Rapid Deoxyfluorination of Alcohols with N-Tosyl-4-chlorobenzenesulfonimidoyl Fluoride (SulfoxFluor) at Room Temperature

The deoxyfluorination of alcohols is a fundamentally important approach to access alkyl fluorides, and thus the development of shelf-stable, easy-to-handle, fluorine-economical, and highly selective deoxyfluorination reagents is highly desired. This work describes the development of a crystalline compound, N-tosyl-4-chlorobenzenesulfonimidoyl fluoride (SulfoxFluor), as a novel deoxyfluorination reagent that possesses all of the aforementioned merits, which is rare in the arena of deoxyfluorination. Endowed by the multi-dimensional modulating ability of the sulfonimidoyl group, SulfoxFluor is superior to 2-pyridinesulfonyl fluoride (PyFluor) in fluorination rate, and is also superior to perfluorobutanesulfonyl fluoride (PBSF) in fluorine-economy. Its reaction with alcohols not only tolerates a wide range of functionalities including the more sterically hindered alcoholic hydroxyl groups, but also exhibits high fluorination/elimination selectivity. Because SulfoxFluor can be easily prepared from inexpensive materials and can be safely handled without special techniques, it promises to serve as a practical deoxyfluorination reagent for the synthesis of various alkyl fluorides.     

Main-Group Metal Complexes in Selective Bond Formations Through Radical Pathways

Recent years have witnessed remarkable advances in radical reactions involving main-group metal complexes. This includes the isolation and detailed characterization of main-group metal radical compounds, but also the generation of highly reactive persistent or transient radical species. A rich arsenal of methods has been established that allows control over and exploitation of their unusual reactivity patterns. Thus, main-group metal compounds have entered the field of selective bond formations in controlled radical reactions. Transformations that used to be the domain of late transition-metal compounds have been realized, and unusual selectivities, high activities, as well as remarkable functional-group tolerances have been reported. Recent findings demonstrate the potential of main-group metal compounds to become standard tools of synthetic chemistry, catalysis, and materials science, when operating through radical pathways.     

Insights into the Mechanism of Gold(I) Oxidation with Aryldiazonium Salts

In the last decade, aryldiazonium salts have attracted interest as coupling partners in cross-coupling reactions mediated by gold. Initially, the presence of a photocatalyst and a light source was needed to achieve gold oxidation with these electrophiles. However, recently, it has been shown that in some instances just heating, light irradiation, or the addition of certain bases and/or nucleophiles is enough. In this review, the transformations developed so far using aryldiazonium salts as electrophiles are summarized with special emphasis on mechanistic studies. The information gained by different authors, indicates that the specific steps of gold oxidation with aryldiazonium salts depends upon the activation mode of the diazonium salt.     

天然水体中可溶性有机质的自由基光化学行为

可溶性有机质在天然水体中广泛分布,是全球碳循环的重要组成部分。大部分的可溶性有机质含有苯环、羧基、羟基和羰基等发色团,能够吸收特定波长的太阳光,产生水合电子、单线态氧、羟基自由基等活性自由基,从而影响天然水体污染物的光化学转化以及降解过程。本文综述了20世纪90年代以来可溶性有机质的自由基光化学行为以及其在水体污染物转化中的作用方面的研究进展,并探讨了今后研究中应该关注的问题。     

Selective Aerobic Oxygenation of Tertiary Allylic Alcohols with Molecular Oxygen

Aerobic epoxidation of tertiary allylic alcohols remains a significant challenge. Reported here is an efficient and highly chemoselective copper‐catalyzed epoxidation and semipinacol rearrangement reaction of tertiary allylic alcohols with molecular oxygen. The solvent 1,4‐dioxane activates dioxygen, thereby precluding the addition of a sacrificial reductant.     

Visible‐Light‐Induced Efficient Selective Oxidation of Nonactivated Alcohols over {001}‐Faceted TiO2 with Molecular Oxygen

In the presence of molecular oxygen, a {001}‐faceted nanocrystalline anatase TiO₂ catalyst enabled the selective oxidation of nonactivated aliphatic alcohols to the corresponding aldehydes or ketones under visible light. The reaction shows excellent conversion and selectivity towards the formation of the carbonyl products without over‐oxidation to the corresponding carboxylic acids. The exceptional reactivity of the catalyst is possibly due to the absorption of visible light originating from a stronger interaction of alcohol with the {001} facet, which facilitates the modification of the band structure of TiO₂, thus facilitating the photogenerated hole transfer and subsequent oxidation processes. The experimental results have also been corroborated by first‐principles quantum chemical DFT calculations.     

Selective Generation of Formamides through Photocatalytic CO2 Reduction Catalyzed by Ruthenium Carbonyl Compounds

The selective formation of dialkyl formamides through photochemical CO₂ reduction was developed as a means of utilizing CO₂ as a C₁ building block. Photochemical CO₂ reduction catalyzed by a [Ru(bpy)₂(CO)₂]²⁺ (bpy: 2,2′‐bipyridyl)/[Ru(bpy)₃]²⁺/Me₂NH/Me₂NH₂⁺ system in CH₃CN selectively produced dimethylformamide. In this process a ruthenium carbamoyl complex ([Ru(bpy)₂(CO)(CONMe₂)]⁺) formed by the nucleophilic attack of Me₂NH on [Ru(bpy)₂(CO)₂]²⁺ worked as the precursor to DMF. Thus Me₂NH acted as both the sacrificial electron donor and the substrate, while Me₂NH₂⁺ functioned as the proton source. Similar photochemical CO₂ reductions using R₂NH and R₂NH₂⁺ (R=Et, nPr, or nBu) also afforded the corresponding dialkyl formamides (R₂NCHO) together with HCOOH as a by‐product. The main product from the CO₂ reduction transitioned from R₂NCHO to HCOOH with increases in the alkyl chain length of the R₂NH. The selectivity between R₂NCHO and HCOOH was found to depend on the rate of [Ru(bpy)₂(CO)(CONR₂)]⁺ formation.     

Copper Photoredox Catalyzed A3’ Coupling of Arylamines,Terminal Alkynes,and Alcohols through a Hydrogen Atom Transfer Process

The first successful example of the three‐component coupling of N‐alkylanilines, terminal alkynes, and alcohols was achieved at room temperature by a visible‐light‐mediated copper‐catalyzed photoredox hydrogen‐atom transfer process. This method allows preparation of propargylamines through uniquely selective α‐C?H bond activation of unactivated alkylalcohols. Preliminary studies indicate that formation of α‐oxy radical is operative. This approach facilitates rapid access to biologically important propargylamines from methanol as an abundant feedstock.     

Rapid Interception of CnF2n+1(O)SO. Radical with Copper-Based Carbene: A Novel Access to Perfluoroalkanesulfinate Ester

In this communication, an unprecedented interception of C_nF_2n+1(O)SO^. radical with a copper-based carbene has been established. Distinguished by wide substrate scopes and mild reaction conditions, this novel radical–carbene coupling reaction (RCC reaction) provides a fundamentally different and mechanistically interesting strategy for the synthesis of perfluoroalkanesulfinate esters.     

自由基修饰共轭微孔聚合物应用于5-羟甲基糠醛选择性氧化

采用有机单体侧链嫁接2,2,6,6-四甲基哌啶氧自由基（2,2,6,6-tetramethylpiperidineoxyl,TEMPO）的策略将TEMPO嫁接到2,5-二溴苯甲酸侧链,并与四（4-乙炔基苯）甲烷通过Sonogashira偶联反应,构筑TEMPO自由基功能化共轭微孔聚合物CMP-4-TEMPO.利用核磁共振谱（NMR）、扫描电子显微镜（SEM）、粉末X-射线衍射（XRD）红外吸收光谱（FT-IR）和电子顺磁共振谱（EPR）等技术研究了所合成单体及CMP形貌和结构.催化性能测试结果表明CMP-4-TEMPO可将5-羟甲基糠醛（5-HMF）高效、高选择性氧化成高附加值2,5-二甲酰基呋喃（2,5-DFF）.CMP-4-TEMPO催化剂循环利用10次仍保持较高的转化率.提出了CMP-4-TEMPO中形成TEMPO氧正离子是实现5-HMF转化为2,5-DEF的催化氧化机理.CMP-4-TEMPO有望成为各种醇高效、高选择性氧化以及可循环利用的异相催化剂.     

Photocatalysis with Quantum Dots and Visible Light: Selective and Efficient Oxidation of Alcohols to Carbonyl Compounds through a Radical Relay Process in Water

Selective oxidation of alcohols to aldehydes/ketones has been achieved with the help of 3‐mercaptopropionic acid (MPA)‐capped CdSe quantum dot (MPA‐CdSe QD) and visible light. Visible‐light‐prompted electron‐transfer reaction initiates the oxidation. The thiyl radical generated from the thiolate anion adsorbed on a CdSe QD plays a key role by abstracting the hydrogen atom from the C−H bond of the alcohol (R¹CH(OH)R²). The reaction shows high efficiency, good functional group tolerance, and high site‐selectivity in polyhydroxy compounds. The generality and selectivity reported here offer a new opportunity for further applications of QDs in organic transformations.     

Selective Aerobic Oxidation of Primary Alcohols to Aldehydes over Nb2O5 Photocatalyst with Visible Light

Primary alcohols are selectively converted into aldehydes by using a Nb₂O₅ photocatalyst under visible‐light irradiation. A strong interaction between the alcohol and Nb₂O₅ generates a donor level within the forbidden band of Nb₂O₅, which provides a visible‐light‐harvesting ability. Over oxidation of aldehydes into carboxylic acids does not proceed under visible‐light irradiation.     

金属卟啉/MgAl水滑石催化醇选择性氧化制备羰基化合物

将MgAl水滑石引入到金属四苯基卟啉(MTPPs,M=Co,Fe,Mn,Ni)催化氧化体系中,实现了醇的选择性氧化。 结果表明,在分子氧/异丁醛体系中,CoTPP在苯甲醇氧化制苯甲醛反应中表现出优异的催化活性,MgAl水滑石添加剂可有效地提高醛的选择性。 在苯甲醇1 mmol、乙腈2 mL、CoTPP 5 mg、MgAl水滑石18 mg、异丁醛5 mmol、反应温度60 ℃、氧气气氛下反应2 h,苯甲醇的转化率和苯甲醛的选择性分别达到94%和92%。 另外,此催化体系在其它醇类化合物的氧化反应中也具有较好催化活性。     

Microwave Assisted Selective Oxidation of Benzylic Alcohols with Calcium Hypochlorite under Solvent-Free Conditions

Summary.  A remarkably fast microwave assisted selective oxidation of benzylic alcohols with calcium hypochlorite under solvent-free conditions is described. Received August 28, 2000. Accepted September 21, 2000