Nazarov cyclizations are catalyzed by a dicationic Ni(II) complex containing the chiral tridentate phosphine Pigiphos; the catalyst exerts a high degree of torquoselectivity and affords the products in up to 88% ee.

Vanadium(IV) species generated in situ from V(salen)Cl2 complexes (1) by reaction with 2 equiv. of AgSbF6 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 electron‐donating group at position 1 of the 1,4‐dien‐3‐one system.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

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Enantioselective syntheses O 0031Ni (II)-Catalyzed Enantioselective Nazarov Cyclizations. -Dicationic Ni(II)--PIGIPHOS complexes catalyze Nazarov cyclization reactions to afford the products up to 88% e.e. -(WALZ, I.; TOGNI*, A.; Chem. Commun. (Cambridge) 2008, 36, 4315-4317; Dep. Chem. Appl. Biosci., Swiss Fed. Inst. Technol., ETH, CH-8093 Zuerich, Switz.; Eng.) -D. Singer 06-027

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