UiO‐66 microcrystals catalyzed direct arylation of enol acetates and heteroarenes with aryl diazonium salts in water

Abstract

UiO‐66 is a classic Metal–organic framework (MOF) that constructed by zirconium cations and terephthalate with high chemical and thermal stability. Using pristine UiO‐66 nanocrystals as the catalysts, the carbon–carbon bond formation based on denitrogenative substitution of aryl diazonium salts has been achieved under mild condition. The C–H arylation of both enol acetates and heteroarenes could be performed in aqueous medium without other metal assistance. The UiO‐66 catalyst shows good water stability and reusability as well as impressive functional group tolerance.

Dyedauxiliary Group Strategy for the α-Functionalization of Ketones and Esters

“… 18 − 20 Among the suitable precursors of aryl radicals made active under photoredox catalysis conditions, the class of aryl diazonium salts is the most preferred, and the reaction was carried out in the presence of Ru(II)-based complexes ( Scheme 1 , path a), 21 porphyrins (path b), 22 and organic dyes 23 in the role of photocatalyst. It should be noticed, however, that the same reaction was found to occur in discrete to good yields also under thermal conditions, by using either salicylic acid 24 or a UiO-66 metal organic framework 25 as the promoters.…”

“…α-Aryl carbonyls are structural motifs present in both natural and synthetic bioactive products (e.g., the antiplatelet agent Prasugrel), − whose synthesis has been, in the 20th century, an exclusive domain of transition-metal-catalyzed processes, − with the only exception represented by the (thermal- or photoinitiated) S RN 1 coupling of aryl halides with aggressive enolate anions , and the arylation of enol silyl ethers via photogenerated triplet aryl cations (in turn obtained only from 4-chloro and 4-fluoroanilines). , However, the recent bursting of visible light photoredox-catalyzed processes has changed dramatically the way-of-thinking of organic chemistry practitioners. , In such an approach, a thermally stable substrate is activated under mild conditions, by a photoexcited catalyst via a monoelectronic oxidation/reduction step, to generate a high-energy intermediate (e.g., a radical or a radical ion) able to react with a coupling partner. − In this regard, the trapping of a photogenerated aryl radical by an enolate derivative (mainly enol acetates) has emerged as one of the most proposed strategies to achieve α-arylated carbonyls. − Among the suitable precursors of aryl radicals made active under photoredox catalysis conditions, the class of aryl diazonium salts is the most preferred, and the reaction was carried out in the presence of Ru­(II)-based complexes (Scheme , path a), porphyrins (path b), and organic dyes in the role of photocatalyst. It should be noticed, however, that the same reaction was found to occur in discrete to good yields also under thermal conditions, by using either salicylic acid or a UiO-66 metal organic framework as the promoters.…”

Synthesis and Application of Task-Specific Bimetal–Organic Frameworks in the Synthesis of Biological Active Spiro-Oxindoles

“…catalysts. 32,33 The cornerstone of click chemistry involves the formation of a triazole ring, typically composed of an azide group and a triple bond. Consequently, incorporating an azide group into the desired MOF structure becomes pivotal.…”

“…Click chemistry has emerged as one of the most effective methodologies for synthesizing organic compounds and diverse catalysts, garnering substantial attention from scientists and industries over the past decade. , Utilizing click chemistry facilitates the modification of the structure of Metal–Organic Frameworks (MOFs), converting them into targeted and efficient catalysts for both catalytic and photocatalytic applications. − Diazonium salts play a crucial role in advancing the click chemistry of MOFs, as they enable the creation of various electrophilic and nucleophilic systems, leading to the design and synthesis of MOF-based catalysts. , The cornerstone of click chemistry involves the formation of a triazole ring, typically composed of an azide group and a triple bond. Consequently, incorporating an azide group into the desired MOF structure becomes pivotal.…”