Transamidation of Amides and Amidation of Esters by Selective N-C(O)/O-C(O) Cleavage Mediated by Air- and Moisture-Stable Half-Sandwich Nickel(II)-NHC Complexes

• Published in: Molecules (Basel, Switzerland) Switzerland), 2021-01, Vol.26 (1), p.188
• Main Authors: Buchspies, Jonathan, Rahman, Md Mahbubur, Szostak, Michal
• Format: Article
• Language: English
• Subjects: Air; Amides; Amides - chemistry; Aniline; Aniline Compounds - chemistry; Buchwald–Hartwig; Carbenes; Catalysis; Chemistry Techniques, Synthetic; Cleavage; Conversion; Esters; Esters - chemistry; Kinetics; Methane - analogs & derivatives; Methane - chemistry; Moisture; N-heterocyclic carbenes; NHCs; Nickel; Nickel - chemistry; Nitrogen - chemistry; Organometallic Compounds - chemistry; Phenolic compounds; Phenols; transamidation; Transition metals; twisted amides
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/MOLECULES26010188

The formation of amide bonds represents one of the most fundamental processes in organic synthesis. Transition-metal-catalyzed activation of acyclic twisted amides has emerged as an increasingly powerful platform in synthesis. Herein, we report the transamidation of -activated twisted amides by selective N-C(O) cleavage mediated by air- and moisture-stable half-sandwich Ni(II)-NHC (NHC = N-heterocyclic carbenes) complexes. We demonstrate that the readily available cyclopentadienyl complex, [CpNi(IPr)Cl] (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), promotes highly selective transamidation of the N-C(O) bond in twisted N-Boc amides with non-nucleophilic anilines. The reaction provides access to secondary anilides via the non-conventional amide bond-forming pathway. Furthermore, the amidation of activated phenolic and unactivated methyl esters mediated by [CpNi(IPr)Cl] is reported. This study sets the stage for the broad utilization of well-defined, air- and moisture-stable Ni(II)-NHC complexes in catalytic amide bond-forming protocols by unconventional C(acyl)-N and C(acyl)-O bond cleavage reactions.