Synthesis of chiral benzene-based tetraoxazolines and their application in asymmetric Friedel–Crafts alkylation of indole derivatives with nitroalkenes

• A series of new chiral benzene-based tetraoxazoline ligands were prepared.
• The catalytic system is composed of the synthesized tetraoxazoline and ZnCl2.
• The catalytic system was tested in asymmetric Friedel–Crafts alkylations.
• The catalytic system presented excellent activities and enantioselectivities.

A series of new chiral benzene-based tetraoxazoline ligands were prepared in good yields through the reaction of 1,2,4,5-benzenetetracarboxylic acid and chiral β-amino alcohols by continuous removal of water, and the asymmetric Friedel–Crafts alkylation of indole derivatives with nitroalkenes was tested using the chiral catalysts, which were generated in situ by refluxing the above ligands and anhydrous zinc chloride in solvent. In most case, good yields (up to 99%) and excellent enantioselectivities (up to 98% ee) were obtained.

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