Regio- and Stereoselective Synthesis of Thiazole-Containing Triarylethylenes by Hydroarylation of Alkynes

Lee, Woohyeong; Shin, Chang-Hoon; Park, Soo Eun; Joo, Jung Min

doi:10.1021/acs.joc.9b01619

Cited by 30 publications

(15 citation statements)

References 67 publications

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“…Based on results from previous reports, [8,9] we propose the reaction mechanism shown in Figure 3. After coordination of the alkyne to the palladium(0) complex forms 7 , the carboxylic acid reacts to generate alkenylpalladium carboxylate 8 [18] .…”

Section: Figurementioning

confidence: 82%

“…They showed that an excess amount of furfural underwent α‐alkenylation with alkynes using a ruthenium catalyst under CO pressure at high temperature (Figure 1A). Recently, we demonstrated that a simple palladium(0)/carboxylic acid catalyst system is highly effective for alkenylation of an equimolar amount of thiophenes and electron‐deficient arenes using alkynes, which gives variously substituted alkenylated (hetero)arenes (Figure 1B) [8,9] . We expected that this palladium(0)/acid catalyst system has the potential to employ furfural for alkenylation by alkynes without excess use of substrates under mild conditions and avoid any reactions involving the reactive aldehyde group.…”

Section: Figurementioning

confidence: 99%

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Palladium/Carboxylic Acid‐catalyzed Alkenylation of Furfural and its Derivatives Using Alkynes

2020

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Section: Figurementioning

confidence: 82%

Section: Figurementioning

confidence: 99%

Palladium/Carboxylic Acid‐catalyzed Alkenylation of Furfural and its Derivatives Using Alkynes

2020

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“…3b). [49][50][51] If the hypothesis holds, reaction of a substrate that displays β-Χ/β-Η competition with P t Bu3 should give exclusive β-Χ with PCy3. Reacting the appropriate substrate (X = OMs) with both Pd(P t Bu3)2 and Pd(PCy3)2, we obtained β-Χ/β-Η competition and exclusive β-Χ products respectively, in line with the ligation state hypothesis (Fig.…”

Section: Resultsmentioning

confidence: 99%

β-X vs. β-H Elimination. Selection Rules for Chemoselectivity Enabled by Mechanistic Studies

Bogdos

Stepanović

Bismuto

et al. 2022

Preprint

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Alkylpalladium complexes are important intermediates in several industrially relevant catalytic reactions such as the Mizoroki–Heck, alkyl C–H activation and ethylene polymerisation. Beta-elimination - of either a hydride (β-Η) or a heteroatom (β-Χ) - is the most common decomposition pathway for these intermediates; this can either promote the desired reaction as in the Mizoroki–Heck reaction, or it can hinder reaction progress as in ethylene/vinyl halide co-polymerisations. Despite the importance of these elimination 15 processes, little mechanistic understanding exists with respect to the factors that control them. We present a systematic investigation of the factors governing the competition between β-Η and β-Χ in catalytically relevant alkylpalladium complexes. These results enabled us to derive selection rules which dictate ligand choice to control selectivity for either elimination. This knowledge may allow chemists to manipulate beta-eliminations in the design of chemoselective catalytic reactions for a wide range of applications.

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“…As the density functional theory (DFT) calculation performed with the DMF substrate suggested a ligand-to-ligand hydrogen transfer (LLHT) mechanism, the alkenylation of thiazole is also likely to follow the same mechanism. We have previously demonstrated an alternative regioselectivity using a Pd catalytic system (Scheme B) . The alkenyl Pd complex generated by hydropalladation underwent CMD at the C5 position of thiazole, affording the C5 alkenylation product.…”

Section: Divergent Reactions Of Five-membered Heteroarenes With Alkynesmentioning

confidence: 99%

Transition-Metal-Catalyzed Divergent C–H Functionalization of Five-Membered Heteroarenes

Jeong

Joo

2021

Acc. Chem. Res.

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Metrics & MoreArticle Recommendations CONSPECTUS: Conversion of common reactants to diverse products is a key objective of organic syntheses. Recent developments in transition-metal-catalyzed C−H functionalization have increased the interest in such conversions. Both the position of functionalization and the type of the substituent can be varied, allowing systematic diversification of common structural cores. Because five-membered heteroarenes (pyrazole, imidazole, thiazole, pyrrole, and thiophene) are ubiquitous in pharmaceuticals and organic functional materials, the selective C−H functionalization of these heterocyclic cores facilitates both the optimization of their physicochemical properties and streamlining of their preparation. In addition, the parent forms of these heterocycles are more readily available and inexpensive than any other derivatives of their families. Hence, their nondirected C−H functionalization is highly desirable. Although various regioselective reactions have been developed, many of them target the most reactive site; hence, except for some extensively studied arylation reactions, regiodivergent functionalization of two or more sites has been limited. This Account summarizes our work on the regiodivergent, nondirected C−H functionalization of five-membered heteroarenes with alkenes and alkynes. These unsaturated hydrocarbons are readily available, and all the composing atoms can be incorporated into products with high atom efficiency. Furthermore, the installed alkenyl groups can be transformed to other useful functional groups.To achieve comparable selectivity to that observed in the traditional reactions of these heteroarenes with highly electrophilic reagents and strong bases, a transition metal catalytic system was carefully devised with a more streamlined synthesis. A judicious choice of metals, ligands, acid and base additives, and solvents orchestrates divergent transformations using electronic and steric effects of the heteroarenes. Although C−H cleavage is a rate-and site-selectivity-determining step in most cases, the subsequent steps involving the formation of C−C bonds are often more critical than the other steps. For the C−H cleavage step, modulating the electronic properties of catalysts to make them electrophilic allows preferential alkenylation at the nucleophilic position. In addition, the presence of an internal base that can be exploited for concerted metalation−deprotonation of the acidic C−H bond offers alternative regioselectivity. Furthermore, we developed our own ligand system based on a conformationally rigid pyrazolonaphthyridine scaffold that enables aerobic C−H alkenylation reactions with steric control. We showed that the electronic and steric effects of heteroarenes can be further extended to chemodivergent reactions with norbornene derivatives. Depending on whether the palladacycle is formed, heteroarenes selectively undergo 1:2 annulation with norbornene derivatives and threecomponent reactions with other azoles through the Pd−norbornene adducts or Catell...

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Regio- and Stereoselective Synthesis of Thiazole-Containing Triarylethylenes by Hydroarylation of Alkynes

Cited by 30 publications

References 67 publications

Palladium/Carboxylic Acid‐catalyzed Alkenylation of Furfural and its Derivatives Using Alkynes

Palladium/Carboxylic Acid‐catalyzed Alkenylation of Furfural and its Derivatives Using Alkynes

β-X vs. β-H Elimination. Selection Rules for Chemoselectivity Enabled by Mechanistic Studies

Transition-Metal-Catalyzed Divergent C–H Functionalization of Five-Membered Heteroarenes

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