Abstract Vanadium (IV) species generated in situ from V (salen) Cl 2 complexes (1) by reaction with 2 equiv. of AgSbF 6 are effective catalysts for Nazarov cyclizations. Thus, dialkenyl ketones bearing α-ester groups are efficiently converted to corresponding cyclopentenones in good yields at room temperature, in the presence of 2 mol-% catalyst. Under such conditions full conversion takes place within minutes for substrates bearing an ...
