Nickel‐Catalyzed Conversion of Enol Triflates into Alkenyl Halides

Hofstra, Julie L.; Poremba, Kelsey E.; Shimozono, Alex; Reisman, Sarah E.

doi:10.1002/ange.201906815

Cited by 19 publications

(9 citation statements)

References 45 publications

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“…in 82% yield. 13 In parallel, naphthoquinone 18 8d was converted to the desired bromoaldehyde 13 through a reduction (Na 2 S 2 O 4 )/MOM protection (MOMCl, i-Pr 2 NEt) sequence in 82% overall yield, as shown in Scheme 1. Vinyl iodide 14 was then treated with tertbutyllithium in the presence of TMEDA, and to the sogenerated cyclohexenyllithium intermediate was added aldehyde 13, affording secondary alcohol 20 (73% yield, inconsequential mixture of diastereoisomers), whose exposure to NMO/TPAP cat.…”

Section: Resultsmentioning

confidence: 99%

Total Synthesis of the Monomeric Unit of Lomaiviticin A

Nicolaou

Chen

et al. 2020

J. Am. Chem. Soc.

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The architecturally symmetrical and synthetically challenging marine natural products lomaiviticins A and B present alluring synthetic targets due to their molecular complexity, potent antitumor properties, and natural scarcity. Herein, we report the total synthesis of the fully glycosylated monomeric unit of lomaiviticin A, monolomaiviticin A. The retrosynthetically derived synthetic strategy relied on an intramolecular palladium-catalyzed coupling reaction to complete the tetracyclic aglycon scaffold and gold-promoted glycosylations to install the synthetically challenging αand β-glycoside moieties of the target molecule. This accomplishment paves a path for the eventual total synthesis of lomaiviticins A and B and opens opportunities for biological investigations within this family of compounds.

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Section: Resultsmentioning

confidence: 99%

Total Synthesis of the Monomeric Unit of Lomaiviticin A

Nicolaou

Chen

et al. 2020

J. Am. Chem. Soc.

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“…53 The low conversion of substrate 135 under the reductive Heck cyclization suggested that oxidative addition of Ni(0) with the vinyl triflate moiety was sluggish in the presence of the free C7 alcohol. While efforts to enhance the reactivity by adding phosphine or pyridine-type ligands were unfruitful, we were inspired by Reisman's recent work on the Ni-catalyzed conversion of vinyl triflates to vinyl halides 54 in which the addition of LiBr significantly boosted the conversion of a vinyl triflate substrate (138), surpassing the effects of chloride and iodide. To our delight, in this complex reductive Heck cyclization/homoallylic elimination process, the addition of excess LiBr salt indeed resulted in full conversion of 135 and yielded the desired products in 69% yield (Scheme 20B).…”

Section: ■ Introductionmentioning

confidence: 99%

Asymmetric Total Synthesis of (+)-Phainanoid A and Biological Evaluation of the Natural Product and Its Synthetic Analogues

et al. 2023

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Here, we report our detailed efforts toward the synthesis of phainanoids, a novel class of dammarane-type triterpenoids with potent immunosuppressive activities and unique structural features. Systematic model studies have been carried out, and efficient approaches have been established to construct the benzofuranone-based 4,5-spirocycle, the D/E/F tricyclic core, the [4.3.1] propellane, and the 5,5-oxaspirolactone moieties. The asymmetric synthesis of (+)-phainanoid A has been achieved through kinetic resolution of the tricyclic core followed by diastereoselective installation of the A/B/C and G/H rings and fragment coupling with the enantioenriched I/J rings. In addition, novel estrone-derived phainanoid analogues have been prepared. The immunosuppressive and cell survival assays revealed that (+)-phainanoid A and some of its synthetic analogues can specifically inhibit stimulation-induced lymphocyte proliferation but not cell survival at their effective concentrations. Preliminary structure–activity relationship information has been obtained, which could inspire future design of immunosuppressive phainanoid analogues.

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“…The signal is analogous to the one obtained by Reisman while monitoring the Ni-catalyzed triflate-iodide exchange reaction of enol ethers (see the Supporting Information for details). 21 Although insights on the exact structure of the active Ni(I) catalyst are still elusive given that it evaded isolation, the in situ EPR experiments further support the Ni(I) hypothesis (see the Supporting Information for details). Based on the above experiments, we speculate It should be pointed out that the mechanism in Scheme 1, although plausible, remains purely speculative at present.…”

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confidence: 99%

“…This species appears at high concentration and slowly fades away as the reaction progresses. The signal is analogous to the one obtained by Reisman while monitoring the Ni-catalyzed triflate-iodide exchange reaction of enol ethers (see the Supporting Information for details) 21. Although insights on the exact structure of the active Ni(I) catalyst are still elusive given that it evaded isolation, the in situ EPR experiments further support the Ni(I) hypothesis (see the Supporting Information for details).…”

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confidence: 99%