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1. A cheap metal catalyzed ring expansion/cross-coupling cascade: a new route to functionalized medium-sized and macrolactones

   https://doi.org/10.1039/d2sc06157k  

   Liu, Shuai; Ma, Pengchen; Zhang, Lu; Shen, Shenyu; Miao, Hong-Jie; Liu, Le; Houk, K. N.; Duan, Xin-Hua; Guo, Li-Na (May 2023, Chemical Science)

   A Cu or Fe-catalyzed radical ring expansion/coupling cascade was developed. It provides a new access to medium-sized and macrolactones with CN, N₃, SCN, and X groups. DFT calculations suggest a Cu(i)/Cu(ii)/Cu(iii) catalytic cycle for the cyanation. 

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2. Uncovering a CF ₃ Effect on X‐ray Absorption Energies of [Cu(CF ₃ ) ₄ ] ⁻ and Related Copper Compounds by Using Resonant Diffraction Anomalous Fine Structure (DAFS) Measurements**

   https://doi.org/10.1002/anie.202313744  

   Alayoglu, Pinar; Chang, Tieyan; Yan, Connly; Chen, Yu‐Sheng; Mankad, Neal P. (November 2023, Angewandte Chemie International Edition)

   Abstract Understanding the electronic structures of high‐valent metal complexes aids the advancement of metal‐catalyzed cross coupling methodologies. A prototypical complex with formally high valency is [Cu(CF₃)₄]⁻(1), which has a formal Cu(III) oxidation state but whose physical analysis has led some to a Cu(I) assignment in an inverted ligand field model. Recent examinations of1by X‐ray spectroscopies have led previous authors to contradictory conclusions, motivating the re‐examination of its X‐ray absorption profile here by a complementary method, resonant diffraction anomalous fine structure (DAFS). From analysis of DAFS measurements for a series of seven mononuclear Cu complexes including1, here it is shown that there is a systematic trifluoromethyl effect on X‐ray absorption that blue shifts the resonant Cu K‐edge energy by 2–3 eV per CF₃, completely accounting for observed changes in DAFS profiles between formally Cu(III) complexes like1and formally Cu(I) complexes like (Ph₃P)₃CuCF₃(3). Thus, in agreement with the inverted ligand field model, the data presented herein imply that1is best described as containing a Cu(I) ion with dⁿcount approaching 10. 

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3. δ C–H (hetero)arylation via Cu-catalyzed radical relay

   https://doi.org/10.1039/c8sc04366c  

   Zhang, Zuxiao; Stateman, Leah M.; Nagib, David A. (January 2019, Chemical Science)

   null (Ed.)

   A Cu-catalyzed strategy has been developed that harnesses a radical relay mechanism to intercept a distal C-centered radical for C–C bond formation. This approach enables selective δ C–H (hetero)arylation of sulfonamides via intramolecular hydrogen atom transfer (HAT) by an N-centered radical. The radical relay is both initiated and terminated by a Cu catalyst, which enables incorporation of arenes and heteroarenes by cross-coupling with boronic acids. The broad scope and utility of this catalytic method for δ C–H arylation is shown, along with mechanistic probes for selectivity of the HAT mechanism. A catalytic, asymmetric variant is also presented, as well as a method for accessing 1,1-diaryl-pyrrolidines via iterative δ C–H functionalizations. 

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4. Suzuki‐Miyaura Cross‐Coupling of Amides using Well‐Defined, Air‐Stable [(PR ₃ ) ₂ Pd(II)X ₂ ] Precatalysts

   https://doi.org/10.1002/adsc.202000122  

   Ma, Siyue; Zhou, Tongliang; Li, Guangchen; Szostak, Michal (April 2020, Advanced Synthesis & Catalysis)

   Abstract A versatile method for the Suzuki‐Miyaura cross‐coupling of amides using highly active, well‐defined, and air‐stable Pd−phosphine precatalysts is reported. Most notably, the method represents the first example of using practical and operationally‐simple Pd(II)−phosphine precatalysts in the emerging amide bond cross‐coupling manifold. The reactions are efficient at 0.10 mol% loading, furnishing biaryl ketones with high chemoselectivity for N−C(O) bond cleavage. This versatile method enables for the first time to achieve Pd−phosphine‐catalyzed cross‐coupling of amides at ppm loading. This C−N cross‐coupling can be used to efficiently furnish pharmaceutical intermediates by orthogonal Pd‐catalyzed cross‐couplings. We fully expect that operationally‐simple [(PR₃)₂Pd(II)X₂] precatalysts as effective triggers for N−C(O) cross‐coupling will be of broad synthetic and catalytic interest. magnified image 

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5. N -Butylpyrrolidone (NBP) as a non-toxic substitute for NMP in iron-catalyzed C(sp ² )–C(sp ³ ) cross-coupling of aryl chlorides

   https://doi.org/10.1039/D1GC02377B  

   Bisz, Elwira; Koston, Martina; Szostak, Michal (October 2021, Green Chemistry)

   Although iron catalyzed cross-coupling reactions show extraordinary promise in reducing the environmental impact of more toxic and scarce transition metals, one of the main challenges is the use of reprotoxic NMP (NMP = N -methylpyrrolidone) as the key ligand to iron in the most successful protocols in this reactivity platform. Herein, we report that non-toxic and sustainable N -butylpyrrolidone (NBP) serves as a highly effective substitute for NMP in iron-catalyzed C(sp 2 )–C(sp 3 ) cross-coupling of aryl chlorides with alkyl Grignard reagents. This challenging alkylation proceeds with organometallics bearing β-hydrogens with efficiency superseding or matching that of NMP with ample scope and broad functional group tolerance. Appealing applications are demonstrated in the cross-coupling in the presence of sensitive functional groups and the synthesis of several pharmaceutical intermediates, including a dual NK1/serotonin inhibitor, a fibrinolysis inhibitor and an antifungal agent. Considering that the iron/NMP system has emerged as one of the most powerful iron cross-coupling technologies available in both academic and industrial research, we anticipate that this method will be of broad interest. 

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