Lewis Acid Catalyzed Benzylic C−H Bond Functionalization of Azaarenes: Addition to Enones

Abstract

A Lewis acid catalyzed benzylic C-H bond functionalization of alkyl-substituted azaarenes is described. Sc(OTf)(3) and Y(OTf)(3) promoted the direct addition of alkyl-substituted azaarenes and benzoxazole to enones and an α,β-unsaturated N-acylpyrrole. Products were obtained in 60-96% yield.

Diastereo- and Enantioselective Pd(II)-Catalyzed Additions of 2-Alkylazaarenes to N-Boc Imines and Nitroalkenes

“…12 Also of relevance are racemic Sc(III)-catalyzed Michael additions of alkylazaarenes to enones and an α,β-unsaturated pyrrole, 11,13 and Yb(III)-catalyzed Michael additions of alkylazaarenes to alkylidine malononitriles. 14 While these reports demonstrate important proof of concept, the low acidity of alkylazaarenes means that high temperatures are often required, which may hinder the development of enantioselective variants.…”

Lewis Acid Promoted Benzylic Cross‐Couplings of Pyridines with Aryl Bromides

“…The beneficial effect of Lewis acids in the additions of 2-picoline to imines and enones has already been demonstrated. [10,11] Thus, we directed our attention toward the use of bases (Met-base) bearing a Lewis acidic metal center for the metalation. Recently, we have reported a kinetically highly active LiCl-solubilized TMP base (TMP = 2,2,6,6-tetramethylpiperidyl): TMPZnCl·LiCl (7) displays high chemoselectivity in various directed zincations of arenes and heterocycles.…”

Lewis‐Säure‐vermittelte benzylische Kreuzkupplungen von Pyridinen mit Arylbromiden

“…Der positive Effekt von Lewis-Säuren auf die Addition von 2-Picolin an Imine und Enone wurde bereits demonstriert. [10,11] Daher haben wir unsere Aufmerksamkeit auf die Verwendung von Basen (Met-Base) gerichtet, die ein Lewis-saures Metallzentrum enthalten, um eine Metallierung durchzuführen. Kürzlich haben wir über eine kinetisch hoch aktive LiCl-komplexierte TMP-Base (TMP = 2,2,6,6-Tetramethylpiperidin) berichtet: TMPZnCl·LiCl (7) zeigt eine hohe Chemoselektivität in verschiedenen direkten Zinkierungen von Arenen und Heterocyclen.…”