Asymmetric Friedel–Crafts Alkylation of Indoles with Nitrodienes and 2‐Propargyloxy‐β‐nitrostyrenes Catalyzed by Diphenylamine‐Linked Bis(oxazoline)–Zn­(OTf)2 Complexes

Abstract

AbstractThe catalytic asymmetric Friedel–Crafts reaction of indoles with nitrodienes and 2‐propargyloxy‐β‐nitrostyrenes was systematically investigated with diphenylamine‐linked bis(oxazoline)–Zn(OTf)2 complexes. Moderate to good enantioselectivities were obtained with both kinds of substrates (up to 89 % ee for nitrodienes and up to 93 % ee for β‐nitrostyrene derivatives). Further transformation of the corresponding Friedel–Crafts alkylation product of indole with 2‐propargyloxy‐β‐nitrostyrene was carried out to give the chiral isoxazolobenzoxepane derivative, which is of medicinal chemistry interest, with retained enantiomeric purity.