Expeditious Preparation of Open‐Cage Fullerenes by Rhodium(I)‐Catalyzed [2+2+2] Cycloaddition of Diynes and C₆₀: An Experimental and Theoretical Study

Abstract

A novel methodology to transform C into a variety of open-cage fullerene derivatives by employing rhodium(I) catalysis has been developed. This transformation encompasses a partially intermolecular [2+2+2] cycloaddition reaction between diynes 1 and C to deliver a cyclohexadiene-fused fullerene, which concomitantly undergoes a formal [4+4]/retro-[2+2+2] rearrangement to deliver open-cage fullerenes 2. Most notably, this process occurs without the need of photoexcitation. The complete mechanism of this transformation has been rationalized by DFT calculations, which indicate that, after [2+2+2] cycloaddition, the cyclohexadiene-fused intermediate evolves into the final product through a Rh-catalyzed di-π-methane rearrangement followed by a retro-[2+2+2] cycloaddition. The obtained open-cage fullerenes can be derivatized by Suzuki-Miyaura cross-coupling or subjected to ring expansion to deliver a 12-membered ring orifice in the fullerene structure. Overall, the methodology presented constitutes a straightforward entry to functional open-cage C fullerene derivatives by employing catalytic methods.

Enhanced Open-Circuit Voltage in Perovskite Solar Cells with Open-Cage [60]Fullerene Derivatives as Electron-Transporting Materials

“…The open-cage derivatives used in this study, 2a – c , were prepared by the photochemical oxidation of bis(fulleroids) 1a – c , which can be obtained from [60]fullerene in one step using our Rh(I)-catalyzed cycloaddition protocol (Scheme 1) [41]. Importantly, unlike precursors 1a - c , open-cage derivatives 2a – c do not suffer further degradation upon exposure to light and air.…”

“…However, their use as ETLs in PSCs remains unexplored. Some of us recently reported a straightforward methodology for the synthesis of open-cage fullerene derivatives (Scheme 1) [41,42]. The promising electrochemical properties and remarkable stability of these compounds, together with the fact that fullerene derivatives are so far the materials of choice as the ETL for p-i-n PSCs, prompted us to study the use of these compounds for PSCs.…”

Mechanistic Studies of Transition-Metal-Catalyzed [2 + 2 + 2] Cycloaddition Reactions

“…We were able to show that the reaction, when catalyzed by [Rh(cod) 2 ]BF 4 and Tol-BINAP, not only worked with great efficiency but also allowed for the s121 direct preparation of open-cage fullerenes 323 (Scheme 121). 322 We completed our experimental work by performing a computational study with the M06-L-D3/cc-pVTZ-PP// B3LYP-D3/cc-pVDZ-PP method of the reaction mechanism of the intermolecular [2 + 2 + 2] cycloaddition of the 1,6-diyne of Scheme 121 and C 60 catalyzed by [RhBINAP] + . To reduce the computational cost, the tosyl group of the 1,6-diyne was substituted by a mesyl group and, in the catalyst ligand, the tolyl groups were replaced by methyl groups and the binaphthyl was Rothwell et al 325,326 reported the selective synthesis of 1,3cyclohexadiene scaffolds by reaction of two alkynes and one olefin under catalysis by titanacyclopentadiene (162c) or s124 titanacyclopentane (329) aryloxide complexes (Scheme 124).…”

Decomposition of the electronic activity in competing [5,6] and [6,6] cycloaddition reactions between C60 and cyclopentadiene

“…As a result, it undergoes a variety of chemical organic reactions, the most important being the nucleophilic additions [4][5][6]. Moreover, C 60 reacts through many metal-catalysed processes like the Pauson-Khand reactions [7][8][9], the Suzuki-Miyaura reactions [10][11][12][13] or the [2 + 2 + 2] cycloadditions [14][15][16], among others. However, one of the most employed reactions for the functionalization of fullerenes and their derivatives is the Diels-Alder (DA) cycloaddition [17][18][19][20][21][22].…”