The α-alkylation of ketones using an earth-abundant and nonprecious NiBr2/L1 system is reported. This nickel-catalyzed reaction could be performed in gram scale and successfully applied in the synthesis of donepezil (Alzheimer’s drug) and functionalization of steroid hormones and fatty acid derivatives. Synthesis of N-heterocycles, methylation of ketones, and one-pot double alkylation to bis-hetero
Herein an operationally simple alkylation of methylene ketones with primary alcohols is reported. Use of an inexpensive and earth abundant Mn/1,10-phenanthroline system enables direct access to a series of functionalised branchedketones including one-pot sequential double alkylation and Alzheimer's drug donepezil. Preliminary mechanistic investigation, determination of the rate and order of reactions
Cobalt(II)-Catalyzed Stereoselective Olefin Isomerization: Facile Access to Acyclic Trisubstituted Alkenes
作者:Sheng Zhang、Deepika Bedi、Lu Cheng、Daniel K. Unruh、Guigen Li、Michael Findlater
DOI:10.1021/jacs.0c02101
日期:2020.5.13
Stereoselective synthesis of trisubstitutedalkenes is a long-standing challenge in organic chemistry, due to the small energy differences between E and Z isomers of trisubstitutedalkenes (compared with 1,2-disubstituted alkenes). Transition metal-catalyzed isomerization of 1,1-disubstituted alkene can serve as an alternative approach to trisubsti-tuted alkenes, but it remains underdeveloped owing
三取代烯烃的立体选择性合成是有机化学中长期存在的挑战,因为三取代烯烃的 E 和 Z 异构体之间的能量差异很小(与 1,2-二取代烯烃相比)。1,1-二取代烯烃的过渡金属催化异构化可以作为三取代烯烃的替代方法,但由于与反应效率和立体选择性有关的问题,它仍然不发达。在这里,我们展示了一种新型钴催化剂可以克服这些挑战,为获得广泛的三取代烯烃提供有效和立体选择性的途径。该协议与单烯和二烯兼容,并表现出良好的官能团耐受性和可扩展性。而且,它已被证明是构建有机发光体和氘代三取代烯烃的有用工具。对该机制的初步研究表明,该反应涉及钴氢化物途径。该反应的高立体选择性归因于 π-π 堆积效应和底物和催化剂之间的空间位阻。
作者:Marcileia Zanatta、Francisco P. dos Santos、Cristina Biehl、Graciane Marin、Gunter Ebeling、Paulo A. Netz、Jairton Dupont
DOI:10.1021/acs.joc.6b03029
日期:2017.3.3
for the H/Dexchange reaction of various substrates using CDCl3 as D source, without the addition of any extra bases or metal. High deuterium incorporation (up to 49%) in acidic C–H bonds of ketone and alkyne substrates (pKa from 18.7 to 28.8) was found at room temperature. The reaction proceeds through the fast and reversible deuteration of the 2-methyl H of the imidazolium cation followed by D transfer
与碱性阴离子(例如碳酸氢盐,脯氨酸盐和咪唑酸盐)缔合的简单1,2,3-三烷基咪唑鎓阳离子是使用CDCl 3作为D源进行各种底物H / D交换反应的活性催化剂,而无需添加任何多余的碱或金属。酮和炔烃底物的酸性C–H键中氘的高掺入量(最高49%)(p K a在室温下发现(从18.7到28.8)。反应通过咪唑鎓阳离子的2-甲基H的快速可逆氘化进行,然后D转移至底物。IL充当中性碱催化剂,其中在反应过程中保持接触离子对。碱性活性位点归因于阴离子中存在一个偏远的碱性位点,即碳酸氢根的OH,脯氨酸根的NH和咪唑基阴离子中的活化水。详细的动力学实验表明,由于涉及溶剂对离子液体进行氘化的快速可逆反应,因此该反应在底物上相对于离子液体为一级伪零级。
Brønsted Acid Catalyzed Friedel–Crafts‐Type Coupling and Dedinitrogenation Reactions of Vinyldiazo Compounds
作者:Haifeng Zheng、Kuiyong Dong、Daniel Wherritt、Hadi Arman、Michael P. Doyle
DOI:10.1002/anie.202004328
日期:2020.8.3
The direct Friedel–Crafts‐type coupling and dedinitrogenation reactions of vinyldiazo compounds with aromatic compounds using a metal‐free strategy are described. This Brønsted acid catalyzed method is efficient for the formation of α‐diazo β‐carbocations (vinyldiazonium ions), vinyl carbocations, and allylic or homoallylic carbocation species via vinyldiazo compounds. By choosing suitable nucleophilic