that allows a simplified one-pot reaction protocol to be employed with similarly high catalytic efficiency.
Thomson
Jennifer E
JE
EaStCHEM, School of Chemistry, University of St. Andrews, North Haugh, St. Andrews KY16 9ST, U.K.
Campbell
Craig D
CD
Concellón
Carmen
C
Duguet
Nicolas
N
Rix
Kathryn
K
Slawin
Alexandra M Z
AM
Smith
Andrew D
AD