Palladium-N-Heterocyclic Carbene (NHC)-Catalyzed Asymmetric Synthesis of Indolines through Regiodivergent C(sp<sup>3</sup>)H Activation: Scope and DFT Study
作者:Dmitry Katayev、Evgeny Larionov、Masafumi Nakanishi、Céline Besnard、E. Peter Kündig
DOI:10.1002/chem.201403985
日期:2014.11.10
Two bulky, chiral, monodentate N‐heterocyclic carbene ligands were applied to palladium‐catalyzed asymmetricCH arylation to incorporate C(sp3)H bond activation. Racemic mixtures of the carbamate starting materials underwent regiodivergent reactions to afford different trans‐2,3‐substituted indolines. Although this CArCalkyl coupling requires high temperatures (140–160 °C), chiral induction is high
Thiourea: A Novel Cleaving Agent for 1,3-Dioxolanes
作者:Swapan Majumdar、Anup Bhattacharjya
DOI:10.1021/jo981115c
日期:1999.7.1
Deprotection of Acetals and Silyl Ethers Using a Polymer-Supported π-Acid Catalyst: Chemoselectivity and Polymer Effect
作者:Nobuyuki Tanaka、Yukio Masaki
DOI:10.1055/s-1999-3000
日期:1999.12
A polymeric dicyanoketene acetal (DCKA), prepared from a styrene monomer bearing dicyanoketene acetal functionality, was found to be an effective and recyclable catalyst in the chemoselective deprotection of acetals and silyl ethers. A remarkable acceleration accountable for the polymer effect was observed.
compound is not a resorcylic acid lactone but a resorcylic acid substituted with a butenolide, and thus is the first member of a new class of alternaria toxins. For the total synthesis, a short and efficient access to halogenated butenolides bearing acetal-protected side-chains was carried out. Suzuki coupling of these butenolides with a highly functionalized boronate gave rise to a precursor of the natural
链格孢霉菌毒素链状核菌酸 III 的结构通过真实样品的 NMR 光谱分析得到阐明,并通过全合成得到证实。该化合物不是间苯二酸内酯,而是用丁烯内酯取代的间苯二酸,因此是新一类链格孢毒素的第一个成员。对于全合成,进行了对带有缩醛保护侧链的卤化丁烯内酯的简短而有效的访问。这些丁烯内酯与高度官能化的硼酸酯的 Suzuki 偶联以高产率产生了天然产物的前体。通过脱保护和随后的氧化完成侧链。在优化脱保护方案期间发现了导致三环丁烯内酯的意外级联反应。裂解缩醛保护基团得到阿尔丁酸III。此外,还描述了对具有特征性螺内酯结构的化合物 altenuic acid II 的合成研究。计划通过使用芳香羧酸酯基团与丁烯内酯部分的分子内迈克尔型加成来构建螺环内酯,但这种方法没有成功。在测试这一概念的可行性时,发现了一种新的温和方案,用于在路易斯酸存在下进行众所周知的 Pinner 反应。但这种方法并不成功。在测试这一