TY - JOUR
T1 - Green-Solvent Selection for Acyl Buchwald-Hartwig Cross-Coupling of Amides (Transamidation)
AU - Lei, Peng
AU - Wang, Yibo
AU - Mu, Yali
AU - Wang, Yujia
AU - Ma, Zhiqing
AU - Feng, Juntao
AU - Liu, Xili
AU - Szostak, Michal
N1 - Funding Information:
This work was financially supported by the Natural Science Basic Research Program of Shaanxi (No. 2020JQ-238), the Young Talent Fund of University Association for Science and Technology in Shaanxi (No. 2019-02-02), the National Natural Science Foundation of China (No. 32001930), and the Innovation Capability Support Plan of Shaanxi Province (2020TD-035). Rutgers University (M.S.) and the NSF (CAREER CHE-1650766, M.S.) are gratefully acknowledged for support.
Publisher Copyright:
© 2021 American Chemical Society.
PY - 2021/11/8
Y1 - 2021/11/8
N2 - The selection of solvents is essential as a suitable reaction milieu in chemical processes of industrial and academic impact. We present an evaluation of a range of green solvents for acyl Buchwald-Hartwig cross-coupling of amides to provide the first green-solvent selection guide for this powerful C-N to C-N′ cross-coupling interconversion engaging typically inert amide bonds, resulting in a net transamidation process of historically challenging amide bonds. Of the solvents considered, methyl tert-butyl ether (MTBE) and 2-methyltetrahydrofuran (2-MeTHF) were identified as the preferred alternative solvents for the acyl-Buchwald-Hartwig cross-coupling using well-defined and robust Pd(II)-NHC (NHC = N-heterocyclic carbene) precatalysts. MTBE and, in particular, 2-MeTHF are superior solvents in this cross-coupling manifold and recommended in terms of safety, health, biodegradability, and environmental score. The results indicate the replacement of hazardous solvents with green organic solvents in the biorelevant C-N to C-N′ cross-coupling manifold of amides to further the burgeoning chemical repertoire of amide-bond activation methods.
AB - The selection of solvents is essential as a suitable reaction milieu in chemical processes of industrial and academic impact. We present an evaluation of a range of green solvents for acyl Buchwald-Hartwig cross-coupling of amides to provide the first green-solvent selection guide for this powerful C-N to C-N′ cross-coupling interconversion engaging typically inert amide bonds, resulting in a net transamidation process of historically challenging amide bonds. Of the solvents considered, methyl tert-butyl ether (MTBE) and 2-methyltetrahydrofuran (2-MeTHF) were identified as the preferred alternative solvents for the acyl-Buchwald-Hartwig cross-coupling using well-defined and robust Pd(II)-NHC (NHC = N-heterocyclic carbene) precatalysts. MTBE and, in particular, 2-MeTHF are superior solvents in this cross-coupling manifold and recommended in terms of safety, health, biodegradability, and environmental score. The results indicate the replacement of hazardous solvents with green organic solvents in the biorelevant C-N to C-N′ cross-coupling manifold of amides to further the burgeoning chemical repertoire of amide-bond activation methods.
KW - 2-MeTHF
KW - 2-methyltetrahydrofuran
KW - Buchwald-Hartwig amination
KW - N-C(O) activation
KW - activated amides
KW - green-solvent selection
KW - methyl tert-butyl ether
KW - twisted amides
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U2 - 10.1021/acssuschemeng.1c05307
DO - 10.1021/acssuschemeng.1c05307
M3 - Article
AN - SCOPUS:85118667951
SN - 2168-0485
VL - 9
SP - 14937
EP - 14945
JO - ACS Sustainable Chemistry and Engineering
JF - ACS Sustainable Chemistry and Engineering
IS - 44
ER -