Lewis‐Säure‐vermittelte benzylische Kreuzkupplungen von Pyridinen mit Arylbromiden

Abstract

ZnCl2, Sc(OTf)3 oder BF3⋅OEt2 vermitteln die Pd‐katalysierte Arylierung von Methylpyridinen und ähnlichen Heterocyclen (siehe Beispiel). Die Komplexierung des Stickstoffatoms im Heterocyclus durch die Lewis‐Säure erleichtert die reduktive Eliminierung, was in hohen Ausbeuten zu zahlreichen arylierten Produkten führt. Mit BF3⋅OEt2 gelingt darüber hinaus im Fall des 2,4‐Lutidins eine hoch regioselektive Metallierung.

Mechanistic Study of a Switch in the Regioselectivity of Hydroheteroarylation of Styrene Catalyzed by Bimetallic Ni–Al through CH Activation

“…For example, the groups of Hartwig3a and Nolan3b have reported that Lewis acids such as AlCl 3 and BEt 3 accelerate palladium‐mediated reductive elimination reactions. Knochel reported the direct palladium‐catalyzed arylation of methyl‐substituted pyridine promoted by ZnCl 2 , Sc(OTf) 3 , and BF 3 ⋅ OEt 2 with excellent regioselectivity 3c. Similarly, our group,4 as well as those of Nakao and Hiyama5 and Kanai,6 have observed the beneficial effect of added AlMe 3 in promoting nickel‐mediated CH bond activation of heteroarenes.…”

Benzylic Arylation of 2-Methyl-5-membered Heterocycles Using TMP-Bases

“…In the case of cyano-substituted aryl bromides (5b and 5j), we have found that the addition of 10% Sc(OTf) 3 17 improves the cross-coupling yield. 5,18 The generality of our approach is demonstrated by performing the arylation of other related 5-membered heterocycles such as the 2-methylindole derivative 14 19 and the 2-methylbenzimidazole 15. 20 In these cases, TMPZnCl 3 LiCl (1) proved to be a suitable base, and a complete zincation could be obtained within 1 h at 25 °C.…”

Nickel Complexes Modified by O,N,O’‐Ligands as Synthons for the Straightforward Synthesis of Highly Efficient Precatalysts for CC Bond Formation

“…m.p 145-147 8C. 1 H NMR, 13 Single-crystal X-ray Structure Determination [8] Crystals were each mounted on a glass capillary in perfluorinated oil and measured in a cold N 2 flow. The data were collected on an Oxford Diffraction Xcalibur S Sapphire at 150(2) K (Mo Ka radiation, l = 0.71073 ).…”