title: Asymmetric Addition of Cyanide to β-Nitroalkenes Catalysed by Chiral Salen Complexes of Titanium(IV) and Vanadium(V).
abstract: Structurally well-defined bimetallic titanium(IV) (salen) and monometallic vanadium(V) (salen) complexes have been used as catalysts for the asymmetric addition of trimethylsilyl cyanide to β-nitroalkenes to produce chiral nitronitriles witheevalues in the range of 79-89 % and conversions up to 100 % at 0 °C. The reaction conditions (solvent, temperature, time and vanadium complex counter-ion) were optimised, and it was shown that the catalyst loading could be significantly reduced (20 to 2 mol %) and the reaction temperature increased (-40 to 0 °C) compared to previous studies that used an in situ prepared catalyst. The results are compared and contrasted with previous results obtained by using the same catalysts for the asymmetric addition of trimethylsilyl cyanide to aldehydes, and a transition-state structure for the asymmetric addition of trimethylsilyl cyanide to nitroalkenes is proposed to account for the observed stereochemistry.
authors.affiliation: School of Chemistry, Newcastle University Bedson Building, Newcastle upon Tyne, NE1 7RU (UK).
authors.forename: Michael
authors.initials: M
authors.lastname: North
authors.forename: James M
authors.initials: JM
authors.lastname: Watson
keywords: Michael addition; N,O ligands; asymmetric catalysis; titanium; vanadium