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1. Rh(II)‐catalyzed Intermolecular Benzylic C(sp ³ )−H Alkylation of Methyl‐substituted Arenes by N ‐Aryl‐α‐diazo‐β‐amidoesters

   https://doi.org/10.1002/cctc.202101977  

   Yuan, Shaoren; McLaren, Eric_J; France, Stefan (March 2022, ChemCatChem)

   Abstract Herein, a general approach to intermolecular benzylic C(sp³)−H alkylation of methyl‐substituted arenes is reported using metal carbenes derived fromN‐aryl‐α‐diazo‐β‐amidoesters and dirhodium catalysts. Alkylated products were formed in up to 81 % yield with demonstrated functional group tolerance, outpacing previous literature. The unique amide‐ester scaffolding can be exploited through various derivatizations for broad synthetic utility and provides a starting point for the development of selectivity rules and reactivity profiles for these intermolecular C(sp³)−H functionalizations. 

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2. Synthesis of Heterocycles by HNTf2-Catalyzed C–H Functionalization of Vinyldiazo Compounds with 3-Phenyl-3-hydroxyisoindolinone

   https://doi.org/10.1055/a-2360-8359  

   Bao, Ming; Arman, Hadi; Doyle, Michael P (July 2024, Synthesis)

   Abstract A Brønsted acid catalyzed C–H functionalization of vinyldiazoacetates with 3-hydroxyisoindolinone is developed. This methodology provides a general access to E-substituted isoindolinone vinyldiazo compounds in good yields and excellent diastereoselectivities with broad substrate generality under mild conditions, and with 4-substituted 2-diazo-3-butenoates produces fused bicyclic pyrrolidines. The reaction generally involves addition of the N-acyl ketiminium electrophile, formed from the 3-hydroxyisoindolinone, to the vinylogous position of the vinyldiazo compound resulting in vinyldiazonium ion intermediates that undergo deprotonation to new vinyldiazo compounds or ring closure to fused bicyclic pyrrolidines. 

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3. A Conjugate Addition Approach to Diazo‐Containing Scaffolds with β Quaternary Centers

   https://doi.org/10.1002/anie.202004557  

   Fang, Jian; Howard, Evan M.; Brewer, Matthias (May 2020, Angewandte Chemie International Edition)

   Abstract Structurally complex diazo‐containing scaffolds are formed by conjugate addition to vinyl diazonium salts. The electrophile, a little studied α‐diazonium‐α,β‐unsaturated carbonyl compound, is formed at low temperature under mild conditions by treating β‐hydroxy‐α‐diazo carbonyls with Sc(OTf)₃. Conjugate addition occurs selectively at the 3‐position of indole to give α‐diazo‐β‐indole carbonyls, and enoxy silanes react to give 2‐diazo‐1,4‐dicarbonyl products. These reactions result in the formation of tertiary and quaternary centers, and give products that would be otherwise difficult to form. Importantly, the diazo functional group is retained within the molecule for future manipulation. Treating an α‐diazo ester indole addition product with Rh₂(OAc)₄caused a rearrangement to occur to give a 2‐(1H‐indol‐3‐yl)‐2‐enoate. In the case of diazo ketone compounds, this shift occurred spontaneously on prolonged exposure to the Lewis acidic reaction conditions. 

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4. Copper( i )-catalyzed highly enantioselective [3 + 3]-cycloaddition of γ-alkyl enoldiazoacetates with nitrones

   https://doi.org/10.1039/D0QO00539H  

   Dong, Kuiyong; Xu, Xinfang; Doyle, Michael P. (June 2020, Organic Chemistry Frontiers)

   null (Ed.)

   Chiral copper( i ) catalysts are preferred over chiral dirhodium( ii ) catalysts for [3 + 3]-cycloaddition reactions of γ-alkyl-substituted enoldiazoacetates compounds with nitrones. Using the In-SaBox ligand these reactions effectively produce cis -3,6-dihydro-1,2-oxazine derivatives under mild conditions in high yield and with exceptional stereocontrol, and enantioselectivity increases with the size of the γ-substituent. Mechanistic studies show that cycloaddition occurs solely through the formation of ( Z )-γ-substituted metallo-enolcarbene intermediates that are catalytically gennerated from both ( Z )- and ( E )-γ-substituted enoldiazoactates via donor–acceptor cyclopropene intermediates. 

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5. Non-Aufbau orbital ordering and spin density modulation in high-spin donor–acceptor conjugated polymers

   https://doi.org/10.1039/d2cp02355e  

   Sabuj, Md Abdus; Muoh, Obinna; Huda, Md Masrul; Rai, Neeraj (October 2022, Physical Chemistry Chemical Physics)

   High-spin ground-state organic materials with unique spin topology can significantly impact molecular magnetism, spintronics, and quantum computing devices. However, strategies to control the spin topology and alignment of the unpaired spins in different molecular orbitals are not well understood. Here, we report modulating spin distribution along the molecular backbone in high-spin ground-state donor–acceptor (D–A) conjugated polymers. Density functional theory calculations indicate that substitution of different heteroatoms (such as C, Si, N, and Se) alters the aromatic character in the thiadiazole unit of the benzobisthiadiazole (BBT) acceptor and modulates the oligomer length to result in high-spin triplet ground-state, orbital and spin topology. The C, Si, and Se atom substituted polymers show a localized spin density at the two opposite ends of the polymers. However, a delocalized spin distribution is observed in the N substituted polymer. We find that the hybridization (sp 3 vs. sp 2 ) of the substituent atom plays an important role in controlling the electronic structure of these materials. This study shows that atomistic engineering is an efficient technique to tune the spin topologies and electronic configurations in the high-spin ground-state donor–acceptor conjugated polymers, compelling synthetic targets for room-temperature magnetic materials. 

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