Access to Optically Pure Benzosultams by Superelectrophilic Activation

Accumulation, Characterization and Reactivity of Chiral Ammonium-Carboxonium Dications in Superacid

The accumulation of chiral ammonium-oxocarbenium dications in superacid is evidenced by low-temperature NMR spectroscopy, X-ray diffraction analysis and confirmed by DFT calculations. Its potential for the diastereoselective remote hydrofunctionalization of non-activated alkene is also explored.

Exploring Superacid-Promoted Skeletal Reorganization of Aliphatic Nitrogen-Containing Compounds

Here we report a method to reorganize the core structure of aliphatic unsaturated nitrogen-containing substrates exploiting polyprotonation in superacid solutions. The superelectrophilic activation of N-isopropyl systems allows for the selective formal Csp3 -H activation/cyclization or homologation / functionalization of nitrogen-containing substrates. This study also reveals that this skeletal reorganization can be controlled through protonation interplay. The mechanism of this process involves an original sequence of C-N bond cleavage, isopropyl cation generation and subsequent C-N bond and C-C bond formation. This was demonstrated through in situ NMR analysis and labelling experiments, also confirmed by DFT calculations.

Pd-catalysed intramolecular transformations of indolylbenzenesulfonamides: ortho-sulfonamido-bi(hetero)aryls via C2-arylation and polycyclic sultams via C3 arylation

Indolyl substituted iodo-sulfonamides deliver 2-aryl(sulfonamido)indoles in the presence of Pd(OAc)2/Ph3P/Et3N; the same reactants, using Pd(OAc)2/Ph3P/K2CO3, afford indole-fused sultams.

Structurally Diverse Synthesis of Five-, Six-, and Seven-Membered Benzosultams through Electrochemical Cyclization

We have developed a metal- and oxidant-free approach to structurally diverse synthesis of benzosultams from aryl sulfonamides through an electrochemical cyclization. Upon variation of the ortho substituent on aryl sulfonamides, five-, six-, and seven-membered benzosultams were efficiently assembled in an atom- and resource-economic manner. The generality of the process is demonstrated by the formation of five- to seven-membered cyclic products from 42 substrates bearing substituents with different electronic effects and steric hindrance.

Complementary Site-Selective Sulfonylation of Aromatic Amines by Superacid Activation

Under superacidic conditions, aniline and indole derivatives are sulfonylated at low temperature with easy-to-access arenesulfonic acids or arenesulfonyl hydrazides. By modification of the functional-group directing effect through protonation, this method allows nonclassical site functionalization by overcoming the innate regioselectivity of electrophilic aromatic substitution. This superacid-mediated sulfonylation of arenes is complementary to existing methods and can be applied, through protection by protonation, to the late-stage site-selective functionalization of natural alkaloids and active pharmaceutical ingredients.