1,3-Dipolar Cycloaddition of Ethyl Diazoacetate to Alkynes in the Pores of Zeolite NaY

Abstract

Zeolite NaY promotes 1,3-dipolar cycloaddition of ethyl diazoacetate to alkynes having an electron-withdrawing group to afford the corresponding functionalized pyrazoles in high yields. The activation of the dipolarophile inside the pores of NaY is proposed based on the 13C MAS NMR analysis.

Diazo compounds as highly tunable reactants in 1,3-dipolar cycloaddition reactions with cycloalkynes

“…37 involve either highly reactive diazoalkanes generated in situ, 41,42 or highly stabilized diazo compounds 43 requiring elevated reaction temperatures 44 or toxic metal catalysts to attain useful reaction rates. [45][46][47][48][49][50] Now that a wide variety of diazo compounds are readily accessible from azides in a single step, we sought to assess their reactivity in strain-promoted cycloaddition reactions with forefront cycloalkynes.…”

Synthesis of Pyrano[3,2-c]pyrazol-7(1H)-one Derivatives by Tandem Cyclization of 2-Diazo-3,5-dioxo-6-ynoates (Ynones)

“…γ-Pyranone ring is often constructed by the intermolecular Michael addition of an enolate oxygen anion with conjugate ynones (an annulation reaction), as documented in the literature . Additionally, the [3 + 2] cycloaddition of diazo compounds with carbon–carbon triple bonds has been widely applied to construct pyrazole rings; however, the corresponding electrocyclizations toward these heterocycles are rarely utilized . The combination of the electrocyclization toward pyrazole synthesis and the annulation for γ-pyranone synthesis is not only interesting but also challenging.…”

Synthesis of pyrazoles through catalyst-free cycloaddition of diazo compounds to alkynes

“…13 In 2004, Li realised a breakthrough by reporting the first intermolecular cycloaddition of various adiazocarbonyl molecules to electron-poor alkynes catalysed by indium(III) chloride in water. 14 More recently, Ready extended the scope of the reaction to a wide range of alkynes by using copper acetylides in THF, 15 while other developments involved zeolite NaY as promoter in CH 2 Cl 2 , 16 and microwave-assisted reaction with the alkyne as solvent. 17 During our research, we now found that the 1,3-dipolar cycloaddition of diazo compounds to alkynes did not need any special promoter or medium, and could be simply conducted under thermal conditions with various partners.…”