Nonenzymatic Dynamic Kinetic Resolution of <i>in situ</i>
Generated Hemithioacetals: Access to 1,3-Disubstituted Phthalans
作者:Utpal Nath、Deepan Chowdhury、Subhas Chandra Pan
DOI:10.1002/adsc.201701518
日期:2018.4.17
The first nonenzymatic DKR reaction of hemithioacetals is developed. Hemithioacetals were formed in situ via thioladdition and subsequently underwent an intramolecular oxa‐Michael reaction. The scope of the reaction was quite broad ranging from aliphatic to aromatic substituents and 1,3‐disubstituted‐1,3‐dihyroisobenzofuran products were obtained in good yields with moderate diastereoselectivities
Organocatalytic, Enantioselective, Intramolecular Oxa-Michael Reaction of Alkoxyboronate: A New Strategy for Enantioenriched 1-Substituted 1,3-Dihydroisobenzofurans
An unprecedented strategy for the synthesis of enantioenriched 1-substituted 1,3-dihydroisobenzofurans via an enantioselective oxa-Michael reaction of o-alkoxyboronate containing chalcone (II) has been accomplished employing cinchona alkaloid based squaramide bifunctional organocatalyst in the presence of proton source. The corresponding alkoxyboronate intermediates have been readily prepared in situ
在质子源存在下,使用基于金鸡纳生物碱的方酰胺双功能有机催化剂,通过含有查耳酮 ( II ) 的邻烷氧基硼酸酯的对映选择性 oxa-Michael 反应,实现了合成对映体富集的 1-取代 1,3-二氢异苯并呋喃的前所未有的策略。使用中性硼烷作为氢化物源和作为催化剂对应物的叔胺部分,可以容易地由邻甲酰基查尔酮原位制备相应的烷氧基硼酸酯中间体。
Asymmetric Transfer Hydrogenation of (Hetero)arylketones with Tethered Rh(III)–<i>N</i>-(<i>p</i>-Tolylsulfonyl)-1,2-diphenylethylene-1,2-diamine Complexes: Scope and Limitations
A series of new tethered Rh(III)/Cp* complexes containing the N-(p-tolylsulfonyl)-1,2-diphenylethylene-1,2-diamine ligand have been prepared, characterized, and evaluated in the asymmetric transfer hydrogenation (ATH) of a wide range of (hetero)aryl ketones. The reaction was performed under mild conditions with the formic acid/triethylamine (5:2) system as the hydrogen source and provided enantiomerically
An easy entry to uncommon 2-propargylbenzaldehydes was developed. 2-Propargylbenzaldehydes demonstrated to be suitable building blocks for the synthesis of 3-benzyl isoquinolines by microwave promoted domino imination/cycloisomerisation in the presence of ammonium acetate. A small library of 3-benzyl isoquinolines was obtained in good yields under mild reaction conditions. Two alternative plausible reaction mechanisms are proposed.
The ligand-free Co-catalyzed chemoselective reductive cyclization cascade of enone-tethered aldehydes with i-PrOH as the environmentally benign hydrogen surrogate is developed by this study. Mechanistic studies disclosed that such a protocol is initiated by an ortho-enone-assisted Co(I)-catalyzed reduction of the aldehyde functionality with i-PrOH. Meanwhile, the selectivity from the Michael–Aldol