Stereoselective Sequential Spirocyclopropanation/Cloke–Wilson Rearrangement Reactions for Synthesis of <i>trans</i>-β,γ-Disubstituted γ-Butyrolactones Using Alkylidene Meldrum’s Acid and Benzyl Halides
spirocyclopropanation/Cloke-Wilson rearrangement reactions have been developed to synthesize γ-butyrolactones using alkylidene Meldrum's acids and benzyl halides. The DBU-promoted spirocyclopropanation was carried out efficiently at room temperature to generate trans-isomeric spirocyclopropyl Meldrum's acid, and the following stereospecific thermal decarboxylative Cloke-Wilson rearrangement afforded trans-γ-butyrolactones
Arylidene Meldrum's acid is employed as a source of the arylgroup and oxidant for the synthesis of 2-aryl-1H–benzimidazoles by a condensation reaction with 1,2-phenylenediamine in refluxing ethanol with good to high yields. Arylidene Meldrum's acids were also used as a source of the arylgroup and oxidant for the synthesis of 2-aryl-1H-perimidines by a condensation reaction with 1,8-diaminonaphthalene
Synthesis of new Guanidium-Meldrum acid zwitterionic salts and dynamic NMR study of rotational energy barrier around C-NH bond of guanidine moiety
作者:Ali Aminkhani
DOI:10.13005/ojc/300439
日期:2014.12.31
Guanidium-Meldrum acid zwitterionic salts was developed through a three component reaction of 2, 2-dimethyl-1, 3-dioxane-4, 6-dione (Meldrum acid), aromatic aldehydes and N, N, N’, N’-Tetramethyl-guanidine in benzen at room temperature. These reaction conditions allow the preparation of stable zwitterionic salts in good yields. A dynamic NMR effect is observed as a result of restricted rotation around the C-NH bond
Catalyst-free transfer hydrogenation of activated alkenes exploiting isopropanol as the sole and traceless reductant
作者:Tamal Kanti Das、Agustin M. Rodriguez Treviño、Sanjay Pandiri、Sini Irvankoski、Juha H. Siitonen、Sara M. Rodriguez、Muhammed Yousufuddin、László Kürti
DOI:10.1039/d2gc04315g
日期:——
Both metal-catalyzed and organocatalytic transfer hydrogenation reactions are widely employed for the reduction of CO and CN bonds. However, selectivetransfer hydrogenation reactions of CC bonds remain challenging. Therefore, the chemoselective transfer hydrogenation of olefins under mild conditions and in the absence of metal catalysts, using readily available and inexpensive reducing agents (i.e
金属催化和有机催化转移加氢反应都广泛用于还原 C O 和 C N 键。然而,C C 键的选择性转移氢化反应仍然具有挑战性。因此,在温和条件下和在没有金属催化剂的情况下,使用容易获得且廉价的还原剂(即伯醇和仲醇)对烯烃进行化学选择性转移加氢,将标志着绿色转移加氢策略的发展取得了重大进展。本文描述的是活性烯烃的非常规无催化剂转移氢化反应,使用异丙醇作为环保还原剂和溶剂。该反应以中等至良好的收率方便地合成了多种取代的丙二酸半氧酯 (SMAHO)。机理研究指出了一种前所未有的氢键辅助转移氢化过程。
Alkylidene Meldrum′s Acid as Acceptor‐Donor‐Acceptor with Azomethine Ylide for Organocatalytic Asymmetric (3+2) Cycloaddition/Annulation: Synthesis of Chromeno[4,3‐<i>b</i>]pyrrolidine
作者:Yan‐Cheng Liou、Yi‐Ru Chen、Ching‐Wen Hsu、Xuan‐Rui Huang、Heng‐Wei Wang、Wenwei Lin
DOI:10.1002/adsc.202300609
日期:2023.11.7
A quinine-derived thiourea-catalyzed enantioselective double annulation strategy using alkylidene Meldrum′sacid as an acceptor-donor-acceptor with salicylaldehyde-derived azomethine ylide is reported. The methodology is realized via a (3+2) cycloaddition/transesterification/decarboxylation sequence, giving chromeno[4,3-b]pyrrolidines within 15–420 minutes at room temperature in 51–97% yields with