Palladium-Catalyzed Desilylative Acyloxylation of Silicon–Carbon Bonds on (Trimethylsilyl)arenes: Synthesis of Phenol Derivatives from Trimethylsilylarenes
摘要:
A strategy for desilylative acetoxylation of (trimethylsilyl)-arenes has been developed in which (trimethylsilyl)arenes are converted into acetoxyarenes. The direct acetoxylation is performed in the presence of 5 mol % of Pd(OAc)(2) and PhI(OCOCF3)(2) (1.5 equiv) in AcOH at 80 degrees C for 17 h. The acetoxyarenes are obtained in good to high yields (67-98%). The synthetic utility is demonstrated with a one-pot transformation of (trimethylsilyearenes to phenols by successive acetoxylation and hydrolysis. Furthermore, desilylative acyloxylation of 2-(trimethylsilyl)-naphthalene using several carboxylic acids has been conducted.
directing group in C–H bond-functionalization reactions, reductive removal of this directing group is not straightforward. Currently available methods are limited to nickel-catalyzed reactions using i PrMgX or hydrosilane as a reductant, leaving the functional group compatibility issue to be solved. Herein, we report rhodium-catalyzed reductivecleavage of aryl carbamates using i PrOH as a milder reductant
尽管在 C-H 键官能化反应中广泛使用氨基甲酸酯作为导向基团,但还原去除该导向基团并不简单。目前可用的方法仅限于使用 i PrMgX 或氢硅烷作为还原剂的镍催化反应,留下官能团兼容性问题有待解决。在此,我们报告了使用 i PrOH 作为更温和的还原剂对氨基甲酸芳基酯进行铑催化的还原裂解。
Gold-Catalysed Oxyarylation of Styrenes and Mono- and<i>gem</i>-Disubstituted Olefins Facilitated by an Iodine(III) Oxidant
作者:Liam T. Ball、Guy C. Lloyd-Jones、Christopher A. Russell
DOI:10.1002/chem.201103061
日期:2012.3.5
1‐Hydroxy‐1,2‐benziodoxol‐3(1H)‐one (IBA) is an efficient terminal oxidant for gold‐catalysed, three‐component oxyarylation reactions. The use of this iodine(III) reagent expands the scope of oxyarylation to include styrenes and gem‐disubstituted olefins, substrates that are incompatible with the previously reported Selectfluor‐based methodology. Diverse arylsilane coupling partners can be employed
Silyloxyarenes as Versatile Coupling Substrates Enabled by Nickel-Catalyzed C–O Bond Cleavage
作者:Eric M. Wiensch、David P. Todd、John Montgomery
DOI:10.1021/acscatal.7b02025
日期:2017.9.1
coupling processes. The C(sp2)–O bond of aryl silyl ethers is directly transformed into C–H or C–Si bonds using Ti(O-i-Pr)4 or trialkylsilanes as reagents using nickel catalysts with N-heterocyclic carbene (NHC) ligands. Paired with the useful characteristics of silyl protecting groups, these methods enable protected hydroxyls to directly participate in high-value bond-forming steps rather than requiring
甲硅烷氧基芳烃在各种镍催化的偶联过程中被证明是一类通用的底物。使用Ti(O- i -Pr)4将芳基甲硅烷基醚的C(sp 2)-O键直接转变为CH-H或C-Si键或三烷基硅烷作为试剂,使用具有N-杂环卡宾(NHC)配体的镍催化剂。这些方法与甲硅烷基保护基团的有用特性相结合,使受保护的羟基直接参与高价值的键形成步骤,而不需要常规方法所需的脱保护活化策略。甲硅烷基氧芳烃的这些过程提供了与广泛使用的酚衍生物(例如新戊酸芳基酯,氨基甲酸酯和甲基醚)互补的反应性,因此能够在不保护基团和不活化基团的情况下,对复杂的底物进行化学选择性衍生化提供强大的策略。
Addition and Cyclization Reactions in the Thermal Conversion of Hydrocarbons with an Enyne Structure, 5. High-Temperature Ring Closures of 1,3-Hexadien-5-ynes to Naphthalenes – Competing Reactions via Isoaromatics, Alkenylidene Carbenes, and Vinyl-type Radicals
2-ethynylstyrenes 7a–c were subjected to high-temperature pyrolysis. The cycloisomerization products isolated suggest that these are formed by three competing processes: by (i) an electrocyclic or a molecule-induced, (ii) an alkenylidenecarbene controlled, and (iii) a radical-controlled ring-closure process. To estimate the relative importance of these three reactions here mentioned, the substrates have
Structurally diverse arylchlorides were silylated with sodium silylsilanolate reagents in the presence of a Ni(cod)2 catalyst complexed with a phosphine ligand; PMe2Ph for electron-rich substrates, and PCy2Ph for electron-deficient ones. The mild reaction conditions allowed the silylation of various arylchlorides including functionalised drug molecules.