Synthesis of Fused Dihydroazepine Derivatives of Fullerenes by a Rh‐Catalyzed Cascade Process

Abstract

A synthetic methodology is reported that functionalizes C60 and C70 fullerenes with dihydroazepine rings by a cascade reaction encompassing a rhodium‐catalyzed cycloisomerization of 1,5‐bisallenes and a [4+2] cycloaddition. This transition metal‐catalyzed cascade reaction provides a versatile and step‐economical approach to the synthesis of 6,7‐membered polyheterocyclic fullerene adducts. Electrochemical characterization of the products obtained ventures their application in organic and perovskite photovoltaic devices.

A Rh(I)‐Catalyzed Cascade Cyclization of 1,5‐Bisallenes and Alkynes for the Formation of cis‐3,4‐Arylvinyl Pyrrolidines and Cyclopentanes

“…In this study, the oxidative coupling between the allene moiety and the alkyne is preferred over the alkyne-alkyne coupling (TS(A2 A3), ΔG � = 19.0 kcal • mol À 1 ). [35][36][37][38] The coordination of DMAD to A3 gives A4, a 16electron square-pyramidal complex. The subsequent C�C insertion (Schore mechanism [48] ) is preferred to occur in the equatorial RhÀ C bond (TS 1 (A4 A5)) to produce the conjugated rhodacycloheptadiene A5.…”

“…Our group recently developed a cascade reaction involving 1,5-bisallenes and alkenes, [35] including C 60 , [36] to obtain fused 6,7-membered rings (Scheme 1d). The mechanism is postulated to proceed via an initial rhodium-catalysed cycloisomerization of the bisallene leading to a non-isolable 1,2-dimethylenecycloheptene scaffold, followed by a regioselective Diels-Alder reaction with alkenes in which the rhodium does not participate.…”

“…Furthermore, in rhodium-catalyzed cycloaddition reactions it is known that alkynes are much more reactive than alkenes, and that the reactivity of allenes falls somewhere between the two. [37][38][39] Thus, as a continuation of our programme based on the development of rhodium-catalysed cycloadditions involving allenes, [35][36][37][38][40][41][42] we asked ourselves what the favoured reaction pathway would be if we treated 1,5-bisallenes with alkynes under rhodium catalysis. We reasoned that the greater reactivity of alkynes as compared to alkenes might favour a fully rhodium catalysed cascade process.…”

Rh(I) Complexes with Hemilabile Thioether-Functionalized NHC Ligands as Catalysts for [2 + 2 + 2] Cycloaddition of 1,5-Bisallenes and Alkynes

“…Instead, very interesting reactivities were observed (Scheme ). In the reaction of 1,5-bisallenes with alkenes, dihydroazepine- and dihydrooxepine-fused ring systems were obtained in good yields . Further mechanistic study by DFT calculations showed that the reaction took place through a rhodium-catalyzed cycloisomerization/Diels–Alder cascade encompassing oxidative coupling of the rhodium to the central carbon atoms of both allenes (intermediate I ) followed by a β-hydride elimination (intermediate II ) and reductive elimination of the rhodium to afford a non-isolable cycloheptatriene derivative III , which gave a further Diels–Alder reaction with the alkene (Scheme a).…”

Isocyanide-Induced Annulation Leading to Cyclopento-, Methano-, and Cyclopentano-[60]Fullerene Derivatives

“…Fullerenes are promising building blocks in biomedicine, organic and perovskite solar cells, (photo)­electrocatalytic systems, and simple structural scaffolds for functional materials due to their physicochemical, electrochemical, and photophysical properties and structural characteristics. Regioselective functionalization reactions of fullerenes have been actively sought after to improve the synthetic yield and the structural diversity of fullerene derivatives to realize their potential …”