Catalytic and enantioselective aza-ene and hetero-Diels–Alder reactions of alkenes and dienes with azodicarboxylates

Abstract

Lewis acids such as Cu(OTf)₂, Zn(OTf)₂, Yb(OTf)₃ and Nd(OTf)₃ catalyze the aza-ene reaction of alkenes with azodicarboxylates, giving the allylic amination adducts. The use of bis(2,2,2-trichloroethyl)azodicarboxylate as the amination reagent and Cu(OTf)₂ and Yb(OTf)₃ as the catalysts gave the aza-ene reaction of different alkenes, leading to the corresponding allyl amines in high yields. Chiral copper complexes prepared from Cu(OTf)₂ and chiral bisoxazoline ligands were found to catalyze the enantioselective aza-ene reaction of azodicarboxylates with alkenes and the hetero-Diels–Alder reaction with cyclopentadiene, giving the corresponding aza-ene- and hetero-Diels–Alder adducts, respectively, in good yields and moderate enantioselectivities.