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The reactivity of the C2v-symmetric pentakisadduct of C60 with azomethine ylides and conjugated dienes was studied experimentally and computationally. This derivative possesses four [6,6] double bonds, each with unique electrophilicity. The Diels-Alder reaction studied is a regiospecific, kinetically and thermodynamically guided [4 + 2] process producing [5:1]-hexaadducts with an octahedral addition pattern. The kinetically controlled Prato reaction gives a mixture of regioisomeric [5:1]-hexaadducts. The synthesis of geometrically well-defined supramolecular architectures may benefit from these new types of highly functionalized [5:1]-hexaadducts. [ABSTRACT FROM AUTHOR]

Fluorinated piperidines find wide applications, most notably in the development of novel therapies and agrochemicals. Cyclization of alkenyl N -tosylamides promoted by BF 3 -activated aryliodine(III) carboxylates is an attractive strategy to construct 3-fluoropiperidines, but it suffers from selectivity issues arising from competitive oxoaminations and the inability to easily modulate the reactions diastereoselectivity. Herein, we report an itemized optimization of the reaction conditions carried out on both cyclic and acyclic substrates and outline the origins of substrate- and reagent-based stereo-, regio-, and chemoselectivity. Extensive mechanistic studies encompassing multinuclear NMR spectroscopy, deuterium labeling, rearrangements on stereodefined substrates, and careful structural analyses (NMR and X-ray) of the reaction products are performed. This revealed the processes and interactions crucial for achieving controlled preparation of 3-fluoropiperidines using I(III) chemistry and has provided an advanced understanding of the reaction mechanism. In brief, we propose that BF 3 -coordinated I(III) reagents attack C═C to produce the corresponding iodiranium(III) ion, which then undergoes diastereodetermining 5- exo -cyclization. Transiently formed pyrrolidines with an exocyclic σ-alkyl-I(III) moiety can further undergo aziridinium ion formation or reductive ligand coupling processes, which dictate not only the final product's ring size but also the chemoselectivity. Importantly, the selectivity of the reaction depends on the nature of the ligand bound to I(III) and the presence of electrolytes such as TBABF 4 . Reported findings will facilitate the usage of ArI(III)-dicarboxylates in the reliable construction of fluorinated azaheterocycles.

The reactivity of the C 2v -symmetric pentakisadduct of C 60 with azomethine ylides and conjugated dienes was studied experimentally and computationally. This derivative possesses four [6,6] double bonds, each with unique electrophilicity. The Diels-Alder reaction studied is a regiospecific, kinetically and thermodynamically guided [4 + 2] process producing [5:1]-hexaadducts with an octahedral addition pattern. The kinetically controlled Prato reaction gives a mixture of regioisomeric [5:1]-hexaadducts. The synthesis of geometrically well-defined supramolecular architectures may benefit from these new types of highly functionalized [5:1]-hexaadducts.