1,720,984 research outputs found
Aromatic C-H amination: a radical approach for adding new functions into biology-and materials-oriented aromatics
No full textC-H amination is the most powerful method to directly add nitrogen functionalities into a variety of arenes including biology- and materials-oriented molecules. Recent developments in aromatic C-H amination chemistry have enabled the conversion of unactivated arenes into a range of arylamine derivatives without using directing groups or excess amounts of arenes. The key for such successful transformations is the catalytic generation of nitrogen or arene radical intermediates. In this perspective, we discuss recent developments in the radical C-H amination of aromatic molecules. We believe the resulting arylamines, which are hitherto difficult to access, will exhibit unexplored functions for biological and materials application.</p
Late-stage sulfonic acid/sulfonate formation from sulfonamides via sulfonyl pyrroles
No full textSulfonamides are present in a range of useful molecules, such as drugs and agrochemicals. In recent years, the functionalization of sulfonamides via S–N bond cleavage has received increased attention. In this report, we detail an accessible and low-cost route for transforming primary sulfonamides into the corresponding sulfonic acids/sulfonates via sulfonyl pyrroles. The reaction is demonstrated with a range of substrates including aryl and alkyl sulfonamides, and in the late-stage functionalization of several sulfonamide-containing drug molecules.</p
Sulfur(IV) in Transition-Metal-Free Cross-Couplings for Biaryl Synthesis
No full textThe reactivity of sulfur(IV) compounds is of great current interest among organic chemists. In this Perspective, we discuss the chemistry of sulfur(IV) (namely, sulfoxides, sulfonium salts, and sulfinates) within the area of transition-metal-free cross-couplings for biaryl synthesis. These sulfur(IV)-based methods show potential in sustainable biaryl formation and can deliver unique biaryl structures that are difficult to access by other means. This Perspective also highlights how the versatile reactivity of sulfur(IV) has helped design new reagents, mediators, and catalysts.</p
Recent Progress in Decarboxylative Oxidative Cross-Couplings for Biaryl Synthesis
No full textThe beginning of the 21st century has seen a tremendous growth in the field of decarboxylative activation. Benzoic acids are now recognised as atom-economicalternatives to traditional cross-coupling partners and they also benefit from being inexpensive, readily-available and shelfstable reagents. In this microreview, we discuss recent developments in the coupling of benzoic acids with either anarene or a second benzoic acid, a process often labelled as decarboxylative oxidative cross-coupling. These procedures hold great promise for the development of highly selective and atom-economic cross-couplings
Sulfonium-aided coupling of aromatic rings via sigmatropic rearrangement
Full text linkBiaryl synthesis continues to occupy a central role in chemical synthesis. From blockbuster drug molecules to organic electronics, biaryls present numerous possibilities and new applications continue to emerge. Transition-metal-catalyzed coupling reactions represent the gold standard for biaryl synthesis and the mechanistic steps, such as reductive elimination, are well established. Developing routes that exploit alternative mechanistic scenarios could give unprecedented biaryl structures and expand the portfolio of biaryl applications. We have developed metal-free C–H/C–H couplings of aryl sulfoxides with phenols to afford 2-hydroxy-2′-sulfanylbiaryls. This cascade strategy consists of an interrupted Pummerer reaction and [3,3] sigmatropic rearrangement. Our method enables the synthesis of intriguing aromatic molecules, including oligoarenes, enantioenriched dihetero[8]helicenes, and polyfluorobiaryls. From our successes in aryl sulfoxide/phenol couplings and a deeper understanding of sigmatropic rearrangements for biaryl synthesis, we have established related methods, such as aryl sulfoxide/aniline and aryl iodane/phenol couplings. Overall, our fundamental interests in underexplored reaction mechanisms have led to various methods for accessing important biaryl architectures
Enantio- and diastereoselective synthesis of homopropargyl amines by copper-catalyzed coupling of imines, 1,3-enynes, and diborons
No full textAn efficient, enantio- and diastereoselective, copper-catalyzed coupling of imines, 1,3-enynes, and diborons is reported. The process shows broad substrate scope and delivers complex, chiral homopropargyl amines; useful building blocks on the way to biologically-relevant compounds. In particular, functionalized homopropargyl amines bearing up to three contiguous stereocenters can be prepared in a single step.</p
Para-coupling of phenols with C2/C3-substituted benzothiophene S-oxides
No full textC2 and C3 substituted benzothiophenes are common structures in medicinal and materials chemistry. The cross-coupling of phenols with benzothiophenes is a useful route towards these important molecules. In this report we reveal an efficient C–H/C–H-type cross-coupling of benzothiophenes, activated as their S-oxides, with phenols to give C2/C3 arylated benzothiophenes. Whereas previous reports describe cross-coupling at the ortho-position between phenols and sulfoxides, this procedure allows para-functionalization of phenols that typically have their ortho positions blocked.</p
Sulfoxide-mediated oxidative cross-coupling of phenols
No full textA metal-free, oxidative coupling of phenols with various nucleophiles, including arenes, 1,3-diketones and other phenols, is reported. Cross-coupling is mediated by a sulfoxide which inverts the reactivity of the phenol partner. Crucially, the process shows high selectivity for cross-versus homo-coupling and allows efficient access to a variety of aromatic scaffolds including biaryls, benzofurans and, through an iterative procedure, aromatic oligomers.</p
Primary Sulfonamide Functionalization via Sulfonyl Pyrroles: Seeing the N−Ts Bond in a Different Light
No full textDespite common occurrence in molecules of value, methods for transforming sulfonamides are distinctly lacking. Here we introduce easy-to-access sulfonyl pyrroles as synthetic linchpins for sulfonamide functionalization. The versatility of the sulfonyl pyrrole unit is shown by generating a variety of products through chemical, electrochemical and photochemical pathways. Preliminary results on the direct functionalization of primary sulfonamides are also provided, which may lead to new modes of activation.</p
Decarboxylative Suzuki-Miyaura Coupling of (hetero)aromatic carboxylic acids using Iodine as the Terminal Oxidant
Full text linkA novel methodology for the decarboxylative Suzuki-Miyaura-type coupling has been established. This process uses iodine or a bromine source as both the decarboxylation mediator and the terminal oxidant, thus avoiding the need for stoichiometric amounts of transition metal salts previously required. Our new protocol allows for the construction of valuable biaryl architectures through the coupling of (hetero)aromatic carboxylic acids with arylboronic acids. The scope of this decarboxylative Suzuki reaction has been greatly diversified, allowing for previously inaccessible non-ortho-substituted aromatic acids to undergo this transformation. The procedure also benefits from low catalyst loadings and the absence of stoichiometric transition metal additives
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