Mangan‐katalysierte dehydrierende Alkylierung oder α‐Olefinierung von Alkyl‐N‐heteroarenen durch Alkohole

Abstract

Die Katalyse mit auf der Erde häufig vorkommenden Übergangsmetallen ist eine Option, um unsere seltenen Edelmetallressourcen zu schonen, und ist besonders interessant, wenn neue Reaktivitäts-oder Selektivitätsmuster beobachtet werden. Wirberichten hier über eine neue Reaktion:die dehydrierende Alkylierung oder a-Olefinierung von Alkyl-Nheteroarenen mit Alkoholen. In unserem Labor entwickelte Mangankomplexekatalysieren die Reaktion effizient. Fe-und Co-Komplexe,die durch solcheLiganden stabilisiert sind, sind im Wesentlichen inaktiv.W ährend der Reaktion wird Wasserstoff freigesetzt, und funktionelle Gruppen wie Brom, Iod oder Olefine kçnnen toleriert werden. Eine Vielzahl von Alkyl-Nheteroarenen kann funktionalisiert werden, und Benzylalkohole sowie aliphatische Alkohole gehen die Reaktion ein.

Acceptorless Dehydrogenative Coupling Reactions by Manganese Pincer Complexes

“…Among several other catalytic complexes screened, Kempe and co‐workers found that Mn ‐ 20 , having a triazine pincer ligand backbone swiftly catalyzed the α‐olefinations of 2‐methylquinolines and N‐heteroarenes. Notably, the corresponding iron and cobalt complexes tested in this study were found to be inactive under a similar condition [93] …”

“…In 2018, Kempe [93] and co‐workers and Maji [94] and co‐workers independently demonstrated manganese catalyzed olefination reaction of alkyl‐substituted heteroarenes with alcohols (Scheme 44). Among several other catalytic complexes screened, Kempe and co‐workers found that Mn ‐ 20 , having a triazine pincer ligand backbone swiftly catalyzed the α‐olefinations of 2‐methylquinolines and N‐heteroarenes.…”

“…Notably, the corresponding iron and cobalt complexes tested in this study were found to be inactive under a similar condition. [93] The Kempe group found that the dehydrogenative coupling reaction proceeds at a low catalytic loading of Mn-20 (0.5 mol%) with 40 mol% of KOH and a t AmOH/toluene mixture as the solvent at 135 °C (Scheme 44). The yield of the product was quite promising for methyl-substituted heteroarenes with various alcohols (up to 96%).…”

Manganese‐Catalysed Dehydrogenative Coupling – An Overview

“…Kempe and co‐workers reported a manganese‐pincer catalysed α‐olefination of nitrogen‐containing heteroarenes using primary alcohols (Scheme ) . Among the various catalytic complexes screened the manganese‐PN 5 P pincer 113 was found to be an active catalyst while the corresponding iron and cobalt complexes were inactive.…”

“… Plausible catalytic cycle and reaction mechanism for the Mn‐catalysed alkene synthesis of methylheterocycles by Kempe et al. (reproduced with permission from Ref …”