100994-03-4Relevant academic research and scientific papers
Bimetallic Catalysis: Asymmetric Transfer Hydrogenation of Sterically Hindered Ketones Catalyzed by Ruthenium and Potassium
Slagbrand, Tove,Kivij?rvi, Tove,Adolfsson, Hans
, p. 3445 - 3449 (2015)
An efficient protocol for the asymmetric reduction of sterically hindered ketones under transfer-hydrogenation conditions was developed. The corresponding chiral alcohols were obtained in good to excellent yields with enantiomeric excess values up to 99 %. The role of the cation associated with the base present in the reduction reaction was investigated. In contrast to previous studies on this catalyst system, potassium ions rather than lithium ions significantly enhanced the reaction outcome.
Highly efficient NHC-iridium-catalyzed β-methylation of alcohols with methanol at low catalyst loadings
Lu, Zeye,Zheng, Qingshu,Zeng, Guangkuo,Kuang, Yunyan,Clark, James H.,Tu, Tao
, p. 1361 - 1366 (2021/06/30)
The methylation of alcohols is of great importance since a broad number of bioactive and pharmaceutical alcohols contain methyl groups. Here, a highly efficient β-methylation of primary and secondary alcohols with methanol has been achieved by using bis-N-heterocyclic carbene iridium (bis-NHC-Ir) complexes. Broad substrate scope and up to quantitative yields were achieved at low catalyst loadings with only hydrogen and water as by-products. The protocol was readily extended to the β-alkylation of alcohols with several primary alcohols. Control experiments, along with DFT calculations and crystallographic studies, revealed that the ligand effect is critical to their excellent catalytic performance, shedding light on more challenging Guerbet reactions with simple alcohols. [Figure not available: see fulltext.].
Manganese(I)-Catalyzed β-Methylation of Alcohols Using Methanol as C1 Source
Kaithal, Akash,van Bonn, Pit,H?lscher, Markus,Leitner, Walter
supporting information, p. 215 - 220 (2019/12/03)
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)2Br[HN(C2H4PiPr2)2]] 1 ([HN(C2H4PiPr2)2]=MACHO-iPr). 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.
Electrophile-Directed Diastereoselective Oxonitrile Alkylations
Chepyshev, Sergiy V.,Pitta, Bhaskar Reddy,Vangala, Saidi Reddy,Lujan-Montelongo, J. Armando,Steward, Omar W.,Fleming, Fraser F.
supporting information, p. 2850 - 2853 (2018/02/09)
Diastereoselective alkylation of prochiral oxonitrile dianions with secondary alkyl halides efficiently installs two contiguous stereogenic centers. The confluence of nucleophilic trajectory and the electrophile chirality causes distinct steric differences that allow efficient discrimination for one of the six possible conformers. Numerous oxonitrile-derived dianions efficiently displace secondary alkyl halides propagating the electrophile chirality to efficiently install two contiguous tertiary centers. The prevalence of chiral, secondary electrophiles makes the interdigitated alkylation of chiral electrophiles a particularly attractive route because the resulting oxonitriles are readily transformed into bioactive heterocycles.
Steric Effects in the Synthesis of 1,7-Dialkylindans
Budhram, Ronald S.,Palaniswamy, Ventakapuran A.,Eisenbraun, Edmund J.
, p. 1402 - 1406 (2007/10/02)
Synthesis routes to 1-alkyl(CH3,C2H5,i-C3H7)-6-methylindans and 1-alkyl(CH3,C2H5,i-C3H7)-7-methylindans are described.Members of the latter series, especially 1-isopropyl-7-methylindan, are sterically hindered through a peri interaction.This effect manifests itself throughout the study and necessitated use of alternative synthesis routes.Yields in the Grignard, Peterson olefination, Reformatsky, and Wittig reactions as well as catalytic hydrogenation and Li/NH3 reduction of α,β-unsaturated acids were compared.
