Synthesis of [60]Fullerene-Fused Tetrahydroazepinones and Azepinonimines via Cu(OAc)₂-Promoted N-Heteroannulation Reaction

Abstract

A convenient and efficient Cu(OAc)2-mediated N-heteroannulation reaction of [60]fullerene with N-sulfonylated o-amino-aromatic methyl ketones or O-alkyl oximes has been reported for the synthesis of novel and scarce [60]fullerene-fused tetrahydroazepinones and -azepinonimines in a highly selective manner. Moreover, a possible mechanism involving two pathways is proposed on the basis of the experimental observations.

Palladium-catalyzed heteroannulation of [60]fullerene with N-(2-arylethyl) sulfonamides via C–H bond activation

“…The ESI mass spectra of 2a-2i gave the correct molecular ion peaks. In their 13 C NMR spectra, the observation of at least 51 lines in the range of 133-156 ppm for the sp 2 -carbons of the C 60 skeleton, and two peaks at 78-80 ppm and 70-72 ppm for the two sp 3 -carbons of the fullerene cage, is consistent with the C 1 symmetry of their molecular structures. The IR spectra of 2a-2i showed two strong absorptions at 1330-1350 cm −1 and 1140-1160 cm −1 due to the sulfonamide group.…”

“…All products 2a-2i were unambiguously characterized using HRMS, 1 H NMR, 13 C NMR, FT-IR and UV-vis spectra. The ESI mass spectra of 2a-2i gave the correct molecular ion peaks.…”

“…9 A related study on C 60 -fused tetrahydroazepinones and -azepinonimines formed from the Cu(OAc) 2 -promoted heteroannulations of C 60 with N-sulfonylated o-amino-aromatic methyl ketones or O-alkyl oximes was recently disclosed. 13 Besides the sulfonamide group, another functional group such as ketone or oxime group was required to facilitate the radical pathway.…”

Reactivity and Synthetic Applications of α‐Functionalized Oxime Acetates: Divergent Access to Fulleropyrrolidines and Mono‐ and Disubstituted 1‐Fulleropyrrolines via Copper‐Catalyzed Redox‐Neutral N‐Heteroannulation with [60]Fullerene

“…B then undergoes rapid homolysis of the C–C bond to generate the highly active radical species C (X=N), which could attack C 60 to form fullerenyl radical D . Radical D is subsequently further oxidized by the high‐valent Cu generated in situ to provide biradical intermediate E . Next, intramolecular cyclization occurs to afford 2‐substituted fulleropyrrolidine 2 via the biradical C–C coupling.…”

Addition reaction of alkyl radical to C60 fullerene: Density functional theory study

“…For example, methanofullerene ( [6,6]-phenyl-C 61 -butyric acid methyl ester: PCBM) is one of the most useful n-type organic semiconductors [1][2][3][4][5][6][7]. The interaction between organic radical and fullerene has recently attracted considerable interest because the electronic properties of carbon materials are drastically changed by the addition of radical [8][9][10][11][12][13][14][15].…”