Hydroxytetraphenylenes as Chiral Ligands: Application to Asymmetric Darzens Reaction of Diazoacetamide with Aldehydes

Hydroxytetraphenylenes with rigid conformations are potential candidates for employment as chiral ligands in asymmetric synthesis. Highly diastereo- and enantioselective Darzens reactions between aldehydes and diazo-N,N-dimethylacetamide were found to be catalyzed by a chiral titanium complex formed in situ from Ti(O ⁱ Pr)₄ and chiral 1,16-dihydroxytetraphenylene, leading to the formation of cis-glycidic amides in moderate to high yields with excellent enantiomeric purities (40–99% yield, up to 99% ee).