Deprotection of Acetals and Silyl Ethers by DDQ. Is DDQ a Neutral Catalyst?
作者:Akira Oku、Motoharu Kinugasa、Tohru Kamada
DOI:10.1246/cl.1993.165
日期:1993.1
2,3-Dichloro-5,6-dicyano-p-benzoquinone (DDQ) in wet ethyl acetate at room temperature catalytically hydrolyzed acyclic acetals effectively and selectively among ethereal functional groups such as dioxoranes, 1,3-dioxanes, oxiranes, TMS- and TBDMS ethers. The mechanism is discussed on the basis of the function of DDQ as a Lewis acid in a wet solvent.
NEW APPLICATIONS OF SOLID SILICA CHLORIDE (─SiO<sub>2</sub>Cl): EFFICIENT OXIDATION OF CYCLIC THIOACETALS, TMS, TBDMS, AND THP ETHERS TO THEIR CARBONYL COMPOUNDS BY SOLID SILICA CHLORIDE/KMnO<sub>4</sub> SYSTEM
aromatic and aliphatic cyclic thioacetals (1,3-dithiolanes, 1,3-dithianes) and silyl and pyranyl ethers into their corresponding carbonylcompounds in dry CH3CN at room temperature in high yields. Over-oxidation of aldehydes to carboxylic acids has not been observed by this system. In the absence of silica chloride, KMnO4 in dry CH3CN is an ineffective reagent for these oxidations.
Single-Step Dual Functionalization: One-Pot Bromination-Cross-Dehydrogenative Esterification of Hydroxy Benzaldehydes with CCl3Br – A Comparison with Selectfluor
作者:Ranadeep Talukdar
DOI:10.1055/s-0037-1610717
日期:2019.9
Bromination of phenolic compounds without directly using molecular bromine possesses much importance. In this article an IrIII/CCl3Br-assisted single-step double functionalization of hydroxy benzaldehydes is reported. It involves simultaneous esterification of the aldehyde group and bromination of the aryl ring of phenolic aldehydes in one-pot. The reaction proceeds under mild conditions in the presence
不直接使用分子溴对酚类化合物进行溴化具有重要意义。本文报道了 IrIII/CCl3Br 辅助的羟基苯甲醛单步双官能化。它涉及在一锅中同时进行醛基酯化和酚醛芳环的溴化。在 445 nm 蓝光 LED 光的存在下,反应在温和条件下进行,以中等至良好的产率获得高度官能化的溴羟基苯甲酸酯。相比之下,Selectfluor 作为氧化剂只产生非溴酚酸酯。
Cationic Au(I)- and Pt(II)-Catalyzed Silylation of Alcohols Using Allylsilanes
The silylation of alcohols using allylsilanes was catalyzed by cationic Au(I) and Pt(II) species, which were prepared in situ from the metal chlorides ([AuCl(PPh3)], PtCl2) and a silver salt. TBS-, TES-, and TIPS-protections of various alcohols and carboxylic acids could be possible.