Concise preparations of elaborated polycyclic and heterocyclic systems present in natural products were obtained using the nosyl group as a functional protecting group not only to mask the reactivity of a sensitive moiety but also to provide a structure desired in the final target. The group is transferred to the substrate during deprotection through a novel extension of the Truce-Smiles rearrangement in tandem with a 1,4-addition. This strategy provides access to a ring system laden with valuable functionalities for subsequent manipulations and can serve as a versatile building block for the construction of more complex molecular architectures such as indoles in a manner compatible with the concepts of green chemistry and atom economy.
Substituted anilines containing a sulfonyl group may be oxidized in situ in the presence of methanol and a hypervalent iodine reagent to form an active iminium species. Subsequent addition of phosphines or phosphites in the same pot produces meta-substituted anilines in good yields. This formal C-H bond functionalization is a direct and efficient means of selectively substituting the meta-position of anilines to produce aromatic phosphonium ions or phosphonates.
A new stereoselective arylative cyclopropanation process involving treatment of halogenated dienone systems in the presence of a Michael donor containing a nitro-aryl-sulfone has been developed. This transformation enables production of an arylated cyclopropane under mild conditions and occurs via a Michael-Smiles ring closure cascade process, reflecting the concepts of green chemistry and atom economy.
An arylative aziridination process has been developed from dibrominated phenols containing a Fukuyama sulfonamide on the lateral chain. A two-step procedure involving the formation of a dienone by a phenol oxidation reaction mediated by a hypervalent iodine reagent (Kita reaction) followed by an intramolecular arylative aziridination process was used. This second step occurred under mild conditions via a Michael-Smiles ring-closure cascade, producing sulfur dioxide as the only byproduct. Additionally, a stereoselective approach was observed with tyrosine derivatives. This transformation respects the rules of green chemistry and atom economy. These new polyfunctionalized scaffolds could offer several synthetic possibilities for the total synthesis of natural products such as the main core of Aspidosperma alkaloids.Aziridines 1a-f are small heterocycles that can be used to produce a variety of more complex structures, including natural products. With epoxides 1g and cyclopropanes, 1h they represent the most important three-membered ring systems. 1 Therefore, they have attracted the attention of the synthetic community and several processes have been described in the literature. Currently, the consensus is that sustainable, environmentally benign routes to desirable synthetic targets should be atom economical and free of protecting groups 2 to respect the concept of "green chemistry." With this idea in mind, we were recently interested in the development of new processes enabling the rapid formation of functionalized heterocycles promoted by a Michael-Smiles tandem process 3 as well as their extension to halogen-dienone systems to yield cyclopropanes. 4 Encouraged by these results, we decided to extend this approach to a nitrogen nucleophile to yield aziridines. These heterocycles were produced from reactive dienones that were readily
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