Unusual highly regioselective direct aldol additions with a moisture-resistant and highly efficient titanium catalyst.
[reaction: see text] The extremely robust and water-stable tetranuclear complex Ti(4)(mu-BINOLato)(6)(mu(3)-OH)(4) was found to catalyze the direct aldol addition with high regioselectivities at the more steric alpha-encumbered side of unsymmetrical ketones. As few as 0.2 mol % loadings with this cluster were enough to afford complete conversions. The reaction proceeds very smoothly without a significant amount of byproducts. The formation of quaternary stereocenters is described.
Mahrwald
Rainer
R
Humboldt-Universität zu Berlin, Institut für Chemie, Germany. rainer.mahrwald@rz.hu-berlin.de
Schetter
Bernd
B