Rhodium‐Catalyzed C−H Activation/Annulation of N‐Aryl‐pyrazolidinones with Vinylene Carbonate

Abstract

A rhodium‐catalyzed C−H activation/annulation of N‐aryl‐pyrazolidinones with vinylene carbonate was developed. The utilization of vinylene carbonate as the acetylene surrogate furnished the successful construction of non‐substituted 5,6‐pyrazolo[1,2‐a]cinnoline derivatives, which are difficult to synthesize through other procedures. In this work, a series of variously substituted pyrazolo[1,2‐a]cinnolines were obtained in yields up to 98 % with broad substrate scope and excellent selectivity. Moreover, external oxidants were not required in this protocol with H2O and CO2 as the clean by‐products.

Synthesis of Fluoren‐9‐ones via Pd‐Catalyzed Annulation of 2‐Iodobiphenyls with Vinylene Carbonate

“…Soon afterwards, Miura, Zhang, Li, and Ma group et al [8–9] . successfully synthesized a variety of heterocycles via high‐valent Rh(III), [8,9d–j] Co(III), [9a] Mn(I), [9b] and Ru(II) [9c] catalysis. In addition, vinylene carbonate could also serve as the alkenyl ether synthon in transition‐metal‐catalyzed C−H bond activation reactions.…”

Advancement of vinylene carbonate as a coupling partner in metal-catalyzed C–H functionalization

“…These serial transformations obviously showcase the synthetic potential of this methodology involving VC (Scheme 12). [54][55][56] Continuously researching powerful synthetic tactics towards isoquinolino [1,2-b]quinazolinones is attractive due to their privileged biological activities. On the basis of the theme of C-H [4 + 2] annulation reactions of 2-arylquinazolinones with alkenes, alkynes, benzyne, aryl halides, and so forth, several research groups independently employed VC as a treating partner to participate in the cyclization reaction of 2-arylquinazolinones 40 (Scheme 13).…”

“…These serial transformations obviously showcase the synthetic potential of this methodology involving VC (Scheme 12). 54–56…”

Construction of Vinyl‐SubstitutedN‐HeterocyclesviaRh(III)‐Catalyzed C−H Functionalization/Annulation of Pyrazolidinones

“…[8,9] However, most of the coupling partners are only suitable for 1,2-disubstituted acetylenes; this results in the products being composed of 1,2-disubstituted carbon-carbon double bonds. [10] Therefore, it is a crucial task to construct non-or mono-substituted heterocycles. Considering the convenience of synthesis, utilizing acetylene equivalents is a wise choice.…”