Abstract
The Jacobsen and pybox type ligands effect chiral induction in the presence of niobium(V) chloride and tantalum(V) chloride in the Lewis acid catalysed Diels–Alder reaction.
Highlights
Chiral induction of the Diels–Alder reaction using Lewis acid catalysis in the presence of chiral ligands has met with a great deal of success [1]
Having an interest in chiral Lewis acids based on niobium and tantalum, we decided to investigate the potential for asymmetric induction of the bis-oxazoline and pybox classes of ligand in the presence of niobium(V)chloride or tantalum(V)chloride and compare these results with those of the R,R and S,S Jacobsen ligand (Figure 2)
The Jacobsen ligand has been used in the Lewis acid catalysis of the Diels-Alder reaction in the presence of chromium [6] and aluminium [7], the enantioselective addition of HCN to imines [8], and the enantioselective ring opening of epoxides which has been attributed to both nucleophilic delivery of a Cr-N3 species and Lewis acid catalysis [6, 9]
Summary
Chiral induction of the Diels–Alder reaction using Lewis acid catalysis in the presence of chiral ligands has met with a great deal of success [1]. Having an interest in chiral Lewis acids based on niobium and tantalum, we decided to investigate the potential for asymmetric induction of the bis-oxazoline and pybox classes of ligand in the presence of niobium(V)chloride or tantalum(V)chloride and compare these results with those of the R,R and S,S Jacobsen ligand (Figure 2). The Jacobsen ligand has been used in the Lewis acid catalysis of the Diels-Alder reaction in the presence of chromium [6] and aluminium [7], the enantioselective addition of HCN to imines [8], and the enantioselective ring opening of epoxides which has been attributed to both nucleophilic delivery of a Cr-N3 species and Lewis acid catalysis [6, 9]
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