Mechanistic study on the ruthenium-catalyzed direct amination of alcohols

Dennis Pingen; Martin Lutz; Dieter Vogt

doi:10.1021/om4011998

Mechanistic study on the ruthenium-catalyzed direct amination of alcohols

Dennis Pingen, Martin Lutz, Dieter Vogt^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › Academic › peer-review

Abstract

The Ru-catalyzed direct amination of alcohols with ammonia was investigated for the RuHCl(CO)(PPh₃)₃/Xantphos system in order to gain mechanistic insight. For several Ru(II) precursor complexes the influence of different additives on catalytic performance was investigated. NMR studies revealed that the reaction of RuHCl(CO)(PPh₃)₃/Xantphos with the alcohol in the presence of a strong base initially formed an inactive dihydrido Ru species. However, by addition of a ketone, the dihydride was (re)activated, where the corresponding imine is the actual activator, formed by immediate condensation of the ketone with ammonia. In the absence of a base, added ketone significantly enhanced catalyst activity. Catalytically inactive RuCl₂(PPh₃)₃ could be activated by base, demonstrating that also complexes without the CO ligand give active catalysts. On the basis of these observations a mechanism was proposed, closely related to known transfer hydrogenation mechanisms.

Original language	English
Pages (from-to)	1623-1629
Number of pages	7
Journal	Organometallics
Volume	33
Issue number	7
DOIs	https://doi.org/10.1021/om4011998
Publication status	Published - 14 Apr 2014

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title = "Mechanistic study on the ruthenium-catalyzed direct amination of alcohols",

abstract = "The Ru-catalyzed direct amination of alcohols with ammonia was investigated for the RuHCl(CO)(PPh3)3/Xantphos system in order to gain mechanistic insight. For several Ru(II) precursor complexes the influence of different additives on catalytic performance was investigated. NMR studies revealed that the reaction of RuHCl(CO)(PPh3)3/Xantphos with the alcohol in the presence of a strong base initially formed an inactive dihydrido Ru species. However, by addition of a ketone, the dihydride was (re)activated, where the corresponding imine is the actual activator, formed by immediate condensation of the ketone with ammonia. In the absence of a base, added ketone significantly enhanced catalyst activity. Catalytically inactive RuCl2(PPh3)3 could be activated by base, demonstrating that also complexes without the CO ligand give active catalysts. On the basis of these observations a mechanism was proposed, closely related to known transfer hydrogenation mechanisms.",

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AU - Lutz, Martin

AU - Vogt, Dieter

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N2 - The Ru-catalyzed direct amination of alcohols with ammonia was investigated for the RuHCl(CO)(PPh3)3/Xantphos system in order to gain mechanistic insight. For several Ru(II) precursor complexes the influence of different additives on catalytic performance was investigated. NMR studies revealed that the reaction of RuHCl(CO)(PPh3)3/Xantphos with the alcohol in the presence of a strong base initially formed an inactive dihydrido Ru species. However, by addition of a ketone, the dihydride was (re)activated, where the corresponding imine is the actual activator, formed by immediate condensation of the ketone with ammonia. In the absence of a base, added ketone significantly enhanced catalyst activity. Catalytically inactive RuCl2(PPh3)3 could be activated by base, demonstrating that also complexes without the CO ligand give active catalysts. On the basis of these observations a mechanism was proposed, closely related to known transfer hydrogenation mechanisms.

AB - The Ru-catalyzed direct amination of alcohols with ammonia was investigated for the RuHCl(CO)(PPh3)3/Xantphos system in order to gain mechanistic insight. For several Ru(II) precursor complexes the influence of different additives on catalytic performance was investigated. NMR studies revealed that the reaction of RuHCl(CO)(PPh3)3/Xantphos with the alcohol in the presence of a strong base initially formed an inactive dihydrido Ru species. However, by addition of a ketone, the dihydride was (re)activated, where the corresponding imine is the actual activator, formed by immediate condensation of the ketone with ammonia. In the absence of a base, added ketone significantly enhanced catalyst activity. Catalytically inactive RuCl2(PPh3)3 could be activated by base, demonstrating that also complexes without the CO ligand give active catalysts. On the basis of these observations a mechanism was proposed, closely related to known transfer hydrogenation mechanisms.

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Mechanistic study on the ruthenium-catalyzed direct amination of alcohols

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