Abstract
The transition-metal-catalyzed direct synthesis of amides from alcohols and amines is herein demonstrated as a highly environmentally benign and atom-economic process. Among various catalyst systems, insitu generated N-heterocyclic carbene (NHC)-based ruthenium (Ru) halide catalyst systems have been proven to be active for this transformation. However, these existing catalyst systems usually require an additional ligand to achieve satisfactory results. In this work, through extensive screening of a diverse variety of NHC precursors, we discovered an active insitu catalyst system for efficient amide synthesis without any additional ligand. Notably, this catalyst system was found to be insensitive to the electronic effects of the substrates, and various electron-deficient substrates, which were not highly reactive with our previous catalyst systems, could be employed to afford the corresponding amides efficiently. Furthermore, mechanistic investigations were performed to provide a rationale for the high activity of the optimized catalyst system. NMR-scale reactions indicated that the rapid formation of a Ru hydride intermediate (signal at δ=-7.8ppm in the 1HNMR spectrum) after the addition of the alcohol substrate should be pivotal in establishing the high catalyst activity. Besides, HRMS analysis provided possible structures of the insitu generated catalyst system.
| Original language | English |
|---|---|
| Pages (from-to) | 440-448 |
| Number of pages | 9 |
| Journal | Chemistry - An Asian Journal |
| Volume | 13 |
| Issue number | 4 |
| DOIs | |
| Publication status | Published - 16 Feb 2018 |
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Keywords
- Amides
- Atom economy
- Carbenes
- Reaction mechanisms
- Ruthenium
ASJC Scopus subject areas
- Chemistry(all)
Cite this
Insitu Generated Ruthenium Catalyst Systems Bearing Diverse N-Heterocyclic Carbene Precursors for Atom-Economic Amide Synthesis from Alcohols and Amines. / Cheng, Hua; Xiong, Mao Qian; Cheng, Chuan Xiang; Wang, Hua Jing; Lu, Qiang; Liu, Hong Fu; Yao, Fu Bin; Verpoort, Francis; Chen, Cheng.
In: Chemistry - An Asian Journal, Vol. 13, No. 4, 16.02.2018, p. 440-448.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Insitu Generated Ruthenium Catalyst Systems Bearing Diverse N-Heterocyclic Carbene Precursors for Atom-Economic Amide Synthesis from Alcohols and Amines
AU - Cheng, Hua
AU - Xiong, Mao Qian
AU - Cheng, Chuan Xiang
AU - Wang, Hua Jing
AU - Lu, Qiang
AU - Liu, Hong Fu
AU - Yao, Fu Bin
AU - Verpoort, Francis
AU - Chen, Cheng
PY - 2018/2/16
Y1 - 2018/2/16
N2 - The transition-metal-catalyzed direct synthesis of amides from alcohols and amines is herein demonstrated as a highly environmentally benign and atom-economic process. Among various catalyst systems, insitu generated N-heterocyclic carbene (NHC)-based ruthenium (Ru) halide catalyst systems have been proven to be active for this transformation. However, these existing catalyst systems usually require an additional ligand to achieve satisfactory results. In this work, through extensive screening of a diverse variety of NHC precursors, we discovered an active insitu catalyst system for efficient amide synthesis without any additional ligand. Notably, this catalyst system was found to be insensitive to the electronic effects of the substrates, and various electron-deficient substrates, which were not highly reactive with our previous catalyst systems, could be employed to afford the corresponding amides efficiently. Furthermore, mechanistic investigations were performed to provide a rationale for the high activity of the optimized catalyst system. NMR-scale reactions indicated that the rapid formation of a Ru hydride intermediate (signal at δ=-7.8ppm in the 1HNMR spectrum) after the addition of the alcohol substrate should be pivotal in establishing the high catalyst activity. Besides, HRMS analysis provided possible structures of the insitu generated catalyst system.
AB - The transition-metal-catalyzed direct synthesis of amides from alcohols and amines is herein demonstrated as a highly environmentally benign and atom-economic process. Among various catalyst systems, insitu generated N-heterocyclic carbene (NHC)-based ruthenium (Ru) halide catalyst systems have been proven to be active for this transformation. However, these existing catalyst systems usually require an additional ligand to achieve satisfactory results. In this work, through extensive screening of a diverse variety of NHC precursors, we discovered an active insitu catalyst system for efficient amide synthesis without any additional ligand. Notably, this catalyst system was found to be insensitive to the electronic effects of the substrates, and various electron-deficient substrates, which were not highly reactive with our previous catalyst systems, could be employed to afford the corresponding amides efficiently. Furthermore, mechanistic investigations were performed to provide a rationale for the high activity of the optimized catalyst system. NMR-scale reactions indicated that the rapid formation of a Ru hydride intermediate (signal at δ=-7.8ppm in the 1HNMR spectrum) after the addition of the alcohol substrate should be pivotal in establishing the high catalyst activity. Besides, HRMS analysis provided possible structures of the insitu generated catalyst system.
KW - Amides
KW - Atom economy
KW - Carbenes
KW - Reaction mechanisms
KW - Ruthenium
UR - http://www.scopus.com/inward/record.url?scp=85041128904&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85041128904&partnerID=8YFLogxK
U2 - 10.1002/asia.201701734
DO - 10.1002/asia.201701734
M3 - Article
VL - 13
SP - 440
EP - 448
JO - Chemistry - An Asian Journal
JF - Chemistry - An Asian Journal
SN - 1861-4728
IS - 4
ER -