Cp*Co^III-Catalyzed C(7)–H Bond Annulation of Indolines with Alkynes

Abstract

An efficient protocol for the synthesis of biologically essential pyrroloquinolinones has been developed under Cp*CoIII catalysis, which involves a cascade reaction of C(7)–H alkenylation with alkynes followed by nucleophilic addition. A wide variety of internal alkynes including enyne, diyne, and ynamide and more challenging terminal alkynes were successfully employed for the annulation in good to excellent yield with high regioselectivity.

Rhodium(III)-Catalyzed Redox-Neutral [4 + 1]-Annulation of Unactivated Alkenes with Sulfoxonium Ylides

“…The transition-metal-mediated C–H activation followed by the annulation with π-components is a powerful method to construct various heterocycles or carbocycles. Mainly, this transformation has been accomplished with π-systems such as alkynes, dienes, bis -alkynes, benzynes, and activated alkenes . Due to the prevalence of unactivated alkenes in several bioactive natural products and pharmaceuticals, expanding this annulation reaction with electronically unbiased unactivated alkenes will be interesting for the synthesis of carbocyclic systems.…”

“…Among the various reports on annulation reactions, [4 + 1] cyclization with unactivated alkenes is not reported in the literature. Instead, this interesting yet rare cyclization is limited only to reactive and electronically biased systems such as activated alkenes, diazo compounds, etc. , …”

“…With the continuous interest of our group in exploring the reactivity of unactivated alkenes and redox-neutral reactions, ,, we thought to develop a methodology for [4 + 1] cyclization of unactivated alkenes with sulfoxonium ylide using a Rh­(III) catalyst (Figure c). To our delight, we have successfully developed a methodology for [4 + 1] annulation of the unactivated alkenes using sulfoxonium ylide as a directing group resulting in indanone motifs (Figure d).…”

Data-Driven Analysis of Reactions Catalyzed by [CoCp*(CO)I2]

“…Numerous interesting examples of the use of [Cp*Co­(CO)­I 2 ] were reported in terminal couplings and heterocycle formation. − For bond activations through novel synthetic routes, discovering more efficient and profitable methods of using the various resources, reducing costs, and promoting the use of [Cp*Co­(CO)­I 2 ] is highly desirable. Although several mechanistic and computational studies have been carried out, − the appropriate choice of various solvents and additives, the reaction time, and the temperature remain very important.…”

“…With regard to [Cp*Co­(CO)­I 2 ]-mediated C–H activation, various functional groups, including amides, nitrogen-containing heterocycles, and carboxylic acids, are employed as directing groups (DGs) in catalytic C–H bond functionalization. , Thus, investigating different DGs in combination with other reaction parameters and their effects on the yields of the studied catalytic reactions is of considerable interest.…”