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

Abstract

The construct of the core of pyrano[3,2-c]pyrazol-7(1H)-one derivatives is realized. The key step includes a tandem cyclization, namely, a metal-free cascade 6-π electrocyclic ring closure-Michael reaction of 2-diazo-3,5-dioxo-6-ynoates (ynones). The cascade reaction cleanly generated the desired products in excellent yields under mild conditions.

Diazocarbonyl and Related Compounds in the Synthesis of Azoles

“…A cascade electrocyclization-Michael addition process for the synthesis of pyrano[3,2- c ]pyrazol-7(1 H )-ones 211 from 2-diazo-3,5-dioxo-6-ynoates (ynones) 210 was developed by Deng and co-workers [ 112 ]. The reaction tolerates a broad range of substituents giving generally excellent yields of annulated pyrazoles.…”

Tandem Reactions of Ynones: via Conjugate Addition of Nitrogen‐, Carbon‐, Oxygen‐, Boron‐, Silicon‐, Phosphorus‐, and Sulfur‐Containing Nucleophiles

“…They also developed the synthesis of pyrano[3,2‐ c ]pyrazol‐7(1 H )‐one derivatives via a similar intermediate [Eq. (96‐2)] . The process included a Michael reaction of 2‐diazo‐3,5‐dioxo‐6‐ynoates and cyclization (Scheme ).…”

Transition Metal-Free-Catalyzed Regioselective Reversal in the Cyclization of 2-Diazo-3,5-dioxo-6-ynoates/ynones/ynamide: Synthesis of Diazo γ-Pyrones and Diazo 3(2H)-Furanones

“…虽然这种 Ag(I)催化环化是一种 实用且有效的方法, 但无过渡金属催化的区域选择性逆 转环化一直是化学工作者探索的目标(Scheme 1). 我们 最近还报道了三乙胺介入 2-重氮-3,5-二氧代-6-炔酯的 环化, 得到吡喃骈 [3,2-c]吡唑-7(1H)-酮衍生物 (Scheme 1) [9] . 此外, 在 HSbF 6 -MeOH 反应体系中, 2-重氮-3,5-二 氧代-6-炔酯转化为重氮-吡喃酮; 在 HOAc-1,2-二氯乙 烷(DCE)反应体系中, 则生成重氮 3(2H)-呋喃酮 [8] .…”