Journal Publications

Simon Doherty, Julian G. Knight, Catherine H. Smyth, Ross W. Harrington, and William Clegg, J. Org. Chem, 2006, 71, 9751.

Abstract: A comparative study of the carbonyl-ene reaction between a range of 1,1^/-disubstituted or trisubstituted alkenes and ethyl trifluoropyruvate catalyzed by Lewis acid platinum group metal complexes of the type [M{(R)-BINAP}]²⁺ (M = Pt, Pd, Ni) revealed subtle but significant differences in their reactivity. For instance, the palladium based Lewis acid [Pd{(R)-BINAP}]²⁺ catalyzes the ene reaction between methylene cycloalkane to afford the expected a-hydroxy ester in good yield and excellent diastereo- and enantioselectivity. In contrast, under the same conditions the corresponding [M{(R)-BINAP}]²⁺ (M = Pt, Ni) catalyzes isomerization of methylene cycloalkane and the ene reaction of the resulting mixture of methylene cycloalkane and 1-methylcycloalkene at similar rates to afford a range of a-hydroxy esters in high regioselectivity, good diastereoselectivity and good to excellent enantioselectivity. In addition, [Pt{(R)-BINAP}]²⁺ also catalyzes post-reaction isomerization of the ene product as well as a consecutive ene reactions to afford a double carbonyl-ene product. The sense of asymmetric induction has been established by single-crystal X-ray crystallography and a stereochemical model consistent with the formation of (S)-configured a-hydroxy ester has been proposed; the same model also accounts for the observed exo-diastereoselectivity as well as the level of diastereoselectivity.