Due to their ubiquity in nature and frequent use in organic electronic materials, benzothiophenes are highly sought after. Here we set out an unprecedented procedure for the formation of ...benzothiophenes by the twofold vicinal C−H functionalization of arenes that does not require metal catalysis. This one‐pot annulation proceeds through an interrupted Pummerer reaction/3,3‐sigmatropic rearrangement/cyclization sequence to deliver various benzothiophene products. The procedure is particularly effective for the rapid synthesis of benzothiophenes from non‐prefunctionalized polyaromatic hydrocarbons (PAHs).
Thio‐fusion: Benzothiophenes are accessed from non‐prefunctionalized arenes in a one‐pot sequence involving an interrupted Pummerer reaction, 3,3‐sigmatropic rearrangement, and cyclization. The process does not require metals, proceeds by twofold C−H functionalization, and can be used to achieve the straightforward π‐extension of polyaromatic hydrocarbons.
A 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.
A metal-free, oxidative coupling of phenols with various nucleophiles, including arenes, 1,3-diketones and other phenols, is reported.
A 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.
A novel methodology for the decarboxylative Suzuki-Miyaura-type coupling of carboxylic acids with arylboronic acids has been developed.
A multicomponent copper-catalyzed enantio- and regioselective borocyanation of 1-aryl-1,3-butadienes has been developed. The method provides access to functionalized allylic nitriles in up to 90% ...yield and 94% ee and thus overcomes some of the long-standing problems associated with the enantioselective insertion of cyano groups into unsaturated organic molecules. Both boron and cyano functionalities can be used as handles for selective manipulation.
Despite 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.
Sulfonamides are prevalent in drug molecules, however, methods for functionalizing sulfonamides via S−N bond cleavage are scarce. Based on a re‐evaluation of N−Ts deprotection, we developed sulfonyl pyrroles as linchpins for sulfonamide functionalization. Sulfonyl pyrroles engage in various transformations that can proceed through chemical, electrochemical or photochemical pathways.
The 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.
The potassium salts of carboxylic acids are developed as efficient carboxylating agents through CO2 exchange. We describe these carboxylates as dual‐function reagents because they function as a ...combined source of CO2 and base/metalating agent. By using the salt of a commercially available carboxylic acid, this protocol overcomes difficulties when using CO2 gas or organometallic reagents, such as pressurized containers or strictly inert conditions. The reaction proceeds under mild conditions, does not require transition metals or other additives, and shows broad substrate scope. Through the preparation of several biologically important molecules, we show how this strategy provides an opportunity for isotope labeling with low equivalents of labeled CO2.
The potassium salt of triphenylacetic acid is developed as a combined source of CO2 and base/metalating agent. This method avoids specialized equipment and is used in the carboxylation of a range of compound classes. This provides a mechanistically distinct approach to carboxylation that has also been applied in carbon isotope labeling.
C-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.
Recent developments in the radical C-H amination of biology- and materials-oriented aromatics are summarized in this perspective.
Copper‐catalyzed borylative multicomponent reactions (MCRs) involving olefins and C−N electrophiles are a powerful tool to rapidly build up molecular complexity. The products from these reactions ...contain multiple functionalities, such as amino, cyano and boronate groups, that are ubiquitous in medicinal and process chemistry programs. Copper‐catalyzed MCRs are particularly attractive because they use a relatively abundant and non‐toxic catalyst to selectively deliver high‐value products from simple feedstocks such as olefins. In this Minireview, we explore this rapidly emerging field and survey the borylative union of allenes, dienes, styrenes and other olefins, with imines, nitriles and related C−N electrophiles.
Copper‐catalyzed borylative multicomponent couplings, involving olefins and C−N electrophiles, constitute an efficient approach to high‐value amine and nitrile products. This Minireview assesses the progress in this rapidly emerging field and surveys the borylative union of allenes, dienes, styrenes, and related olefins, with imines, nitriles, and related electrophiles.
A modular approach to underexplored, unsymmetrical 1benzothieno3,2-
b
1benzothiophene (BTBT) scaffolds delivers a library of BTBT materials from readily available coupling partners by combining a ...transition-metal free Pummerer CH-CH-type cross-coupling and a Newman-Kwart reaction. This effective approach to unsymmetrical BTBT materials has allowed their properties to be studied. In particular, tuning the functional groups on the BTBT scaffold allows the solid-state assembly and molecular orbital energy levels to be modulated. Investigation of the charge transport properties of BTBT-containing small-molecule:polymer blends revealed the importance of molecular ordering during phase segregation and matching the highest occupied molecular orbital energy level with that of the semiconducting polymer binder, polyindacenodithiophene-benzothiadiazole (PIDTBT). The hole mobilities extracted from transistors fabricated using blends of PIDTBT with phenyl or methoxy functionalized unsymmetrical BTBTs were double those measured for devices fabricated using pristine PIDTBT. This study underscores the value of the synthetic methodology in providing a platform from which to study structure-property relationships in an underrepresented family of unsymmetrical BTBT molecular semiconductors.
A modular approach to underexplored, unsymmetrical 1benzothieno3,2-
b
1benzothiophene (BTBT) scaffolds, combining a transition-metal free Pummerer CH-CH-type cross-coupling and a Newman-Kwart reaction, delivers a library of BTBT materials.
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