Catalytic enantioselective synthesis of oxazolines with vinylogous isocyano esters

Vinylogous isocyano esters have been prepared for the first time. They react with aldehydes to give chiral oxazolines bearing a pendant conjugated ester under synergistic silver/organocatalysis. The reaction is carried out using a bifunctional squaramide in combination with silver oxide and performs well with a number of aryl-, heteroaryl-, and cycloalkyl aldehydes, providing the expected heterocycles in good yields with good diastereoselectivity and enantiomeric excesses ranging from 60% to 95% ee. All new compounds have been characterized by NMR and other spectroscopic techniques. Raw NMR data (fid) for all new compounds prepared in this work are provided in the data set.

Methods
NMR spectra were recorded using a Bruker Avance III 300 or Bruker Neo500 at, respectively, 300 MHz, or 500 MHz for 1H, or 75 MHz, or 125 MHz for 13C and were processed using MestreNova software.