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

Abstract

Theu niquer eactivity ands ynthetic applications of oxime acetate derivatives with N, Oa nd S substituents at the a-position are disclosed for the first time,w hich leads to 2-substitutedf ulleropyrrolidines and mono-andd isubstituted 1-fulleropyrrolines via copper-catalyzedr edox-neutral N-heteroannulation reactions with C 60 .T his transformation is operationally simplea nd has ab road substrate scope and good functional group tolerance.T heoretical calculations at the level of B3LYP/6-31G(d) were performed to elucidate the chemoselectivity of the reaction.

Copper-Mediated Radical-Induced Ring-Opening Relay Cascade Carboannulation Reaction of [60]Fullerene with Cyclobutanone Oxime Esters: Access to [60]Fullerene-Fused Cyclopentanes

“…Based on the above results and the previous report, a plausible mechanism for the formation of 2 and 3 is proposed in Scheme . In the presence of copper salt, the iminyl radical I is initially generated via a single-electron transfer process of Cu n + to the N–O bond of oxime ester 1 with a release of Cu ( n +1)+ species. − ,− , Subsequently, radical I undergoes a β-scission of the C–C bond to produce a distal radical II . Next, the addition of radical intermediate II to C 60 gives the fullerenyl radical III , which further undergoes intramolecular cyclization to deliver the fullerenyl species IV . − Oxidation of intermediate IV by Cu ( n +1)+ species formed in situ with the N–O bond as the internal oxidant furnishes cation V . ,, Finally, the nucleophilic addition of X – from CuX 2 (X = Cl and Br) affords the target products 2 and 3 .…”

“…18 We systematically investigated the reactions of [60]fullerene with oxime acetates bearing N, O, and S substituents at the αposition, achieving the synthesis of 2-substituted fulleropyrrolidines and diverse mono-and disubstituted 1-fulleropyrrolines through CuI-and CuS-catalyzed cycloaddition reactions. 19 More recently, we also disclosed an iron(II)-catalyzed redoxneutral radical cascade reaction of [60]fullerene with γ,δunsaturated oxime esters and successfully prepared free (N−H) pyrrolidino-[2′,3′:1,2]fullerenes. 20 However, these reactions are all limited to the construction of the fullerene-fused Nheterocyclic skeleton, and the transformation for the formation of a fullerene-fused carbocycle derivative has not been reported.…”

“…Wang and coworkers reported the CuBr-catalyzed heteroannulation reaction of [60]­fullerene with ketoxime acetate access to 1-fulleropyrrolines . We systematically investigated the reactions of [60]­fullerene with oxime acetates bearing N, O, and S substituents at the α-position, achieving the synthesis of 2-substituted fulleropyrrolidines and diverse mono- and disubstituted 1-fulleropyrrolines through CuI- and CuS-catalyzed cycloaddition reactions . More recently, we also disclosed an iron­(II)-catalyzed redox-neutral radical cascade reaction of [60]­fullerene with γ,δ-unsaturated oxime esters and successfully prepared free (N–H) pyrrolidino-[2′,3′:1,2]­fullerenes .…”

“…Next, the addition of radical intermediate II to C 60 gives the fullerenyl radical III, which further undergoes intramolecular cyclization to deliver the fullerenyl species IV. 18−20 Oxidation of intermediate IV by Cu (n+1)+ species formed in situ with the N−O bond as the internal oxidant furnishes cation V 19,21,22.…”

Cu(II)/Mn(III)-Promoted Synergistic Radical N-Heteroannulation Reaction: Synthesis of [60]Fullerene-Fused Tetrahydroquinoline Derivatives

“…Fullerenes and their derivatives have attracted the interest of scientists from many disciplines owing to their unique structures and properties. , Chemical modification of fullerenes has been proven to be a promising approach for the creation of new nanocarbon-based materials by introducing different functional and structural units on the cage surface or carving carbon cage skeleton itself. Over the past few decades, many efforts have been devoted to this direction and, as a result, different synthetic methods and strategies have been established, thus leading to the formation of diverse fullerene derivatives. , Free-radical reactions are among the most powerful tools for the chemical modification of fullerenes. , Especially in recent years, transition-metal-mediated radical reactions, including Mn­(III), Cu­(I)/Cu­(II), Fe­(II)/Fe­(III), Co­(II), Ni­(II), Ag­(I), W­(VI), Ir­(III), and Pb­(IV), have received growing attention because of their remarkable advantages of high efficiency, high selectivity, and high compatibility with substrates and functional groups compared with traditional light- and thermal-induced radical processes.…”