Rh-Catalyzed Annulation of Benzoic Acids, Formaldehyde, and Malonates via ortho-Hydroarylation to Indanones

Abstract

A three-component reaction from readily available low-cost materials of benzoic acids, formaldehyde, and malonates for the preparation of indanones by rhodium catalysis is reported. The annulation is initiated by an ortho-hydroarylation of benzoic acids, and a Lewis acid is not required. The solvent has a significant influence to the reaction, and 2-substituted or nonsubstituted indanones are obtained by the change of solvent.

DFT studies on rhodium(iii)-catalyzed synthesis of indanones from N-methoxybenzamides via C–H activation reaction

“…The indanone scaffold can be accessed by carbocyclization, hydroacylation, [4+1] cycloaddition, and carboxylic acid directed annulation under Rh catalysis. [28][29][30] In 2020, the Sharma group proposed a new synthesis method of the 3-trifluoromethyl indanone scaffold. Rh(III) catalyzed the reaction of N-methoxybenzamide with b-trifluoromethyl-a,b-unsaturated ketone to synthesize the 3-trifluoromethyl indanone product with the involvement of trifluoroethanol.…”

Synthesis of Cyclopentenones through Rhodium-Catalyzed C–H Annulation of Acrylic Acids with Formaldehyde and Malonates

“…We had recently shown that a three-component annulation of benzoic acids and formaldehyde as well as malonates gave indanones via aromatic C–H activation by rhodium catalysis . We questioned if a proposed key intermediate II could be formed through the rhodium activation of the vinylic C–H bond of acrylic acids (Scheme ).…”

“…16 The strategy of combining positionally selective C− H activation and multicomponent reaction would lead to We had recently shown that a three-component annulation of benzoic acids and formaldehyde as well as malonates gave indanones via aromatic C−H activation by rhodium catalysis. 17 We questioned if a proposed key intermediate II could be formed through the rhodium activation of the vinylic C−H bond of acrylic acids (Scheme 2). This was then thought to undergo an insertion into methylenemalonates, which could be formed in situ by formaldehyde and malonates under the reaction conditions, to generate intermediate IV.…”

“…The failure to produce the desired cyclopentenone product was not unexpected when the catalytic system we used previously for aryl carboxylic acids was employed (see the Supporting Information). 17 To improve the reactivity of the rhodium catalyst, a variety of additives were screened. To our delight, the desired cyclopentenone 4aa was obtained in 44% isolated yield when 20 mol % AgSbF 6 was employed (see the Supporting Information).…”

Copper/Palladium Bimetallic System for the Synthesis of Isobenzofuranones through [4 + 1] Annulation between Propiophenones and Benzoic Acids

“…Unfortunately, in the early exploration, such transformation could not be realized by using any kind of copper catalyst, so we turned to think about introducing a second catalytic system to develop a bimetallic system. In the latest years, various works involving transition-metal-catalyzed C–H activation to fulfill the intermolecular annulation were reported . Among this literature, benzoic acid and benzamide derivatives were highlighted as the most common substrates to react with different alkenes or alkynes, thus constructing corresponding benzoheterocycle products.…”