Accelerated Discovery of Energy Transfer-Catalyzed Dearomative Cycloadditions through a Data-Driven Three-Layer Screening Strategy.

Visible-light-mediated energy transfer (EnT) photocatalysis has emerged as a highly appealing strategy for converting planar (hetero)arenes into complex, medicinally relevant, three-dimensional (3D) architectures. Current methodologies for intermolecular dearomative photocycloadditions, however, are restricted to bicyclic (hetero)aromatic systems, while the more abundant monocyclic (hetero)arenes remain vastly underexplored. Accessing the triplet state of the ubiquitous monocyclic (hetero)arenes poses a formidable challenge due to their high triplet energy barriers.

Electrochemical Synthesis of Disubstituted Alkynes from Dihydrazones.

A simple, straightforward, scalable, and sustainable electrochemical transformation of dihydrazones to alkynes via anodic oxidation has been developed. The protocol operates under galvanostatic conditions in a commercially available undivided cell utilizing reusable carbon-based electrodes. This methodology enables the efficient synthesis of a broad range of alkynes with moderate to excellent yield.

A General Three-Component Nozaki-Hiyama-Kishi-Type Reaction Enabled by Delayed Radical-Polar Crossover.

Nozaki-Hiyama-Kishi (NHK) reactions offer a mild approach for the formation of alcohol motifs through radical-polar crossover-based pathways from various radical precursors. However, the application of multicomponent NHK-type reactions, which allow the formation of multiple bonds in a single step, has been largely restricted to bulky alkyl radical precursors, thus limiting their expanded utilization. Herein, we disclose a general three-component NHK-type reaction enabled by delayed radical-polar crossover, which efficiently tolerates a plethora of radical precursors that were previously unavailable.

Solvent-Dependent Divergent Cyclization of Bicyclo[1.1.0]butanes.

Bicyclo[1.1.0]butanes (BCBs) have recently garnered significant research interest as versatile precursors for synthesizing potential [n.

Ring expansion of indene by photoredox-enabled functionalized carbon-atom insertion.

Skeletal editing has received unprecedented attention as an emerging technology for the late-stage manipulation of molecular scaffolds. The direct achievement of functionalized carbon-atom insertion in aromatic rings is challenging. Despite ring-expanding carbon-atom insertion reactions, such as the Ciamician-Dennstedt re-arrangement, being performed for more than 140 years, only a few relevant examples of such transformations have been reported, with these limited to the installation of halogen, ester and phenyl groups.

γ-Amino Alcohols via Energy Transfer Enabled Brook Rearrangement.

In the long-standing quest to synthesize fundamental building blocks with key functional group motifs, photochemistry in the recent past has comprehensively established its attractiveness. Amino alcohols are not only functionally diverse but are ubiquitous in the biologically active realm of compounds. We developed bench-stable bifunctional reagents that could then access the sparsely reported γ-amino alcohols directly from feedstock alkenes through energy transfer (EnT) photocatalysis.

Double Strain-Release [2π+2σ]-Photocycloaddition.

In pursuit of potent pharmaceutical candidates and to further improve their chemical traits, small ring systems can serve as a potential starting point. Small ring units have the additional merit of loaded strain at their core, making them suitable reactants as they can capitalize on this intrinsic driving force. With the introduction of cyclobutenone as a strained precursor to ketene, the photocycloaddition with another strained unit, bicyclo[1.

Photoredox-Enabled Dearomative [2π + 2σ] Cycloaddition of Phenols.

Dearomative photocycloaddition of monocyclic arenes is an appealing strategy for comprehending the concept of "escape from flatland". This brings the replacement of readily available planar aromatic hydrocarbon units with a 3D fused bicyclic core with -enriched carbon units. Herein, we outline an intermolecular approach for the dearomative photocycloaddition of phenols.

Energy transfer photocatalysis: exciting modes of reactivity.

Excited (triplet) states offer a myriad of attractive synthetic pathways, including cycloadditions, selective homolytic bond cleavages and strain-release chemistry, isomerizations, deracemizations, or the fusion with metal catalysis. Recent years have seen enormous advantages in enabling these reactivity modes through visible-light-mediated triplet-triplet energy transfer catalysis (TTEnT). This tutorial review provides an overview of this emerging strategy for synthesizing sought-after organic motifs in a mild, selective, and sustainable manner.

Combinatorial Ligand Assisted Simultaneous Control of Axial and Central Chirality in Highly Stereoselective C-H Allylation.

The significance of stereoselective C-H bond functionalization thrives on its direct application potential to pharmaceuticals or complex chiral molecule synthesis. Complication arises when there are multiple stereogenic elements such as a center and an axis of chirality to control. Over the years cooperative assistance of multiple chiral ligands has been applied to control only chiral centers.

-Selective Difunctionalization of Bicyclobutanes Enabled by Photoredox-Mediated C-S σ-Bond Scission.

Given the importance of cyclic frameworks in molecular scaffolds and drug discovery, it is intriguing to precisely forge and manipulate ring systems in synthetic chemistry. In this field, the intermolecular synthesis of densely substituted cyclobutanes with precise diastereocontrol under simple reaction conditions remains a challenge. Herein, a photoredox strategy for the difunctionalization of bicyclo[1.

Dearomative ring expansion of thiophenes by bicyclobutane insertion.

Skeletal ring enlargement is gaining renewed interest in synthetic chemistry and has recently focused on insertion of one or two atoms. Strategies for heterocyclic expansion through small-ring insertion remain elusive, although they would lead to the efficient formation of bicyclic products. Here, we report a photoinduced dearomative ring enlargement of thiophenes by insertion of bicyclo[1.

-Selective Dearomative [2π + 2σ] Photocycloadditions of Bicyclic Aza-Arenes.

Dearomative photocycloadditions are valuable chemical transformations, serving as an efficient platform to create three-dimensional molecular complexity. However, the photolability of the original addition product especially within the context of cycloadditions often causes undesired consecutive rearrangements, rendering these cycloadducts elusive. Herein, we report an -selective intermolecular photocycloaddition of bicyclic aza-arenes including (iso)quinolines, quinazolines, and quinoxalines by utilizing a strain-release approach.

Hatemongers ride on echo chambers to escalate hate speech diffusion.

Recent years have witnessed a swelling rise of hateful and abusive content over online social networks. While detection and moderation of hate speech have been the early go-to countermeasures, the solution requires a deeper exploration of the dynamics of hate generation and propagation. We analyze more than 32 million posts from over 6.

EnT-Mediated N-S Bond Homolysis of a Bifunctional Reagent Leading to Aliphatic Sulfonyl Fluorides.

Sulfur(VI) fluoride exchange (SuFEx) gives rise to a plethora of high-valent sulfur linkages; however, the availability of (aliphatic) sulfonyl fluoride manifolds lag behind, owing to the limited sources of introducing the SOF moiety via a classical two-electron approach. Recently, radical-based methodologies have emerged as a complementary strategy to increase the diversity of accessible click partners. In this work, synthesis of a bench-stable sulfamoyl fluoride reagent is presented, which may undergo sigma-bond homolysis upon visible-light-induced sensitization to form protected β-amino sulfonyl fluorides from alkene feedstocks.

Chromium/Photoredox Dual Catalyzed Synthesis of α-Benzylic Alcohols, Isochromanones, 1,2-Oxy Alcohols and 1,2-Thio Alcohols.

Herein, a Cr/Photoredox-catalyzed general synthetic strategy to access α-benzylic alcohols, isochromanones, oxy alcohols and thio alcohols is unveiled. Alkylation of aldehydes being a crucial C-C bond forming reaction, designing competent catalytic systems would render an attractive and decorated set of diverse alcohol motifs. Considering the challenges associated with classical organometallic chemistry, the strategy of dual catalysis is applied here to generate diverse alcohol motifs in a mild and efficient manner.

Intermolecular [2π+2σ]-photocycloaddition enabled by triplet energy transfer.

For more than one century, photochemical [2+2]-cycloadditions have been used by synthetic chemists to make cyclobutanes, four-membered carbon-based rings. In this reaction, typically two olefin subunits (two π-electrons per olefin) cyclize to form two new C-C σ-bonds. Although the development of photochemical [2+2]-cycloadditions has made enormous progress within the last century, research has been focused on such [2π+2π]-systems, in which two π-bonds are converted into two new σ-bonds.

Transition metal catalyzed C-H bond activation by -metallacycle intermediates.

-Metallacycles have become the key reaction intermediates in activating various remote C(sp)-H and C(sp)-H bonds in the past decade and aided in achieving unusual site-selectivity. Various novel -chelating auxiliaries have assisted metals to reach desired remote C-H bonds of different alcohol and amine-derived substrates. As a result, a wide range of organic transformations of C-H bonds like halogenation, acetoxylation, amidation, sulfonylation, olefination, acylation, arylation, were accessible using the -metallacycle strategy.

Accessing C2-Functionalized 1,3-(Benz)azoles through Transition Metal-Catalyzed C-H Activation.

The skeletal presence of 1,3-azoles in a variety of bioactive natural products, pharmacophores, and organic materials demands the derivatization of such heteroarenes regioselectively. Plenty of cross-coupling as well as cyclocondensation reactions have been performed to build up these skeletons but remained commercially unrealizable. A couple of severe drawbacks are faced by these traditional protocols that require a more straightforward strategy to obviate them.

Cobalt-Catalyzed C(sp)-H Allylation of Biphenyl Amines with Unbiased Terminal Olefins.

Unactivated olefins usually react poorly in conventional alkenylation reactions. Their introduction via C-H activation is limited to aromatic acids. Herein, we disclose a C-H functionalization protocol of aromatic amines with unactivated olefins, which shows exclusive allylic selectivity for the distal ring of the biphenyl system by exploiting a readily available cobalt(II) catalyst.

Cloning and Expression of Phytase appA Gene from Shigella sp. CD2 in Pichia pastoris and Comparison of Properties with Recombinant Enzyme Expressed in E. coli.

The phytase gene appAS was isolated from Shigella sp. CD2 genomic library. The 3.