Dealkenylative Ni-Catalyzed Cross-Coupling Enabled by Tetrazine and Photoexcitation

Chen, Sicong; Zhu, Qi; Cao, Yuhui; Li, Chen; Guo, Yinliang; Kong, Lingran; Che, Jinteng; Guo, Zhixian; Chen, Han; Zhang, Nan; Fang, Xianhe; Lu, Jia‐Tian; Luo, Tuoping

doi:10.1021/jacs.1c05092

Cited by 21 publications

(20 citation statements)

References 53 publications

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“… 67 , 68 Sulfone 57 further illustrates the structural and functional diversity accessible from a single such platform. 69 , 70 In this context, it is of note that compound 56 is a commercially available yet expensive building block, 71 − 73 which the new route is able to deliver on scale and, if desirable, in labeled format. Extrapolation of the chemistry shown in Scheme 8 to the other (spirocyclic) products containing isopropenyl (or related alkenyl) substituents described above should give access to a multitude of valuable scaffolds for medicinal chemistry and chemical biology.…”

Section: Resultsmentioning

confidence: 99%

C–H Insertion via Ruthenium Catalyzed gem-Hydrogenation of 1,3-Enynes

et al. 2022

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gem -Hydrogenation of an internal alkyne with the aid of [Cp*RuCl] 4 as the precatalyst is a highly unorthodox transformation, in which one C atom of the triple bond is transformed into a methylene group, whereas the second C atom gets converted into a ruthenium carbene. In the case of 1,3-enynes bearing a propargylic steering substituent as the substrates, the reaction occurs regioselectively, giving rise to vinyl carbene complexes that adopt interconverting η 1 /η 3 -binding modes in solution; a prototypical example of such a reactive intermediate was characterized in detail by spectroscopic means. Although both forms are similarly stable, only the η 3 -vinyl carbene proved kinetically competent to insert into primary, secondary, or tertiary C–H bonds on the steering group itself or another suitably placed ether, acetal, orthoester, or (sulfon)amide substituent. The ensuing net hydrogenative C–H insertion reaction is highly enabling in that it gives ready access to spirocyclic as well as bridged ring systems of immediate relevance as building blocks for medicinal chemistry. Moreover, the reaction scales well and lends itself to the formation of partly or fully deuterated isotopologues. Labeling experiments in combination with PHIP NMR spectroscopy (PHIP = parahydrogen induced polarization) confirmed that the reactions are indeed triggered by gem -hydrogenation, whereas kinetic data provided valuable insights into the very nature of the turnover-limiting transition state of the actual C–H insertion step.

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Section: Resultsmentioning

confidence: 99%

C–H Insertion via Ruthenium Catalyzed gem-Hydrogenation of 1,3-Enynes

et al. 2022

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“…Dihydropyridines and related partially saturated nitrogen heterocycles can demonstrate divergent reactivity under blue light compared to that of under dark reaction conditions. Such compounds are weak reductants in the absence of light and typically act as excellent H-atom donors. − In contrast to this, under blue light, their excited state can serve as a strong single-electron reductant. ,− This ability to act as a strong reductant under blue light conditions have been used in Ni-catalyzed cross-coupling reactions to generate alkyl radicals and to reduce Ni complexes. ,− On the other hand, in Ni-catalyzed cross-coupling reactions of aryl halides with electrophiles, reduction of the initial oxidative addition product, L-Ni(II)(Ar)(X) species, to an L-Ni(I)Ar can be a rate-determining step, as this step is a heterogeneous reaction occurring at the interface of solution/Zn (X = halide). ,− …”

Section: Resultsmentioning

confidence: 99%

Light-Promoted Dearomative Cross-Coupling of Heteroarenium Salts and Aryl Iodides via Nickel Catalysis

2022

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Partially saturated nitrogen heterocycles are versatile building blocks for the preparation of other nitrogen heterocycles. For example, dihydropyridines can be converted to pyridines, tetrahydropyridines, and piperidines through oxidation, reduction, and functionalization reactions, respectively. Dearomatization of heteroarenes is an attractive approach for the synthesis of partially saturated heterocycles such as dihydropyridines due to the wide availability of heteroarenes. Significant research efforts have been dedicated to the addition of nucleophiles to various heteroarenium salts in this direction using organoboron or organometallic reagents. The availability of organoboron and organometallic coupling partners has been an important limitation to this chemistry. Direct coupling of electrophiles with heteroareniums could significantly improve the scope of these dearomatization reactions due to the wider availability of electrophiles compared to nucleophiles such as organoboron and organometallic reagents. Herein, we report the coupling of aryl iodides with pyridinium and related heteroarenium salts catalyzed by Ni/bpp and an Ir photocatalyst using Zn as a terminal reductant. This methodology tolerates a wide range of functional groups and allows the coupling of aryl and heteroaryl iodides, thus significantly expanding the scope of nitrogen heterocycle scaffolds that could be prepared through dearomatization of heteroarenes. The reaction products have been further functionalized to prepare various nitrogen heterocycles. Initial mechanistic studies indicate that the reaction described herein goes through a unique mechanism involving dimers of dihydroheteroarenes.

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“…As expected, the reaction occurred smoothly using C1 as the catalyst in the presence of an atmosphere of oxygen, leading to the diketone product 7 in a significantly improved yield (74%, entry 9). The effect of the solvent on the reaction was next investigated (entries [10][11][12][13][14]. Compared to the use of DCE, THF, or CH 3 CN as the reaction solvent, alcohols proved to be better choices with EtOH as the optimal one (entry 9).…”

Section: Resultsmentioning

confidence: 99%

“…9,10 In the literature precedents, such a transformation was generally realized through alkene ozonolysis followed by metal-induced β-fragmentation of alkoxy radicals (Scheme 1B), which was initially disclosed by Schreiber 11 and recently expanded by Kwon et al 12 In addition, a recent work by Luo and co-workers revealed that a cycloaddition/photoirradiation process was able to break the alkyl and alkene C(sp 3 )–C(sp 2 ) linkage, affording the alkyl radical for further bond formation. 13 Here, we wish to report our discovery of the first HAT-mediated C(sp 3 )–C(sp 2 ) bond cleavage which represents a new method for the preparation of ketones from alkenes.…”

Section: Introductionmentioning

confidence: 99%