The reductive formylation of amines using CO2 and hydrosilanes is an attractive method for incorporating CO2 into valuable organic compounds. However, previous systems required either high catalyst loadings or high temperatures to achieve high efficiency, and the substrate scope was mostly limited to simple amines. To address these problems, a series of alkyl bridged chelating bis(NHC) rhodium complexes (NHC=N-heterocyclic carbene) have been synthesized and applied to the reductive formylation of amines using CO2 and Ph2SiH2. A rhodium-based bis(tzNHC) complex (tz=1,2,3-triazol-5-ylidene) was identified to be highly effective at a low catalyst loading and ambient temperature, and a wide substrate scope, including amines with reducible functional groups, were compatible.
NHC-rhodium complexes (NHC = Nheterocyclic carbenes) have been widely useda se fficient catalysts for hydrosilylation reactions.H owever, the substrates were mostly limited to reactive carbonyl compounds( aldehydes andk etones)o r carbon-carbon multiple bonds.H ere,w ed escribe the applicationo fn ewly-developed chelating bis(tzNHC)-rhodium complexes (tz = 1,2,3-triazol-5-ylidene)f or several reductivet ransformations.W ith these catalysts,t he formal reductive methylation of amines using carbon dioxide,t he hydrosilylation of amides and carboxylic acids,a nd the reductivea lkylation of amines using carboxylic acids have been achieved under mild reaction conditions.
A copper-catalyzed multicomponent coupling reaction between in situ generated ortho-arynes, terminal alkynes, and carbon dioxide was developed to access isocoumarins in moderate to good yields. The key to this CO2-incorporating reaction was the use of a versatile N-heterocyclic carbene/copper complex that was able to catalyze multiple transformations within the three-component reaction.
A facile synthetic procedure for the preparation of α‐trifluoromethyl carboxylic acids and esters was achieved through multicomponent coupling reactions between gem‐difluoroalkenes, cesium fluoride, and carbon dioxide. The products were generated in moderate to excellent yields, and the synthetic utility of this method was demonstrated through the preparation of trifluoromethylated versions of popular nonsteroidal anti‐inflammatory drugs (NSAIDs).
The first organocatalysed, metal-free cross-nucleophile coupling of indoles with α-branched aldehydes forming acyclic stereoselective quaternary carbon centres is presented.
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