Direct Synthesis of Cyclopropanes from <i>gem</i>-Dialkyl Groups through Double C–H Activation
作者:Antonin Clemenceau、Pierre Thesmar、Maxime Gicquel、Alexandre Le Flohic、Olivier Baudoin
DOI:10.1021/jacs.0c05887
日期:2020.9.9
numerous bioactive molecules, and a number of methods are available for their synthesis. However, one of the simplest cyclopropanation reactions involving the intramolecular coupling of two C-H bonds in a single step has remained an elusive transformation. We demonstrate herein that this reaction is accessible using aryl bromide or triflate precursors and the 1,4-Pd shift mechanism. The use of pivalate
Directed lithiations: the effect of varying directing group orientation on competitive efficiencies for a series of tertiary amide, secondary amide, and alkoxide directed ortho lithiations
作者:Peter Beak、Shawn T. Kerrick、Donald J. Gallagher
DOI:10.1021/ja00076a022
日期:1993.11.1
Significant differences for competitive efficiencies in directed ortho lithiations for single functional groups in three series, the secondary benzamides 1-4, the tertiary benzamides 5-11, and the benzylic alcohols 12-17, are reported. For both amide series the efficiencies increase as the oxygen and ortho hydrogen in the substrate are more coplanar with the aromatic ring; however, for the alcohol
Does formal intramolecular transfer of an acidic deuterium to a site of halogen-lithium exchange show that lithium-halogen exchange is faster than loss of the acidic deuterium? Evidence in favor of an alternative mechanism
作者:Peter. Beak、Timothy J. Musick、Chin Wen. Chen
DOI:10.1021/ja00219a031
日期:1988.5
They suggest an alternative in which initial loss of the acidic deuterium is followed by halogen-lithium exchange to give a dilithiated intermediate. Deuterium transfer to the site of halogen-lithium exchange then occurs by reaction of the dilithiated species intermolecularly with unreacted N-deuteriated amide. The halogen-lithium exchange is faster than complete mixing of the reactants and can occur
Organoselenium-catalyzed enantioselective syn-dichlorination of unbiased alkenes
作者:Bradley B. Gilbert、Stanley T.-C. Eey、Pavel Ryabchuk、Olivia Garry、Scott E. Denmark
DOI:10.1016/j.tet.2019.05.054
日期:2019.8
the enantioselective suprafacial dichlorination of alkenes catalyzed by electrophilic organoselenium reagents has been developed to address these limitations. The evaluation of twenty-three diselenides as precatalysts for enantioselective dichlorination is described, with a maximum e.r. of 76:24 Additionally, mechanistic studies suggest an unexpected DynamicKineticAsymmetricTransformation (DyKAT)
烯烃的对映选择性二氯化是有机合成中持续存在的挑战,因为亲电子氯和亲核氯化物选择性和独立地反面递送至烯烃的局限性。开发用于分离烯烃的对映选择性二氯化的通用方法将允许获得多种多卤代天然产物。因此,已经开发了由亲电子有机硒试剂催化的烯烃的对映选择性表面二氯化来解决这些限制。描述了对 23 种二硒化物作为对映选择性二氯化反应预催化剂的评估,最大 er 为 76:24 此外,机理研究表明意外的动态动力学不对称转化 (DyKAT) 过程可能是有效的。
A Dramatic Switch of Enantioselectivity in Asymmetric Heck Reaction by Benzylic Substituents of Ligands
synthesized. The Pd-complexes of these ligands show high catalytic activity and enantioselectivity in catalyzing the asymmetricHeckreaction. A dramatic switch in enantioselectivity is realized usingligands with and without substituents at the benzylic position of the ligand. Ligands 1 with H as the substituents offer products in (R)-configuration while ligands 2 with the methyl as substituents result