The selective coupling of alcohols is a fascinating yet challenging approach for upgrading alcohols. Herein, we accomplished the controlled production of β-disubstituted ketones or upgraded secondary alcohols via the...The selective coupling of alcohols is a fascinating yet challenging approach for upgrading alcohols. Herein, we accomplished the controlled production of β-disubstituted ketones or upgraded secondary alcohols via the Ir-catalyzed cross-coupling of secondary alcohols in excellent yields with broad substrate scopes. This selective control was achieved by using an in-situ generated monoNHC-Ir or a tris-NHC-Ir complex as the catalysts, respectively. Mechanistic studies revealed that the delicate balance between dehydrogenation and hydrogenation abilities of these bifunctional catalysts is crucial for achieving different selectivity. The tris-NHC-Ir complex effectively facilitated dehydrogenation of alcohols and hydrogenation of intermediates, leading to the desired upgraded secondary alcohols. Conversely, the high dehydrogenation ability of the mono-NHC-Ir complex promoted the conversion of formed secondary alcohols back to ketones.展开更多
The methylation of alcohols is of great importance since a broad number of bioactive and pharmaceutical alcohols contain methyl groups.Here,a highly efficientβ-methylation of primary and secondary alcohols with metha...The methylation of alcohols is of great importance since a broad number of bioactive and pharmaceutical alcohols contain methyl groups.Here,a highly efficientβ-methylation of primary and secondary alcohols with methanol has been achieved by using bis-N-heterocyclic carbene iridium(bis-NHC-Ir)complexes.Broad substrate scope and up to quantitative yields were achieved at low catalyst loadings with only hydrogen and water as by-products.The protocol was readily extended to theβ-alkylation of alcohols with several primary alcohols.Control experiments,along with DFT calculations and crystallographic studies,revealed that the ligand effect is critical to their excellent catalytic performance,shedding light on more challenging Guerbet reactions with simple alcohols.展开更多
基金supported by the National Natural Science Foundation of China(22271060)the Department of Chemistry at Fudan University。
文摘The selective coupling of alcohols is a fascinating yet challenging approach for upgrading alcohols. Herein, we accomplished the controlled production of β-disubstituted ketones or upgraded secondary alcohols via the Ir-catalyzed cross-coupling of secondary alcohols in excellent yields with broad substrate scopes. This selective control was achieved by using an in-situ generated monoNHC-Ir or a tris-NHC-Ir complex as the catalysts, respectively. Mechanistic studies revealed that the delicate balance between dehydrogenation and hydrogenation abilities of these bifunctional catalysts is crucial for achieving different selectivity. The tris-NHC-Ir complex effectively facilitated dehydrogenation of alcohols and hydrogenation of intermediates, leading to the desired upgraded secondary alcohols. Conversely, the high dehydrogenation ability of the mono-NHC-Ir complex promoted the conversion of formed secondary alcohols back to ketones.
基金This work was supported by the National Key R&D Program of China(2016YFA0202902)the National Natural Science Foundation of China(21871059,21861132002)and the Department of Chemistry at Fudan University.
文摘The methylation of alcohols is of great importance since a broad number of bioactive and pharmaceutical alcohols contain methyl groups.Here,a highly efficientβ-methylation of primary and secondary alcohols with methanol has been achieved by using bis-N-heterocyclic carbene iridium(bis-NHC-Ir)complexes.Broad substrate scope and up to quantitative yields were achieved at low catalyst loadings with only hydrogen and water as by-products.The protocol was readily extended to theβ-alkylation of alcohols with several primary alcohols.Control experiments,along with DFT calculations and crystallographic studies,revealed that the ligand effect is critical to their excellent catalytic performance,shedding light on more challenging Guerbet reactions with simple alcohols.
