Rhodium‐Catalyzed Dynamic Kinetic Asymmetric Transformations of Racemic Allenes by the [3+2] Annulation of Aryl Ketimines

Abstract

Racemisierung erforderlich: Eine Rhodium(I)‐katalysierte C‐H‐Aktivierung, die von ungeschützten Ketiminen dirigiert wird, führt zu einer selektiven [3+2]‐Cycloaddition mit Allenen und eröffnet einen Zugang zu hoch substituierten Indenylaminen. Die Reaktion verläuft über eine dynamisch‐kinetische asymmetrische Umsetzung von racemischen Allenen. Der Katalysator kontrolliert sowohl die Enantio‐ und Diastereoselektivität als auch die Regioselektivitäten der C‐H‐Aktivierung und des Allen‐Einbaus sowie das E/Z‐Verhältnis.

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

“…The 1 H NMR spectrum (263 K) of the reaction after five minutes reaction at room temperature showed a major rhodium hydride species at δ =−14.17 ppm ( 1 J Rh‐H =14.0 Hz), which indicates the oxidative addition of the NH bond of benzotriazole to the rhodium center 15a. The subsequent addition of cyclohexylallene to the mixture at −40 °C led to immediate consumption (a few seconds) of the Rh‐H species, which suggests hydrometalation of Rh‐H to cyclohexylallene 15b–d. Warming the mixture to room temperature led to the formation of the coupling product 2 a in 83 % yield ( N 2 / N x >99:1) 12…”

Advances in Stereoconvergent Catalysis from 2005 to 2015: Transition-Metal-Mediated Stereoablative Reactions, Dynamic Kinetic Resolutions, and Dynamic Kinetic Asymmetric Transformations

“…205 The Rh(I)-BINAP ( 88 , Figure 6) catalyzed transformation can tolerate a broad substrate scope using readily available precursors. Importantly, the good to excellent chemical yield, enantio- and diastereoselectivity obtained makes this technology a particularly attractive route to access complex scaffolds.…”

Asymmetric synthesis of N-allylic indoles via regio- and enantioselective allylation of aryl hydrazines

“…The oxidative addition step favours the formation of intermediate A because of the higher acidity of N–H bond of N 1 than N 2 . Hydrometalation of the less-substituted double bond could generate π-allyl-Rh (or δ-allyl-Rh) complex B (or B′ ) 42 43 44 45 , which could generate the desired branched N -allylic aryl hydrazine 1a via reductive elimination. The N -selectivity was determined within the oxidative addition step 46 .…”