HfCl<sub>4</sub>-Catalyzed [4 + 2] Cycloaddition of β,γ-Unsaturated α-Keto Esters with Alkynes

Duan, Depeng; Qiu, Huixin; Tang, Mengdie; Song, Ran; Wen, Shengyou; Yang, Daoshan; Lv, Jian

doi:10.1021/acs.joc.2c00007

Cited by 5 publications

(3 citation statements)

References 39 publications

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“…So, Duan and coworkers in 2022 described a Lewis‐acid HfCl 4 ‐catalyzed [4+2]‐cycloaddition for the synthesis of polysubstituted 4 H ‐pyrans 271 from β , γ ‐unsaturated α ‐keto esters 269 and various symmetric or unsymmetric alkynes 270 via a vinyl carbocation under mild conditions in good yields with excellent regioselectivity (Scheme 75). [223] Mechanistically, α ‐keto ester initially coordinated to the Lewis‐acid catalyst HfCl 4 . The addition of the alkyne to the γ ‐carbon atom of the activated α ‐keto ester CLXII via TS‐XVI gave the vinyl carbocation Int‐ CLXIII .…”

Section: Introductionmentioning

confidence: 99%

Transition‐Metal Catalyzed [4+2]‐Cycloaddition Reactions: A Sexennial Update

Panda,

Mohapatra,

Ansar Ahemad

et al. 2024

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Cycloaddition reactions serve as exceptionally useful strategy to provide atom‐economical, efficient and practical access to complex molecules from simple starting materials. The [4+2]‐cycloaddition reaction allows for the stereospecific construction of six‐membered carbo‐/heterocycles. Cycloaddition reactions catalyzed by transition metals are potent methods for the rapid construction of highly functionalized molecular frameworks. This review article summarizes the different reports on transition‐metal catalyzed [4+2]‐cycloaddition reactions involving various transition metals such as Pd, Cu, Rh, Au, Fe, Ni, Sc, Sn, Hf, Ag, Mn, Dy, Co etc. for the straightforward construction of pharmaceutically active six‐membered heterocycles. An emphasis is laid on the mechanistic insights to highlight the unique application of novel processes of transition‐metals in these transformations to build intricate polycyclic structures.

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Section: Introductionmentioning

confidence: 99%

Transition‐Metal Catalyzed [4+2]‐Cycloaddition Reactions: A Sexennial Update

Panda,

Mohapatra,

Ansar Ahemad

et al. 2024

ChemistrySelect

View full text Add to dashboard Cite

show abstract

“…16 Recently, we reported that [4+2] cycloadditions of β,γ-unsaturated αketo esters and internal alkynes were catalyzed by HfCl 4 . 17 Herein, we developed an enantioselective switch in asymmetric binary acid 1/In III -catalyzed conjugate alkyne addition to β,γunsaturated α-keto esters (Scheme 1).…”

mentioning

confidence: 99%

“…Subsequently, different transition metals have become prominent catalysts for conjugate alkyne addition to different unsaturated carbonyls. − In addition to terminal alkynes, the conjugate addition of alkynylsilanols to enones was also achieved by Hayashi but required harsh conditions . Recently, we reported that [4+2] cycloadditions of β,γ-unsaturated α-keto esters and internal alkynes were catalyzed by HfCl 4 . Herein, we developed an enantioselective switch in asymmetric binary acid 1 /In III -catalyzed conjugate alkyne addition to β,γ-unsaturated α-keto esters (Scheme ).…”

mentioning

confidence: 99%