Catalytic Syntheses of N-Heterocyclic Ynones and Ynediones by In Situ Activation of Carboxylic Acids with Oxalyl Chloride
作者:Christina Boersch、Eugen Merkul、Thomas J. J. Müller
DOI:10.1002/anie.201103296
日期:2011.10.24
bottleneck: α‐Keto carboxylicacids and N‐heterocyclic carboxylicacids are activated in situ with oxalylchloride then catalytically alkynylated to give ynediones and N‐heterocyclic ynones efficiently in a one‐pot fashion. 5‐Acylpyrazoles and 2‐phenylaminopyrimidines, potentially interesting for pharmaceutical applications, are readily synthesized in concise one‐pot, three‐component syntheses.
A Novel Catalytic and Highly Enantioselective Approach for the Synthesis of Optically Active Carbohydrate Derivatives
作者:Hélène Audrain、Jacob Thorhauge、Rita G. Hazell、Karl Anker Jørgensen
DOI:10.1021/jo9918596
日期:2000.7.1
yield, high diastereoselectivity, and excellent enantioselectivity. The potential of the reaction is demonstrated by the synthesis of optically active carbohydrates such as spiro-carbohydrates, an ethyl beta-D-mannoside tetraacetate, and acetal-protected C-2-branched carbohydrates. On the basis of X-ray crystallographic data and the absolute configuration of the products, it is proposed that the alkene
allylboronic acids to β,γ‐unsaturatedα‐ketoesters has been realized by employing a chiral NiII/N,N′‐dioxide complex as the catalyst. This transformation proceeds by an allylboration/oxy‐Cope rearrangement sequence, providing a facile and rapid route to γ‐allyl‐α‐ketoesters with moderate to good yields (65–92 %) and excellent ee values (90–99 % ee). The isolation of 1,2‐allylboration products provided insight
通过使用手性Ni II / N,N'-二氧化物络合物作为催化剂,已实现了对β,γ-不饱和α-酮酸酯的烯丙基硼酸的高度对映体选择性形式共轭烯丙基加成。该转化过程通过烯丙基硼化/ oxy-Cope重排序列进行,提供了简便且快速的途径,以中等至良好的收率(65-92%)和出色的ee值(90-99%ee)转化为γ-烯丙基-α-酮酸酯)。1,2-烯丙基化产物的分离提供了对随后oxy-Cope重排反应机理的认识:底物诱导的手性转移和手性Lewis酸加速过程。在实验研究和DFT计算的基础上,提出了一种罕见的船状过渡态模型,作为氧-科普重排过程中高手性转移的起源。
Catalytic Enantioselective Inverse Electron Demand Hetero-Diels-Alder Reaction with Allylsilanes
The first diastereo‐ and enantioselectiveinverseelectrondemandhetero‐Diels–Alderreaction of β,γ‐unsaturated α‐ketoesters with allylsilanes is described. Chiralcopper(II) catalysts successfully activate the β,γ‐unsaturated α‐ketoesters and promote the reaction with allylsilanes with excellent enantioselectivities. This process represents a new entry to chiral oxanes.
F<sup>–</sup>-Free Deoxyhydrotrifluoromethylation of α-Keto Esters with Ph<sub>3</sub>P<sup>+</sup>CF<sub>2</sub>CO<sub>2</sub><sup>–</sup>: Synthesis of α–CF<sub>3</sub>-Substituted Esters
作者:Ying Zheng、Yimin Jia、Yuan Yuan、Zhong-Xing Jiang、Zhigang Yang
DOI:10.1021/acs.joc.0c01518
日期:2020.8.21
direct deoxyhydrotrifluoromethylation of α-keto esters with a difluoromethylating reagent has been achieved, in which the employment of water can promote the dissociation of the CF2 group to form a CF3 moiety, which provides the successful transformation. The current protocol demonstrates one of the most practical approaches to generate α-trifluoromethyl esters with a broad substrate scope and high functional