Enantioselective Syn-Selective Scandium-Catalyzed Ene Reactions

Abstract

An enantio- and diastereoselective carbonyl-ene reaction catalyzed by chiral scandium pyridyl bis(oxazoline) (pybox) complexes has been developed. Uniformly high enantiomeric excesses and good yields were observed. Use of trisubstituted olefins generated the syn product in high enantio- and diastereoselectivity.

A multivalent PyBox asterisk ligand

“…The investigation of multivalency in PyBox chemistry is a central concept in this work. It correlates well with recent uses of PyBox ligands in numerous stereoselective reactions: 4 aldol condensation, 5 cyclopropanation, 6 Diels-Alder, 7 hydrosilylation of ketones, 8 alkene epoxidation, 9 1,3-dipolar cycloaddition, 10 ene, 11 Negishi couplings, 12 cyanation, 13 and Friedel-Crafts, 14 etc.…”

Lewis acid-promoted carbonyl addition of 1,3-bis(silyl)propenes

“…Despite the fact that glyoxylamide 3a has been used successfully in asymmetric glyoxylamide-ene reactions, 21 Sakurai allylations, 14 and vinylsilane 11 and propargylsilane 22 additions, it is not commercially available, and has to be prepared via a tedious procedure. 21 Consequently, we were interested to see whether the present reaction protocol could be applied for the addition of silane 1a to commercially available ethyl glyoxylate 3b, thus making it more suitable for future applications. To our delight, increasing the catalyst loading to 30% of SnCl 4 together with a prolonged reaction time afforded allylsilane 4b in 84% yield ( Table 2, entry 2).…”

Hydrogen peroxide-promoted metal free oxidative amidation of 2-oxoaldehydes: a facile access to unsymmetrical oxamides

“…The synthesis method of 2-Oxoaldehyde derivatives 1ae1l were according to the reported procedure. 15 General chemicals were purchased from commercial suppliers and used without further purification.…”