Remarkable Effect of Subtle Structural Change of Chiral Pseudo-18-Crown-6 on Enantiomer-Selectivity in Complexation with Chiral Amino Alcohols
摘要:
Chiral receptors [(S,S)-1] and [(S,S,S,S)-2] having 1,2-dialkoxy-1-(3,5-dimethylphenyl)ethane and 1,2-dialkoxy-1-(3,5-dimethyl phenyl)cyclohexane as chiral building blocks, respectively, were prepared. Thermodynamic parameters of complexations of these and structurally related receptors [(S,S)-3] and [(S,S,S,S)-4] with 2-amino-1-propanol (5), 2-amino-2-phenylethanol (6), and 3-methylbutan-1-ol (7) in chloroform were determined. It was found that the host-guest systems that have same enantiomer-selectivity at 25 degrees C showed opposite selectivity in the enthalpy term. For example, complexations of both (SS)-1 and (SS)-3 with 5 are R-selective at 25 degrees C (Delta Delta G = 2.2 and 3.8 kJ mol(-1), respectively), whereas In terms of the enthalpy of complexation the former is S-selective (Delta Delta H = 22 kJ mol(-1)) but the latter is R-selective (Delta Delta H = 10 kJ mol(-1)).
Copper/Selectfluor-System-Catalyzed Dehydration-Oxidation of Tertiary Cycloalcohols: Access to β-Substituted Cyclohex-2-enones, 4-Arylcoumarins, and Biaryls
作者:Shaobo Ren、Jian Zhang、Jiahui Zhang、Heng Wang、Wei Zhang、Yunkui Liu、Miaochang Liu
DOI:10.1002/ejoc.201500610
日期:2015.8
A route to β-substitutedcyclohex-2-enones, 4-arylcoumarins, and biaryls has been developed. This approach involves a one-pot Cu0/Selectfluor-catalyzed dehydration–oxidation of tertiary cycloalcohols. Thus, by using 2 equiv. of Selectfluor at 25 °C, the dehydration–oxidation of tertiary cyclohexanols and oxabenzocyclohexanols gave β-substitutedcyclohex-2-enones and 4-arylcoumarins, respectively; whereas
Photoinduced Ligand-to-Metal Charge Transfer (LMCT) of Fe Alkoxide Enabled C–C Bond Cleavage and Amination of Unstrained Cyclic Alcohols
作者:Ting Xue、Zongnan Zhang、Rong Zeng
DOI:10.1021/acs.orglett.1c04365
日期:2022.1.28
an alkoxy radical process for the C–C bond cleavage and functionalization of unstrained tertiary and secondary cyclic alcohols. In the absence of a chlorine atom, the readily available iron catalysts [Fe(OBu-t)3 or Fe(acac)3/t-BuONa] facilitate alkoxy radical formation via the direct ligand-to-metal charge transfer of Fe alkoxide and further enable the ring opening and amination of cyclic alcohols.
我们报告了一种用于 C-C 键断裂和无应变叔和仲环醇官能化的烷氧基自由基过程。在没有氯原子的情况下,容易获得的铁催化剂 [Fe(OBu- t ) 3或 Fe(acac) 3 / t -BuONa] 通过烷氧基铁的直接配体到金属的电荷转移促进烷氧基自由基的形成,进一步使环状醇的开环和胺化成为可能。在温和的氧化还原中性体系下,可以以高产率获得范围广泛的远程氨基羰基化合物。光驱动的电子转移、烷氧基自由基的形成以及随后通过 β 断裂的 C-C 键断裂是转化的关键。
Ring-opening iodination and bromination of unstrained cycloalkanols through β-scission of alkoxy radicals
作者:Jiang-Ling Shi、Yuankai Wang、Zixuan Wang、Bowen Dou、Jianbo Wang
DOI:10.1039/d0cc01720e
日期:——
Ring-opening iodination or bromination of unstrained cycloalkanols with NaI or NaBr and PhI(OAc)2 under visible light irradiation is developed. In this protocol the concentration of I2 is modulated through the generation of triiodide (I3-), thus significantly avoiding undesired side reactions. The reaction is under mild conditions and has a wide substrate scope, thus providing a practically useful