Synthesis of acyloxyl pyrazolines by copper-mediated aminoacyloxylation of unsaturated ketohydrazones

Abstract

An efficient and step-economical copper-mediated intra-/intermolecular aminoacyloxylation of β,γ-unsaturated hydrazones has been developed. Copper carboxylates serve as both reaction promoters and carboxylate sources in these easily conducted reactions. This method provides straightforward access to diversely useful acyloxyl pyrazolines, which are hard to access traditionally, in good to excellent yields.

Radical Cascade Reactions of β,γ‐Unsaturated Hydrazones/Oximes

“…In 2018, Li's group developed a copper‐mediated intra‐/intermolecular alkene aminoacyloxylation reaction (Scheme 26). [40] This strategy could efficiently provide a variety of acyloxyl‐functionalized pyrazolines, which are valuable building blocks in medicine and materials science. A possible mechanism was depicted in Scheme 26.…”

Update on the Synthesis of N‐Heterocycles via Cyclization of Hydrazones (2017–2021)

“…[19] Copper-catalyzed intramolecular cyclization of hydrazones with unsaturated bonds has recently been developed widely into one of the most reliable methods of synthesizing nitrogencontaining heterocyclic compounds. [20][21][22] Zora's group first reported using the coppermediated electrophilic cyclization of α,β-alkynic hy-drazones 3 to synthesize a series of pyrazoles 4 (Scheme 1) early in 2011. [23] In this study, α,β-alkynic hydrazone derivatives 3 were prepared efficiently in moderate to excellent yields at 80 °C via condensation of hydrazines 2 with acetylenic aldehydes and ketones 1.…”

Mn- and Co-Catalyzed Aminocyclizations of Unsaturated Hydrazones Providing a Broad Range of Functionalized Pyrazolines

“…There have also been reports on the use of acridinium 28 and ruthenium 29 photocatalysis to furnish pyrazolines, such as III and V . 30 − 37 Collectively, these approaches demonstrate the general interest in methods for the preparation of functionalized pyrazolines. However, convenient access is desirable not only to alcohols but also to an expanded set of products that include other groups.…”

“…However, this process affords a mixture of aldehydes II (20%), alcohols III (18%), and hydroperoxides IV (40%), thus requiring a subsequent reductive step to convert the mixture into alcohol products. There have also been reports on the use of acridinium and ruthenium photocatalysis to furnish pyrazolines, such as III and V . − Collectively, these approaches demonstrate the general interest in methods for the preparation of functionalized pyrazolines. However, convenient access is desirable not only to alcohols but also to an expanded set of products that include other groups.…”