Kaithal Akash, van Bonn Pit, Hölscher Markus, Leitner Walter
Institut für Technische und Makromolekulare Chemie, RWTH Aachen University, Worringer Weg 2, 52074, Aachen, Germany.
Max-Planck-Institut für chemische Energiekonversion, Stiftstraße 34-36, 45470, Mülheim a.d. Ruhr, Germany.
Angew Chem Int Ed Engl. 2020 Jan 2;59(1):215-220. doi: 10.1002/anie.201909035. Epub 2019 Nov 28.
Highly selective β-methylation of alcohols was achieved using an earth-abundant first row transition metal in the air stable molecular manganese complex [Mn(CO) Br[HN(C H P Pr ) ]] 1 ([HN(C H P Pr ) ]=MACHO- Pr). The reaction requires only low loadings of 1 (0.5 mol %), methanolate as base and MeOH as methylation reagent as well as solvent. Various alcohols were β-methylated with very good selectivity (>99 %) and excellent yield (up to 94 %). Biomass derived aliphatic alcohols and diols were also selectively methylated on the β-position, opening a pathway to "biohybrid" molecules constructed entirely from non-fossil carbon. Mechanistic studies indicate that the reaction proceeds through a borrowing hydrogen pathway involving metal-ligand cooperation at the Mn-pincer complex. This transformation provides a convenient, economical, and environmentally benign pathway for the selective C-C bond formation with potential applications for the preparation of advanced biofuels, fine chemicals, and biologically active molecules.
使用一种储量丰富的第一排过渡金属，在空气稳定的分子锰配合物[Mn(CO)Br[HN(C6H3PPr2)2]] 1（[HN(C6H3PPr2)2]=MACHO-Pr）中实现了醇的高选择性β-甲基化。该反应仅需低负载量的1（0.5 mol %）、甲醇盐作为碱以及MeOH作为甲基化试剂和溶剂。各种醇都能以非常好的选择性（>99 %）和优异的产率（高达94 %）进行β-甲基化。源自生物质的脂肪醇和二醇也能在β-位进行选择性甲基化，为完全由非化石碳构建的“生物杂化”分子开辟了一条途径。机理研究表明，该反应通过涉及锰钳形配合物中金属-配体协同作用的借氢途径进行。这种转化为选择性C-C键形成提供了一条方便、经济且环境友好的途径，在制备高级生物燃料、精细化学品和生物活性分子方面具有潜在应用。
