N-heterocyclic carbene-mediated enantioselective addition of phenols to unsymmetrical alkylarylketenes
Chiral N-heterocyclic carbenes (NHCs) mediate the enantioselective addition of 2-phenylphenol to unsymmetrical alkylarylketenes, delivering α-alkyl-α-arylacetic acid derivatives with good levels of enantiocontrol (up to 84% ee). Enantiodivergent stereochemical outcomes are observed using 2-phe-nylphenol and benzhydrol in the NHC-promoted esterification reaction using a triazolium precatalyst derived from pyroglutamic acid, consistent with distinct mechanistic pathways operating within these processes.
Concellon, Carmen,Duguet, Nicolas,Smith, Andrew D.
supporting information; experimental part
p. 3001 - 3009
(2010/03/26)
Stereoselective Construction of Acyclic Carbon Chains by a One-Pot Coupling Process Based on Alkenyloxazoline-Titanium Complexes
A versatile organometallic intermediate, an alkenyloxazoline-titanium complex, has been developed that enables one-pot multicomponent diastereoselective and asymmetric coupling processes to be achieved in a remarkably efficient manner (see scheme).