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1. Diastereoconvergent synthesis of anti -1,2-amino alcohols with N-containing quaternary stereocenters via selenium-catalyzed intermolecular C–H amination

   https://doi.org/10.1039/d2sc02648a  

   Zheng, Tianyi; Berman, Janna L.; Michael, Forrest E. (August 2022, Chemical Science)

   We report a diastereoconvergent synthesis of anti -1,2-amino alcohols bearing N-containing quaternary stereocenters using an intermolecular direct C–H amination of homoallylic alcohol derivatives catalyzed by a phosphine selenide. Destruction of the allylic stereocenter during the selenium-catalyzed process allows selective formation of a single diastereomer of the product starting from any diastereomeric mixture of the starting homoallylic alcohol derivatives, eliminating the need for the often-challenging diastereoselective preparation of starting materials. Mechanistic studies show that the diastereoselectivity is controlled by a stereoelectronic effect (inside alkoxy effect) on the transition state of the final [2,3]-sigmatropic rearrangement, leading to the observed anti selectivity. The power of this protocol is further demonstrated on an extension to the synthesis of syn -1,4-amino alcohols from allylic alcohol derivatives, constituting a rare example of 1,4-stereoinduction. 

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2. N -Acyl pyrroles: chemoselective pyrrole dance vs. C–H functionalization/aroylation of toluenes

   https://doi.org/10.1039/D1QO00944C  

   Wang, Huan; Mao, Jianyou; Shuai, SuJuan; Chen, Shuguang; Zou, Dong; Walsh, Patrick J.; Li, Jie (October 2021, Organic Chemistry Frontiers)

   Chemoselectivity is one of the most challenging issues facing the chemical sciences. In this study, the first highly chemoselective reactions of N -acylpyrroles via either an anionic Fries rearrangement (pyrrole dance) or a C–H functionalization of toluene to provide aryl benzyl ketones are advanced. This efficient and operationally simple approach enables the synthesis of either 2-aroylpyrroles or aryl benzyl ketones in good to excellent yields under transition metal-free conditions. The choice of base plays a crucial role in controlling the chemoselectivity. The aroylation of toluene derivatives was observed with N -acylpyrroles when subjected to KN(SiMe 3 ) 2 , while anionic Fries rearrangement products were produced with LiN(SiMe 3 ) 2 . Surprisingly, cross-over experiments indicate that the anionic Fries rearrangement is an intermolecular process. The aroylation reaction has the advantage over Weinreb amide chemistry in that it does not require preformed organometallic reagents or cryogenic temperatures. 

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3. Imino‐λ ³ ‐iodane and Catalytic Amount of I ₂ ‐Mediated Synthesis of N ‐Allylsulfenamides via [2,3]‐Sigmatropic Rearrangement

   https://doi.org/10.1002/ejoc.202000961  

   Makitalo, Cody_L; Yoshimura, Akira; Rohde, Gregory_T; Mironova, Irina_A; Yusubova, Rosa_Y; Yusubov, Mekhman_S; Zhdankin, Viktor_V; Saito, Akio (October 2020, European Journal of Organic Chemistry)

   A facile metal‐free [2,3]‐sigmatropic rearrangement reaction of allyl sulfides viaN‐sulfilimine intermediates has been developed. Treatment of allyl sulfides with imino‐λ³‐iodanes in the presence of a catalytic amount of elemental iodine allowed the reaction to proceed under mild conditions and gave the correspondingN‐allylsulfenamide compounds in moderate to good yields. SeveralN‐allylsulfenamide structures have been confirmed by single‐crystal X‐ray crystallography. The reaction initially involves the sulfonylimino group transfer reaction between imino‐λ³‐iodane and the sulfur atom, resulting in the formation ofN‐sulfilimine species, followed by [2,3]‐sigmatropic rearrangement to form theN‐allylsulfenamide. 

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4. Attenuating N ‐Oxyl Decomposition for Improved Hydrogen Atom Transfer Catalysts

   https://doi.org/10.1002/anie.202315917  

   Yang, Cheng; Farmer, Luke_A; McFee, Elvis_C; Jha, Rahul_Kant; Maldonado, Stephen; Pratt, Derek_A; Stephenson, Corey_R_J (April 2024, Angewandte Chemie International Edition)

   Abstract The design ofN‐oxyl hydrogen atom transfer catalysts has proven challenging to date. Previous efforts have focused on the functionalization of the archetype, phthalimide‐N‐oxyl. Driven in part by the limited options for modification of this structure, this strategy has provided only modest improvements in reactivity and/or solubility. Our previous mechanistic efforts suggested that while the electron‐withdrawing carbonyls of the phthalimide are necessary to maximize the O−H bond dissociation enthalpy of the HAT product hydroxylamine and overall reaction thermodynamics, they undergo nucleophilic substitution leading to catalyst decomposition. In an attempt to minimize this vulnerability, we report the characterization ofN‐oxyl catalysts wherein the aryl ring in PINO is replaced with the combination of a substituted heteroatom and quaternary carbon. By rendering one carbonyl carbon less electrophilic and the other less sterically accessible, the correspondingN¹‐aryl‐hydantoin‐N³‐oxyl radical showed significantly higher stability than PINO as well as a modest improvement in reactivity. This proof‐of‐principle in new scaffold design may accelerate future HAT catalyst discovery and development. 

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5. Dimensional Reduction Guides Electronic Structure Evolution in the A _n Cu _4–n SnS ₄ Semiconductor Series

   https://doi.org/10.1021/jacs.5c07366  

   Viti, Michael A; Li, Zhi; Wolverton, Christopher; Kanatzidis, Mercouri G (August 2025, Journal of the American Chemical Society)

   The search for new functional materials with tunable properties remains a central challenge in chemistry, particularly for applications in energy and electronics. In this work, we present a framework for predictive crystal design in alkali metal chalcogenides that enables controlled dimensional reduction of a parent covalent motif, yielding a broad range of electronic structures, which systematically evolve from one parent to the other. We present 11 new members of the AnCu4–nSnS4 family (A = alkali metal; n = 0–4), which reduce the three-dimensional (3D) covalent network of Cu4SnS4 into various 3D, 2D, 1D, and 0D [Cu4–nSnS4]n− motifs through the substitution of Cu with alkali metals of various radii. The end members of the family set the range in achievable band gaps at 0.99 eV for fully covalent Cu4SnS4 (n = 0) and 3.38 eV for K4SnS4 (n = 4) with 0D [SnS4]n− tetrahedra. As the dimensionality of [Cu4–nSnS4]n− systematically reduces within AnCu4–nSnS4 (n = 1–3), a stepwise increase in band gap energy occurs through a gradual decrease in the energy of the valence band maximum and an increase in the conduction band minimum, with an increase in the effective masses of charge carriers. Furthermore, irrespective of the alkali metal, the thermal stability decreases with decreasing [Cu4–nSnS4]n− dimensionality within the quaternary members. Most importantly, we demonstrate that predictable crystal structure and property evolution for a given composition space is possible by deriving a general formula based on substituting the covalent metals of a parent structure with alkali metals. 

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