CHEMRedox ICP 2019 INVITED TALKS Code: CHEMRedox_I1 Presenter: Eun Jin Cho (KOR) Abstract Title: Visible-Light-Induced Synthesis of Heterocycles Co-Author(s): Vineet Soni, Youngmin You Abstract: Development of practical and selective routes to important building units is a main goal in synthetic chemistry, thus eventually enabling facile access to even complex functional molecules. Since halogens are the most widely used precursors in organic reactions, the development of building blocks containing halogens, especially those with two different halogens in a single step (hitherto unprecedented), will be highly beneficial. We synthesized a new class of heterocyclic building blocks, 4-bromo-2-fluoroquinolines, utilizing halogen bond complex formation under visible light irradiation. The utility of the new di-halogenated building blocks was demonstrated in several applications, including the synthesis of an anti-cancer drug candidate, by exploiting the differential reactivity of the –F and –Br groups in the coupling reaction. In addition, we demonstrated an unprecedented approach for the generation of iminyl radicals via a photocatalytic energy transfer process from readily available heterocyclic precursors. This method is distinctive to the previous photoinduced electron transfer approaches to N-centered radicals. In combination with singlet oxygen, the in situ generated nitrogen radical undergoes a selective ipso-addition to arenes to furnish remotely double functionalized spiro-azalactam products. The scope of substrates was explored with the mechanistic elucidation to include the computational studies. Institution: Chung-Ang University Code: CHEMRedox_I2 Presenter: Steve Marsden (GBR) Abstract Title: Photochemically-Mediated Direct Aromatic C-H Amination: A Tool for Molecular Innovation Co-Author(s): Professor John Plane, Dr Sebastian Abstract: Aromatic amines are key components of a range of effect chemicals both natural and man-made, and methods for their construction Cosgrove, Dr Tanya Bykova are therefore in high demand: ca. 5% of all reactions carried out in the pharmaceutical industry are aimed at this motif. Existing synthetic approaches are typically multi-step and/or involve the use of expensive precious-metal catalysts and pre-functionalised starting materials. An attractive alternative would be involve direct functionalisation of aromatic C-H bonds to introduce the amine group in a single transformation. We have investigated the direct amination of aromatic C-H bonds using photochemically-generated amininium radicals, and further developed conditions whereby direct ‘one-pot’ conversion of secondary amines to their arylated derivatives is achieved by in situ activation [1]. The reactions can be carried out in batch or continuous flow mode, the latter facilitating simple gram-scale production [2]. Mechanistic studies, supported by DFT calculations, shed light upon the pathways involved in the amination reactions. The highly reactive aminium radicals allow access to unusual highly three-dimensional scaffolds which have properties suitable for fragment-based drug discovery and screening programmes as well as target synthesis. In this presentation we will describe our advances in these areas. [1] Chemical Science, 2018, 9, 6647-6652; [2] ChemPhotoChem, 2018, 2, 851-854. Institution: School of Chemistry, University of Leeds Code: CHEMRedox_I3 Presenter: Daniele Leonori (GBR) Abstract Title: Use of Nitrogen Radicals in Remote Functionalizations Co-Author(s): n/a Abstract: The selective functionalization of unactivated sp3 carbons streamlines access to molecules that can be difficult to prepare using classical disconnections. Radical strategies are powerful platforms to achieve this goal owing to the ability of odd-electron species to undergo fast transposition reactions. Nitrogen-radicals are versatile synthetic intermediates to achieve this goal. However, the difficulties associated with their generation have somewhat thwarted their use in synthetic chemistry.[1] We have developed a class of easy-to-make oximes and hyroxy-amides that upon photoredox oxidation enable access to iminyl and amidyl radicals.[2,3] These species have been used in radical transposition reactions thus enabling the site-selective functionalization of unactivated sp3-carbons. In particular, we have harnessed the ability of cyclic iminyl radicals to undergo ring-opening reactions. Following radical functionalization has enabled the preparation of remotely-functionalized nitriles. In the case of the amidyl radicals, we have exploited their ability to undergo efficient 1,5-HAT in order to target the gamma-functionalization of amides and the delta- functionalization of protected amines. These strategies have been applied to the deconstruction–functionalization of complex steroids and to the preparation of unnatural aminoacids. [1] S. Z. Zard, Chem. Soc. Rev. 2008, 37, 1603. [2] Chem. Eur. J. 2018, 24, 12154. [3] Angew. Chem. Int. Ed. 2017, 56, 13361. [4] Angew. Chem. Int. Ed. 2018, 57, 744. [5] Angew. Chem. Int. Ed. 2018, 57, 12495. Institution: School of Chemistry, University of Manchester Code: CHEMRedox_I4 Presenter: Tanja Cuk (USA) Abstract Title: Resolving Chemical Bond Dynamics at an Electrode Surface Co-Author(s): Daniel Aschaffenburg and Xihan Chen Abstract: Catalytic mechanisms at electrode surfaces guide the development of electrochemically-controlled energy storing reactions and chemical synthesis. The intermediate steps of these mechanisms are challenging to identify in real time, but are critical to understanding the speed, stability, and selectivity of product evolution. In my group, we employ photo-triggered vibrational and electronic spectroscopy to time-resolve the catalytic cycle at a surface, identifying meta-stable intermediates and critical transition states which connect one to another. The talk will focus on the highly selective water oxidation reaction at the semiconductor (SrTiO3)- aqueous interface, triggered by an ultrafast light pulse in an electrochemical cell. Here, I will describe the dynamics from the birth of the initial intermediates that trap charge (Ti-O• and Ti-O•-Ti) through the next event, suggested to be the formation of the first O-O bond of O2 evolution. The dynamics of charge screening at the interface, a hallmark of electrochemically controlled reactions, will be addressed in both aqueous and non-aqueous (battery) electrolytes. While many open questions remain, these experiments provide and benchmark the opportunity to quantify intermediates at an electrode surface and their associated dynamics. Institution: University of Colorado, Boulder and RASEI Code: CHEMRedox_I5 Presenter: Scott C. Warren (USA) Abstract Title: Quantum-confined Superlattices of 2D Materials for Photochemistry Co-Author(s): Tyler Farnsworth, Adam Woomer Abstract: Two-dimensional semiconductors offer many useful properties, but these properties are often lost when the 2D materials are restacked into electrically conductive 3D solids. Here we show that 2D semiconductors self-assemble with small molecules to yield 3D superlattices in which the desirable optical, electronic, and vibrational characteristics of the 2D semiconductor are preserved. Structural analysis reveals that the 2D semiconductor is separated by monolayers of small molecules. This separation is just large enough to induce quantum-confined properties within each 2D semiconductor, but just small enough to facilitate tunneling between 2D semiconductors. As a result, the 3D superlattices have high electrical conductivity, reaching over 1 mS/cm. Our simulations illustrate the principles that underly self-assembly and reveal how these materials generalize to many unique compositions that facilitate explorations of novel photoredox chemistry. Institution: University of North Carolina at Chapel Hill CONTRIBUTED TALKS Code: CHEMRedox_T1 Presenter: Max Kudisch (USA) Abstract Title: The Role of Speciation and Photoexcitation of Ni-amine Complexes in Light-driven C-N Cross Coupling Reactions Co-Author(s): Chern-Hooi Lim, Garret M. Miyake Abstract: C–N cross coupling reactions between aryl halides and amines are vital to produce substituted anilines which are important motifs in bioactive compounds. Heat-driven Pd catalysis represents the most developed method to date for constructing C–N bonds and commonly proceeds through a Pd(0)/Pd(II) mechanistic cycle. Recently, Ni catalysis has emerged as a sustainable alternative to Pd that can more readily proceed via radical mechanisms to access a different scope of products. Under light irradiation, dual catalytic Ni/photoredox catalyst (PC) systems have enabled C–N cross coupling with a wide substrate scope under mild conditions. We have recently reported (JACS, 2018, 140 (24), 7667–7673) a Ni-catalyzed C-N cross-coupling methodology in which the Ni-amine complex operates without requiring an added PC. We have employed this process for the synthesis of diverse C-N coupled products (40 examples, including the drug flibanserin) by irradiating a solution containing an amine, an aryl halide, and a catalytic amount of NiBr2•3H2O with a 365 nm LED at room temperature. Excess amine substrate serves as ligand and base. Density functional theory calculations support a mechanistic cycle in which direct photoexcitation of the Ni-amine complex leads to photoinduced electron transfer, forming an amino radical that reacts with the Ni complex or aryl halide to furnish the product. Additional mechanistic studies have revealed that different amine coupling