614-54-0Relevant academic research and scientific papers
Selective C-alkylation Between Alcohols Catalyzed by N-Heterocyclic Carbene Molybdenum
Liu, Jiahao,Li, Weikang,Li, Yinwu,Liu, Yan,Ke, Zhuofeng
supporting information, p. 3124 - 3128 (2021/09/20)
The first implementation of a molybdenum complex with an easily accessible bis-N-heterocyclic carbene ligand to catalyze β-alkylation of secondary alcohols via borrowing-hydrogen (BH) strategy using alcohols as alkylating agents is reported. Remarkably high activity, excellent selectivity, and broad substrate scope compatibility with advantages of catalyst usage low to 0.5 mol%, a catalytic amount of NaOH as the base, and H2O as the by-product are demonstrated in this green and step-economical protocol. Mechanistic studies indicate a plausible outer-sphere mechanism in which the alcohol dehydrogenation is the rate-determining step.
C(sp3)-H selective benzylic borylation by in situ reduced ultrasmall Ni species on CeO2
Yoshii, Daichi,Yatabe, Takafumi,Yabe, Tomohiro,Yamaguchi, Kazuya
, p. 2150 - 2155 (2021/02/20)
Herein, we report that highly dispersed Ni hydroxide species supported on CeO2 act as an efficient heterogeneous catalyst for the selective borylation of benzylic C(sp3)-H bonds of alkylarenes including secondary derivatives, using pinacolborane as the bo
Photochemical oxidation of benzylic primary and secondary alcohols utilizing air as the oxidant
Nikitas, Nikolaos F.,Tzaras, Dimitrios Ioannis,Triandafillidi, Ierasia,Kokotos, Christoforos G.
supporting information, p. 471 - 477 (2020/02/13)
A mild and green photochemical protocol for the oxidation of alcohols to aldehydes and ketones was developed. Utilizing thioxanthenone as the photocatalyst, molecular oxygen from air as the oxidant and cheap household lamps or sunlight as the light source, a variety of primary and secondary alcohols were converted into the corresponding aldehydes or ketones in low to excellent yields. The reaction mechanism was extensively studied.
Chromium-Catalyzed Linear-Selective Alkylation of Aldehydes with Alkenes
Hirao, Yuki,Kanai, Motomu,Katayama, Yuri,Mitsunuma, Harunobu
supporting information, (2020/11/18)
We developed a chromium-catalyzed, photochemical, and linear-selective alkylation of aldehydes with alkylzirconium species generated in situ from a wide range of alkenes and Schwartz's reagent. Photochemical homolysis of the C-Zr bond afforded alkyl radicals, which were then trapped by a chromium complex catalyst to generate the alkylchromium(III) species for polar addition to aldehydes. The reaction proceeded with high functional group tolerance at ambient temperature under visible-light irradiation.
Highly Focused Library-Based Engineering of Candida antarctica Lipase B with (S)-Selectivity Towards sec-Alcohols
Cen, Yixin,Li, Danyang,Xu, Jian,Wu, Qiongsi,Wu, Qi,Lin, Xianfu
supporting information, p. 126 - 134 (2018/12/05)
Candida antarctica lipase B (CALB) is one of the most extensively used biocatalysts in both academia and industry and exhibits remarkable (R)-enantioselectivity for various chiral sec-alcohols. Considering the significance of tailor-made stereoselectivity in organic synthesis, a discovery of enantiocomplementary lipase mutants with high (R)- and (S)-selectivity is valuable and highly desired. Herein, we report a highly efficient directed evolution strategy, using only 4 representative amino acids, namely, alanine (A), leucine (L), lysine (K), tryptophan (W) at each mutated site to create an extremely small library of CALB variants requiring notably less screening. The obtained best mutant with three mutations W104V/A281L/A282K displayed highly reversed (S)-selectivity towards a series of sec-alcohol with E values up to 115 (conv. 50%, ee 94%). Compared with the previously reported (S)-selective CALB variant, W104A, a single mutation provided less selectivity, while the synergistic effects of three mutations in the best variant endow better (S)-selectivity and a broader substrate scope than the W104A variant. Structural analysis and molecular dynamics simulation unveiled the source of reversed enantioselectivity. (Figure presented.).
Transfer hydrogenation of ketones catalyzed by nickel complexes bearing an NHC [CNN] pincer ligand
Wang, Zijing,Li, Xiaoyan,Xie, Shangqing,Zheng, Tingting,Sun, Hongjian
, (2019/04/26)
Four NHC [CNN] pincer nickel (II) complexes, [iPrCNN (CH2)4-Ni-Br] (5a), [nBuCNN (CH2)4-Ni-Br] (5b), [iPrCNN (Me)2-Ni-Br] (6a) and [nBuCNN (Me)2-Ni-Br] (6b), bearing unsymmetrical [C (carbene)N (amino)N (amine)] ligands were synthesized by the reactions of [CNN] pincer ligand precursors 4 with Ni (DME)Cl2 in the presence of Et3N. Complexes 5a and 5b are new and were completely characterized. The transfer hydrogenation of ketones catalyzed by the four pincer nickel complexes were explored. Complexes 5a and 6a have better catalytic activity than 5b and 6b. With a combination of NaOtBu/iPrOH/80?°C and 2% catalyst loading of 5a, 77–98% yields of aromatic alcohols could be obtained.
Direct transformation of aryl 2-pyridyl esters to secondary benzylic alcohols by nickel relay catalysis
Wu, Xianqing,Li, Xiaobin,Huang, Wenyi,Wang, Yun,Xu, Hui,Cai, Liangzhen,Qu, Jingping,Chen, Yifeng
, p. 2453 - 2458 (2019/03/29)
A direct transformation of aryl esters to secondary benzylic alcohols via tandem Ni-catalyzed cross-coupling reactions of aromatic 2-pyridyl esters with alkyl zinc reagents and carbonyl group reduction by Ni-H species is achieved. Preliminary mechanistic studies reveal that the Ni-H species is generated in situ via β-hydride elimination of the Negishi reagents. The reaction is catalyzed by bench-stable nickel salts under mild conditions with wide functional group tolerance.
Regioselective Vinylation of Remote Unactivated C(sp3)?H Bonds: Access to Complex Fluoroalkylated Alkenes
Wu, Shuo,Wu, Xinxin,Wang, Dongping,Zhu, Chen
supporting information, p. 1499 - 1503 (2019/01/04)
Regioselective incorporation of a particular functional group into aliphatic sites by direct activation of unreactive C?H bonds is of great synthetic value. Despite advances in radical-mediated functionalization of C(sp3)?H bonds by a hydrogen-atom transfer process, the site-selective vinylation of remote C(sp3)?H bonds still remains underexplored. Reported herein is a new protocol for the regioselective vinylation of unactivated C(sp3)?H bonds. The remote C(sp3)?H activation is promoted by a C-centered radical instead of the commonly used N and O radicals. The reaction possesses high product diversity and synthetic efficiency, furnishing a plethora of synthetically valuable E alkenes bearing tri-/di-/mono-fluoromethyl and perfluoroalkyl groups.
Regioselective Sulfonylvinylation of the Unactivated C(sp3)-H Bond via a C-Centered Radical-Mediated Hydrogen Atom Transfer (HAT) Process
Yang, Shan,Wu, Xinxin,Wu, Shuo,Zhu, Chen
supporting information, p. 4837 - 4841 (2019/06/24)
Given the similarity of multiple sp3 C-H bonds in electronic properties and bond dissociation energy (BDE), regioselective sp3 C-H bond functionalization remains a paramount challenge. Here, we report a C-centered radical-mediated approach for site-specific sulfonylvinylation of the C(sp3)-H bond via the hydrogen atom transfer (HAT) process. The reaction features mild conditions, broad substrate scope, and high regioselectivity and stereoselectivity, manifesting the nontrivial synthetic potential.
Improved Enantioselectivity of Subtilisin Carlsberg towards Secondary Alcohols by Protein Engineering
Dorau, Robin,G?rbe, Tamás,Svedendahl Humble, Maria
, p. 338 - 346 (2017/12/26)
Generally, the catalytic activity of subtilisin Carlsberg (SC) for transacylation reactions with secondary alcohols in organic solvent is low. Enzyme immobilization and protein engineering was performed to improve the enantioselectivity of SC towards secondary alcohols. Possible amino-acid residues for mutagenesis were found by combining available literature data with molecular modeling. SC variants were created by site-directed mutagenesis and were evaluated for a model transacylation reaction containing 1-phenylethanol in THF. Variants showing high E values (>100) were found. However, the conversions were still low. A second mutation was made, and both the E values and conversions were increased. Relative to that shown by the wild type, the most successful variant, G165L/M221F, showed increased conversion (up to 36 %), enantioselectivity (E values up to 400), substrate scope, and stability in THF.
