Tandem C–N coupling/Boulton–Katritzky rearrangement reactions of 3-aminoisoxazoles or 1,2,4-oxadiazol-3-amines with 2-pyridyl trifluoromethanesulfonate: a rapid access to [1,2,4]triazolo[1,5-<i>a</i>]pyridines

Xiong, Huilan; Li, Zihao; Tang, Huang; Li, He; Zhou, Wei

doi:10.1039/d2qo00514j

Cited by 5 publications

(5 citation statements)

References 27 publications

(33 reference statements)

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“…Experimentally, Pd 2 (dba) 3 /dppe was employed as a catalyst precursor, which can result in various potential resting states (see Table S1a in the Supporting Information). Calculations demonstrated that, among the considered candidates, the heterodimetallic (dppe)Pd-Cu(OAc) 2 species Md was most stable thermodynamically and thus set as the reference point in the whole mechanism.…”

Section: Resultsmentioning

confidence: 99%

Mechanistic Investigation into the Regio-Controllable Hydroallylations of Alkynes with Allylborons under Pd-Based Synergetic Catalyses

Liu

et al. 2023

J. Org. Chem.

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Density functional theory calculations were employed to investigate the Pd-catalyzed regio-selective hydroallylations of alkynes with allylborons: cooperation of Cu(OAc) 2 and dppe resulting in 1,4-dienes while combination of AdCO 2 H and PCy 3 leading to 1,5-dienes. A unified rationalization mechanism called "Lewis-acid−base-interaction promoted deprotonation/3,3-rearrangement" was proposed. Compared with the commonly reported metathesis pathway to only afford the metal-allyl intermediate, in the newly established mechanism, an additional Brønsted acid (as an initiator of the Pd 0 oxidative addition) is generated by the interaction of the allylboron (Lewis acid) B atom with the n BuOH (Lewis base) O atom, and subsequent 3,3rearrangement ensures the thermodynamic feasibility of the reaction. In addition, it was found that excess Cu(OAc) 2 plays two potential roles in the oxidative addition/alkyne insertion: (i) the participation of one AcO − of Cu(OAc) 2 ensures a large orbital overlap between the migrating H and Pd atoms, facilitating the formal AcO−H cleavage and (ii) the extra (OAc) 2 Cu•••O(carboxyl) σ-coordination indirectly contributes to the (Me)C�C(Ph) insertion into the Pd−H bond. Further analysis showed that the origin of the regioselectivity is closely related to the employed phosphorus ligand. These revealed results, which have been overlooked in the previous documents, would aid the development of new related catalytic reactions.

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Section: Resultsmentioning

confidence: 99%

Mechanistic Investigation into the Regio-Controllable Hydroallylations of Alkynes with Allylborons under Pd-Based Synergetic Catalyses

Liu

et al. 2023

J. Org. Chem.

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“…Usually a 1,2,4-triazolo[1,5-a]pyridine system is constructed via the stepwise formation of each of the heterocycles followed by functionalization. [16,17] In contrast, our proposed approach is a one-step tandem ring-opening/double ring-closing synthesis. Our method has the following advantages: At the same time, the 1,2,4-triazolo[1,5-a]pyridine fragment is often found in the structure of biologically active substances, including tubulin polymerization inhibitors and agents for therapy of neurodegenerative diseases.…”

Section: Discussionmentioning

confidence: 99%

Tandem Ring‐Opening/Double Ring‐Closing Synthesis of 1,2,4‐Triazolo[1,5‐a]pyridines from Chromone‐Containing Acrylonitriles

Chernov,

Kustin,

Pypa

et al. 2023

Adv Synth Catal

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We studied a reaction of chromone‐containing acrylonitriles and cyanoacrylates with acid hydrazides. This reaction turned out to be a method for the synthesis of salicyloyl‐substituted 1,2,4‐triazolo[1,5‐a]pyridines. The synthesis developed is a tandem ring‐opening/double ring‐closing process. This synthetic approach is characterized by low toxic solvents (ethanol, butanol) and mediator (Et3N), 37–84% yields, non‐chromatographic isolation of products, and substrate tolerance (59 examples).

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“…In a recent report, Zhou et al described an appropriate synthesis of functionalized triazolopyridines. [144] The reaction of 1,2,4-oxadiazoles or aminoisoxazoles with 2-pyridyl trifluoromethanesulfonates was induced by Pd(dba) 2 , L15 (Xantphos), and tBuOLi as base. The desired bicyclic compounds were isolated in medium to high yields (Scheme 121).…”

Section: Tricyclic Moleculesmentioning

confidence: 99%

Recent Advances in the Synthesis of Five‐membered Nitrogen Heterocycles Induced by Palladium Ions and Complexes

Molnár

2023

ChemistrySelect

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This review aims to collect and analyze recent results with respect to the use of varied palladium preparations in the synthesis of five-membered nitrogen heterocycles including condensed derivatives. Results have been selected with focus on studies of the last three years. Furthermore, a common feature of all methods treated here is that the nitrogencontaining five-membered ring is formed via ring closing of appropriate starting materials. Selected examples discussed will reveal that a plethora of products from small monocycles to condensed multi-ring systems can be successfully accessed. Major features are wide product ranges, high product yields and stereoselectivities often achieved under mild reaction conditions.

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Tandem C–N coupling/Boulton–Katritzky rearrangement reactions of 3-aminoisoxazoles or 1,2,4-oxadiazol-3-amines with 2-pyridyl trifluoromethanesulfonate: a rapid access to [1,2,4]triazolo[1,5-a]pyridines

Cited by 5 publications

References 27 publications

Mechanistic Investigation into the Regio-Controllable Hydroallylations of Alkynes with Allylborons under Pd-Based Synergetic Catalyses

Mechanistic Investigation into the Regio-Controllable Hydroallylations of Alkynes with Allylborons under Pd-Based Synergetic Catalyses

Tandem Ring‐Opening/Double Ring‐Closing Synthesis of 1,2,4‐Triazolo[1,5‐a]pyridines from Chromone‐Containing Acrylonitriles

Recent Advances in the Synthesis of Five‐membered Nitrogen Heterocycles Induced by Palladium Ions and Complexes

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