A Mechanistic Analysis of the Palladium‐Catalyzed Formation of Branched Allylic Amines Reveals the Origin of the Regio‐ and Enantioselectivity through a Unique Inner‐Sphere Pathway. (9th September 2019)

• Record Type: Journal Article
• Authors: Hu, Lingfei; Cai, Aijie; Wu, Zhenzhen; Kleij, Arjan W.; Huang, Genping
• Is Part Of: Angewandte Chemie. Volume 131:Number 41(2019)
• Page Start: 14836
• Page End: 14844
• Publication Date: 2019-09-09
• Subjects: Allylische Substitution -- DFT-Rechnungen -- Enantioselektivität -- Innensphären-Mechanismus -- Palladium; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201907375
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: A recently reported palladium‐catalyzed allylic substitution of vinyl‐substituted cyclic carbonates (VCCs) with aryl amines represents a rare example of a regio‐ and enantioselective synthesis of α, α‐disubstituted allylic N ‐aryl amines. However, the underlying reasons for this unusual selectivity profile remain elusive. In the present work, density functional theory (DFT) calculations in combination with mechanistic control experiments were performed to elucidate in detail this allylic amination manifold and the origin of the regio‐ and enantioselectivity. The combined data show that after oxidative addition of the VCC to Pd 0, the nucleophilic attack via an originally proposed outer‐sphere pathway gives, however, the opposite regioisomer compared to the experimental results. Instead, nucleophilic attack of the amine reagent via a unique type of chelation‐assisted, inner‐sphere pathway accounts for the experimentally observed "branched" regioselectivity and high enantio‐control. Abstract : Ein einzigartiger, chelatunterstützter Innensphären‐Mechanismus der Pd‐katalysierten Allylaminierung von cyclischen Vinylcarbonaten mit Arylaminen wurde durch DFT‐Rechnungen und Experimente aufgezeigt. Ein Chelateffekt, der durch eine η 2 ‐Koordination der N‐Arylgruppe mit dem Pd‐Zentrum ermöglicht wird, wurde als Schlüsselinteraktion mit entscheidender Auswirkung auf die Selektivitätsparameter identifiziert.