Highly Enantioselective Direct Michael Addition of 1H‐Benzotriazole to Chalcones Catalyzed by Sc(OTf)₃/N,N′‐Dioxide Complex

Abstract

The N,N′‐dioxide–Sc(OTf)3 complex was applied in the asymmetric Michael reaction of 1H‐benzotriazole with chalcones to give the corresponding N‐1 products in excellent yields (up to 99 %) with excellent enantioselectivities (up to 99 % ee). Further transformation into other optically active derivatives such as β‐benzotriazolyl ester, alcohol, and amide were also realized with excellent results.

Recent Advances in Metal-Catalyzed Asymmetric 1,4-Conjugate Addition (ACA) of Nonorganometallic Nucleophiles

“…Sc­(III) complexes based on chiral N,N′ -dioxide ligands were also demonstrated to be highly efficient catalysts in a series of aza-Michael reactions (Scheme ). ,− For instance, using chalcones as the Michael acceptors, the asymmetric addition of benzoyl hydrazide was carried out in the presence of complex L21c –Sc­(OTf) 3 , giving the addition products in acceptable yields with good enantiocontrol (up to 97% ee; Scheme a) . Later, the application of this catalyst system was extended to the addition of pyrazoles to α-aryl-substituted vinyl ketones using ScCl 3 as metal source and L22c as ligand (up to 99% yield and 94% ee; Scheme b) .…”

“…Later, the application of this catalyst system was extended to the addition of pyrazoles to α-aryl-substituted vinyl ketones using ScCl 3 as metal source and L22c as ligand (up to 99% yield and 94% ee; Scheme b) . The addition of 1H-benzotriazole to chalcones was realized by employing complex L22h –Sc­(OTf) 3 as the catalyst (Scheme c) . The bromoamination of α,β-unsaturated aromatic ketones was achieved with particularly good outcomes in the presence of 0.05 mol % of L22i –Sc­(OTf) 3 (up to 99% yield, 99% ee, and 99:1 dr; Scheme d) .…”

“…404 The addition of 1H-benzotriazole to chalcones was realized by employing complex L22h−Sc(OTf) 3 as the catalyst (Scheme 98c). 403 The bromoamination of α,β-unsaturated aromatic ketones was achieved with particularly good outcomes in the presence of 0.05 mol % of L22i−Sc(OTf) 3 (up to 99% yield, 99% ee, and 99:1 dr; Scheme 98d). 86 On the basis of a mechanistic study, a chiral-bromonium-based mechanism and transition state were proposed by the authors.…”

Indium(III) Triflate-Catalyzed Reactions of Aza-Michael Adducts of Chalcones with Aromatic Amines: Retro-Michael Addition versus Quinoline Formation

“…Apart from α,β-unsaturated aldehydes and methyl ketones, no other α,β-unsaturated carbonyl compounds (such as chalcones) could be employed in the synthesis, and this surprising fact stimulated us to investigate the reason behind it. As the direct quinoline synthesis from aromatic amines and chalcones at the best stops at the aza-Michael adduct stage, we prepared the aza-Michael adducts independently and subjected them to further cyclization. We found that the Michael adducts derived from substituted anilines and chalcones underwent retro-Michael addition to give the original starting materials, whereas the adducts derived from 1-naphthylamine and chalcones afforded the expected quinoline derivatives in good yields.…”

Cobalt-Catalyzed Carbonylative Cross-Coupling of Alkyl Tosylates and Dienes: Stereospecific Synthesis of Dienones at Low Pressure

“…Additionally, applications of the product dienones in selective 1,4- or 1,6-conjugate additions, or Diels-Alder cycloadditions, are easily envisioned. 11 …”