Synthesis of [60]Fullerene-Fused Spiroindanes by Palladium-Catalyzed Oxidative Annulation of [60]Fullerene with 2-Aryl Cyclic 1,3-Dicarbonyl Compounds

Abstract

A convenient and facile palladium-catalyzed reaction of [60]fullerene (C60) with 2-aryl cyclic 1,3-dicarbonyl compounds via the enolate-directed sp(2) C-H activation and sp(3) C-H functionalization has been exploited to synthesize the novel and rare C60-fused spiroindanes for the first time. This reaction is easy to perform with broad substrate scope and provides diversified products in 20-50% yields. A plausible reaction mechanism involving the palladium-catalyzed enolate-directed C-H activation and subsequent cyclization has been proposed, and the electrochemistry of the C60-fused spiroindanes has also been investigated.

Synthesis of [60]Fullerene‐Fused Allylbenzofurans via Palladium‐Catalyzed Migration Reaction†

“…[ 1 ] Over the past 30 years, functionalization of fullerenes has received special attention, and various protocols have been designed for the preparation of structurally diverse fullerene species. [ 1‐3 ] Among them, transition‐metal‐catalyzed transformations, including radical reactions, [ 2f,4 ] coupling reactions, [ 2g,5 ] C—H activation reactions, [ 2h,6 ] and asymmetric 1,3‐dipolar reactions, [ 2i,7 ] have emerged as a powerful tool to construct a variety of fullerene‐based nanostructures. These transformations typically exhibit high conversion and yield, remarkable chemo‐ and regio‐selectivity, and allow the synthesis of unique and/or sophisticated fullerene molecular architectures that are difficult or inaccessible with conventional approaches.…”

“…In this chemistry, (1) the use of 1,2‐bis(diphenylphosphino)benzene (DPPBz) as a ligand is crucial for the success of the present transformation; (2) the reaction is most likely to happen via C—O bond cleavage to form a π‐allylpalladium species followed by the allyl‐ migration and intermolecular cycloaddition sequential process; (3) the transformation shows high chemo‐ and regio‐selectivity, and is flexible with regard to allyl‐migration site, providing a new, direct and efficient approach to rare [60]fullerene‐fused benzofurans. [ 6c,9 ]…”

Transition‐Metal‐Catalyzed Synthesis of Spiro Compounds through Activation and Cleavage of C−H Bonds

“…They also evaluated the efficacy of PEPPSI‐IPr catalytic species using similar type of substrates with non‐ or weakly activated 1,3‐dienes ( 130 ) for the synthesis of spiroindanes ( 131 , Scheme 30). [48] In these reactions, PEPPSI‐IPr with Cu(OAc) 2 is likely to form a palladium diacetate complex. Wang et al ., in 2016, carried out carbopalladation of such palladacycles with C 60 under oxidative conditions to synthesize C 60 ‐fused spiroindanes ( 134 , Scheme 31).…”

“…They also evaluated the efficacy of PEPPSI-IPr catalytic species using similar type of substrates with non-or weakly activated 1,3-dienes (130) for the synthesis of spiroindanes (131, Scheme 30). [48] In these reactions, PEPPSI-IPr with Cu(OAc) 2 is likely to form a palladium Scheme 24. Oxidative spirocyclization of isoquinolones with α-diazo-1,3-indandiones.…”

“…[23] Glorius's group discovered a dearomatized spirocyclopropane intermediate in a Rh(III)-catalyzed CÀ H activation process during the synthesis of bridge polycyclic molecules via Wagner-Meerwein-type rearrangement reaction (Scheme 10). [24] They isolated various such spirocyclopropanes (49) using N-phenoxyacetamide (47) and 7-azabenzonorbornadiene (48) in the presence of [Cp*Rh(OAc) 2 .H 2 O] catalyst and DCM as solvent at room temperature. The NÀ O bond cleavage proceeds through a low energetic intramolecular nucleophilic attack in a seven memebered rhodacycle.…”