Science China Chemistry4 scope and up to quantitative yields were achieved at low catalyst loadings with only 5 hydrogen and water as by-products. The protocol was readily extended to the 6 β-alkylation of alcohols with several primary alcohols. Control experiments, along 7 with DFT calculations and crystallographic studies revealed that ligand effect is 8 critical for their excellent catalytic performance, shedding light on more challenging 9 Guerbet reactions with simple alcohols.
A practical, efficient, and mild hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) under 1 atm H2 was realized by single-sited 3D porous self-supported N-heterocyclic carbene iridium catalyts. Quantitative yields...
The
direct conversion of alcohols into long-chain alkanes is an
attractive but extremely challenging approach for biomass upgrading.
Here, we describe the highly selective deoxygenative coupling of aryl
ethanols with primary alcohols to produce alkanes, using a bis-N-heterocyclic
carbene iridium (bis-NHC-Ir) complex as the catalyst. Up to quantitative
yields and selectivity with a broad substrate scope are attained in
both homo- and cross-coupling reactions. Mechanistic studies reveal
that the further synergistic hydrogenation of the alkene intermediates
by the formate generated in situ in the presence of bis-NHC-Ir is
crucial for alkane production.
The Suzuki-Miyaura coupling of various (hetero) aryl chlorides with aryl boronic acids was accomplished by N-heterocyclic carbene-palladacycles (NHCÀ Pd cycle ) in the aqueous phase. Intriguingly, the NHCÀ Pd cycle with a constrained aliphatic linker between the NHC ligand and the palladacycle moieties exhibited higher catalytic efficiency than the one without constrained linker under the identical reaction conditions, due to the fixed spatial structure around the metal catalytic center. The present outcome may offer a new strategy for the catalyst design.Carbon-carbon (CÀ C) coupling reactions play a vital role in organic synthesis, pharmaceuticals, material science, and fine chemical industry. [1] Owing to the availability and safety of organoboron compounds and mild reaction conditions, the Suzuki-Miyaura coupling is regarded as one of the most widely appreciated methods for CÀ C coupling, especially for aryl-aryl bond construction. [2] In the past decades, N-heterocyclic carbene (NHC) ligands were considered as one of the viable candidates to realize Suzuki-Miyaura coupling due to their strong σ-donating and weak π-accepting ability, [3] which could remarkably facilitate the oxidation addition between the transition metals and aryl halides. [3b,4] On the other hand, the palladacycles (Pd cycle ) constituted privileged catalysts for the CÀ C and C-heteroatom formation reactions. [5] Combined both advantages, we and other groups have designed a series of NHCÀ Pd cycle complexes, revealing high activity in Suzuki-Miyaura reactions, decarboxylation reactions and Buchwald-Hartwig aminations. [6] Notwithstanding these advances, it is still difficult to achieve satisfactory performance using NHCÀ Pd cycle derived from imidazolium salts, especially with inert (hetero)aryl chlorides (Scheme 1a). [7] Recently, by using π-extended sterically bulky acenaphthoimidazolyidene, we successfully developed an NHCÀ Pd cycle 2, which did exhibit high catalytic activity and excellent substrate scopes toward the CÀ N and CÀ C coupling reactions with (hetero)aryl chlorides in toluene (Scheme 1b). [8] Despite these advances, it is still urgent to design efficient catalysts for Suzuki-Miyaura coupling reactions, especially, under sustainable reaction conditions like aqueous solvents, low reaction temperatures and low catalyst loadings from readily available imidazolium salts. [9] Herein, we synthesize a robust NHCÀ Pd cycle complex 3 a with constrained aliphatic linker between the [a] B.
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