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International audienceReaction of [Fe2{μ-S(CH2)3S}(CO)6] (1) at room temperature with the N-heterocyclic carbenes IMe-(CH2)2-L (IMe = 1-methylimidazol-2-ylidene, L = NMe2, SMe) afforded the pentacarbonyl carbene derivatives [Fe2{μ-S(CH2)3S}(CO)5{IMe-(CH2)2-NMe2}] (2a) and [Fe2{μ-S(CH2)3S}(CO)5{IMe-(CH2)2-SMe}] (2b). Reaction of 1 with IMe-CH2-IMe at room temperature provided the dimer [{Fe2(μ-S(CH2)3S)(CO)5}2{μ-(IMe-CH2-IMe)}] (3) together with the chelated bis-NHC complex [Fe2{μ-S(CH2)3S}(CO)4{IMe-CH2-IMe}] (4a) as the major product. The analogous reaction of 1 with IMe-(CH2)2-IMe yielded the chelated bis-NHC complex [Fe2(μ-S(CH2)3S)(CO)4{IMe-(CH2)2-IMe}] (4b). Addition of HBF4 to compound 4a afforded the stable bridging hydride complexes [Fe2(μ-H){μ-S(CH2)3S}(CO)4{IMe-CH2-IMe}](BF4) (5a,b) with NHC ligands in a basal/basal and basal/apical mode of coordination in 5a,b, respectively. The molecular structures of 2a, 3, 4a,b, and 5a were confirmed by X-ray diffraction studies. Low-temperature NMR studies on the protonation of 4a showed spectroscopic evidence for the formation of a very unstable terminal hydride and a bridging hydride species with a NHC ligand having a non classical mode of coordination via a C-4(5) bond. Cyclic voltammetry revealed that 4a is a catalyst for proton reduction

We report the synthesis of biomass-derived functionalized aromatic chemicals from furfural, a building block nowadays available in large scale from low-cost biomass. The scientific strategy relies on a Diels-Alder/aromatization sequence. By controlling the rate of each step, it was possible to produce exclusively the meta aromatic isomer. In particular, through this route, we describe the synthesis of renewably sourced meta-xylylenediamine (MXD). Transposition of this work to other furfural-derived chemicals is also discussed and reveals that functionalized biomass-derived aromatics (benzaldehyde, benzylamine, etc.) can be potentially produced, according to this route.

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