The first N-Heterocyclic Carbene (NHC) mediated activation of stable carboxylate esters to generate enolate intermediates is disclosed. The catalytically generated arylacetic ester enolates undergo enantioselective reactions with α,β-unsaturated imines.

Copper and zirconium oxide clusters were highly dispersed on mesocellular siliceous foam (MCF), a mesoporous silica support with ultra large, interconnected nanopores. These catalysts (denoted as Cu/MCF and Zr/MCF) were separately loaded into two fixed bed reactors as catalysts for the conversion of ethanol (EtOH) to 1,3-butadiene (BD). Under optimal conditions, high BD selectivity (up to 73%) and ethanol conversion (up to 96%) were achieved at weight hourly space velocities of 1.5 and 3.7 h −1 . This translates to an unprecedented productivity of 1.4 g BD /g catalyst h −1 (208 g BD /l catalyst h −1 ). The high catalytic performance is attributed to the highly selective and active catalysts. The EtOH dehydrogenation activity of Cu/MCF could be accurately controlled in the first reactor, which delivers a fixed ratio of the acetaldehyde/EtOH mixture to Zr/MCF in the second reactor. The optimal ratio minimizes EtOH dehydration to ethylene by Zr/MCF, while maximizing the selectivity to BD. MCF was found to be superior over commercial porous silica in terms of EtOH conversion, BD selectivity, and tolerance to coking. High BD selectivity was maintained with a slight decrease in EtOH conversion over 42 h, which was readily restored upon regeneration by thermal treatment in air.

An unprecedented N-heterocyclic carbene catalytic reductive β,β-carbon coupling of α,β-nitroalkenes, by using an organic substrate to mimic the one-electron oxidation role of the pyruvate ferredoxin oxidoreductase (PFOR) in living systems, has been developed. The reaction goes through a radical anion intermediate generated under a catalytic redox process. For the first time, the presence of radical anion intermediate in NHC organocatalysis is observed and clearly verified.

Arylacetic ester enolates, generated in situ, react with α,β‐unsaturated imines to afford highly substituted N‐tosyl dihydropyridinones.

Intermediates. -The coupling of nitroalkenes in the presence of a NHC-catalyst and aldehydes as reducing agents provides dl-diastereomers (II) and (VII) as major products. The formation of an intermediate radical anion is clearly confirmed. -(DU, Y.; WANG, Y.; LI, X.; SHAO, Y.; LI, G.; WEBSTER, R. D.; CHI*, Y. R.; Org. Lett. 16 (2014) 21, 5678-5681, http://dx.