Erste Röntgenstrukturanalysen von Rhodium(III)‐η¹‐Allyl‐Komplexen und ein plausibler Mechanismus für allylische Isomerisierungsreaktionen

Abstract

Allyltransfer von Metall zu Metall: Anhand der ersten strukturell charakterisierten Rh(η1‐allyl)‐Komplexe wird gezeigt, dass der σ‐gebundene Allylsubstituent von einem RhIII‐ auf einen RhI‐Komplex im schnellen Gleichgewicht übertragen werden kann. Dies könnte die Abnahme der Regioselektivität in Rh‐katalysierten allylischen Alkylierungen erklären, für die Komplex 1 ein aktiver Katalysator ist.

Biosensing Applications of V2O5‐CeO2 Mesoporous Silica

“…Hydrometalation of the more‐substituted double bond could generate the σ‐ or π‐allyl/Rh complex C , which could generate the desired branched N‐allylic heterocyles by reductive elimination (or external benzimidazole attack). The regioselectivity of this step is in accordance with that observed previously for other allylrhodium complexes 18b–d. The palladium‐catalyzed reactions may follow a similar mechanism, but the reductive elimination (or external attack) step favors the less hindered position and thus affords the linear product 19.…”

Unlocking the N2 Selectivity of Benzotriazoles: Regiodivergent and Highly Selective Coupling of Benzotriazoles with Allenes

“…Oxidative addition of the tautomers ( A or A ′) of benzotriazole to Rh I generates a Rh III complex ( B or B ′) 15a. Hydrometalation of the less‐substituted double bond could generate a σ‐allyl‐Rh complex ( C or C ′),15e–g which could generate the desired branched N ‐allylic benzotriazoles on reductive elimination 16. The N selectivity is dictated by the energy difference between the two catalytic cycles: the N 2 ‐selective product is formed via A ‐ B ‐ C , and the N 1 ‐selective product is produced via A ′‐ B ′‐ C ′.…”

Non‐Directed Cross‐Dehydrogenative (Hetero)arylation of Allylic C(sp3)−H bonds enabled by C−H Activation

“…Based on these results two crucial hypotheses can be postulated:f irst, aH eck-type carbometalation pathway can be excluded [12b] and therefore second, the generation of either a p-(h 3 )-allyl, a s-(h 3 )-allyl or a s-(h 1 )allyl species can be proposed in the reaction medium (Scheme 4b). [16] Although these species can undergo a s-ps-isomerization [16,17] we then attempted to isolate one of these proposed intermediates.Pleasingly,wewere indeed successful in isolating aR h-p-allyl complex (3fa)f rom CÀHa ctivation conditions when 2-allylnaphthalene was employed (Scheme 4c). Thes olid-state structure of the complex was confirmed by X-ray crystallography showing that a h 3 -p-allylcomplex was obtained.…”