Shuhei Kusumoto

Direct and selective hydrogenolysis of arenols and aryl methyl ethers

For valorization of biomass, the conversion of lignin to deoxygenated bulk aromatic compounds is an emerging subject of interest. Because aromatic rings are susceptible to metal-catalysed hydrogenation, the selective hydrogenolysis of carbon-oxygen bonds still remains a great challenge. Herein we report direct and selective hydrogenolysis of sp(2) C-OH bonds in substituted phenols and naphthols catalysed by hydroxycyclopentadienyl iridium complexes. The corresponding arenes were obtained in up to 99% yields, indicating the possible production of arenes from lignin-derived bio-oils. Furthermore, the same catalysts were applied to the unprecedented selective hydrogenolysis of the sp(3) C-O bonds in aryl methyl ethers. Thus, the hydrodeoxygenation of vanillylacetone, a lignin model compound, afforded alkylbenzenes as the major products via triple deoxygenation.

Acceptorless Dehydrogenation of C–C Single Bonds Adjacent to Functional Groups by Metal–Ligand Cooperation

Unprecedented direct acceptorless dehydrogenation of C-C single bonds adjacent to functional groups to form α,β-unsaturated compounds has been accomplished by using a new class of group 9 metal complexes. Metal-ligand cooperation operated by the hydroxycyclopentadienyl ligand was proposed to play a major role in the catalytic transformation.

The Retro‐Hydroformylation Reaction

Hydroformylation, a reaction that adds carbon monoxide and dihydrogen across an unsaturated carbon-carbon multiple bond, has been widely employed in the chemical industry since its discovery in 1938. In contrast, the reverse reaction, retro-hydroformylation, has seldom been studied. The retro-hydroformylation reaction of an aldehyde into an alkene and synthesis gas (a mixture of carbon monoxide and dihydrogen) in the presence of a cyclopentadienyl iridium catalyst is now reported. Aliphatic aldehydes were converted into the corresponding alkenes in up to 91% yield with concomitant release of carbon monoxide and dihydrogen. Mechanistic control experiments indicated that the reaction proceeds by retro-hydroformylation and not by a sequential decarbonylation-dehydrogenation or dehydrogenation-decarbonylation process.

Addendum: The Retro-Hydroformylation Reaction.

DOI: 10.1002/anie.201503620 Following publication of this Communication, Dr. Boy Cornils (Hofheim, Germany) kindly informed the authors about the missing references for the retro-hydroformylation reaction. In the late 1960s, Orlicek[1] and inventors from Ruhrchemie AG[2] reported that cracking of isobutyraldehyde into propylene, carbon monoxide, and hydrogen was possible. The work was also published in academic literature in 1972.[3] In this reference, the two authors reported about the cracking of isobutyraldehyde, an undesired sideproduct of the oxo-process, to recover propylene and syngas using rhodium on alumina as a catalyst. Dr. Cornils comments that in 1972, his group confirmed the data in a months-andmonths run on a pilot plant scale. He says “it worked but not economically enough for industrial scale application.” In addition, in 1968, Tsuji et al. reported the formation of nonene as a major product in their attempt for decarbonylation of decanal with a heterogeneous palladium catalyst.[4]

CCDC 1841926: Experimental Crystal Structure Determination

Related Article: Satoko Takaoka, Aya Eizawa, Shuhei Kusumoto, Kazunari Nakajima, Yoshiaki Nishibayashi, Kyoko Nozaki|2018|Organometallics|||doi:10.1021/acs.organomet.8b00377