Intramolecular anodic olefin coupling reactions: the use of bis enol ether substrates
摘要:
In an effort to develop electrochemical methods for directly initiating oxidative cyclization reactions, the anodic oxidation of bis enol ether substrates has been examined. The reactions were found to lead to the formation of five-, six-, and seven-membered-ring 1,4-dicarbonyl equivalents. The reactions were not found to be useful for generating larger ring sizes. Both alkyl and silyl enol ether substrates were found to be compatible with the conditions required for carbon-carbon bond formation. Cyclic voltammetry studies indicated that the cyclizations were fast and that the reactions happened at or near the electrode surface. Finally, the cyclization reactions were shown to be compatible with the formation of quaternary carbons, even when carbon-carbon bond formation involved the generation of two vicinal quaternary carbons.
Site-Selective Cu-Catalyzed Alkylation of α-Amino Acids and Peptides toward the Assembly of Quaternary Centers
作者:Marcos San Segundo、Arkaitz Correa
DOI:10.1002/cssc.201802216
日期:2018.11.23
The CuI‐catalyzed selective α‐alkylation of α‐amino acid and peptide derivatives with 2‐alkyl‐1,3‐dioxolanes is reported. This oxidative coupling is distinguished by its site‐specificity, high diastereoselectivity, and chirality preservation and exhibits absolute chemoselectivity for N‐aryl glycine motifs over other amino acid units. Collectively, the method allows for the assembly of challenging quaternary
An Efficient Synthesis of <i>p</i><i>eri</i>-Hydroxy Aromatic Compounds via a Strong-Base-Induced [4+2] Cycloaddition of Homophthalic Anhydrides with Enolizable Enones
作者:Kiyosei Iio、Namakkal G. Ramesh、Akiko Okajima、Kazuhiro Higuchi、Hiromichi Fujioka、Shuji Akai、Yasuyuki Kita
DOI:10.1021/jo990649q
日期:2000.1.1
An efficient synthesis of peri-hydroxy aromatic compounds has been accomplished via a strong-base-induced [4+2] cycloaddition of homophthalic anhydrides with alpha-sulfinyl-substituted derivatives of enolizable enones. The unsubstituted enones did not undergo an efficient [4+2] cycloaddition reaction with homophthalic anhydrides, presumably due to their enolization under the basic reaction conditions
Asymmetric Total Synthesis of Twin Bufogargarizins A and B
作者:Li-Ping Zhong、Rui Feng、Jing-Jing Wang、Chuang-Chuang Li
DOI:10.1021/jacs.2c13494
日期:2023.2.1
The first and asymmetric total synthesis of bufogargarizins A and B, two unusual and highly oxygenated twin steroids with rearranged A/B rings, was achieved. The synthetically challenging [7–5–6–5] tetracyclic ring system of bufogargarizin A was efficiently constructed by the first intramolecular Ru-catalyzed [5 + 2] cycloaddition reaction of a vinyl ether cyclopropane-yne. Notably, the interesting
bufogargarizins A 和 B 是两种不寻常且高度氧化的双类固醇,具有重排的 A/B 环,首次实现了不对称全合成。通过乙烯基醚环丙烷炔的第一个分子内 Ru 催化的 [5 + 2] 环加成反应,有效地构建了具有合成挑战性的 bufogargarizin A [7-5-6-5] 四环系统。值得注意的是,有趣的 [5-7-6-5] 蟾蜍加利津 B 四环骨架通过来自 [7-5-6-5] 四环框架的独特逆醛醇/跨环醛醇级联反应非对映选择性地重新组装。