Synthesis of Polycyclic Aromatic Hydrocarbons Decorated by Fluorinated Carbon Acids/Carbanions

Development of Stable Carbanionic Substituents

During the past decade, carbon (C-H) acids depicted as 'Tf2 CHR' (Tf=CF3 SO2 ) have attracted considerable attention as a new class of superacidic molecules, which show stronger acidity than sulfuric acid molecules. In recent years, the author has developed a synthetic methodology for such strong acids and has opened the door to chemistry of highly stabilised carbanions [Tf2 CR]- , which are the conjugate bases of the carbon acids. These carbanion-containing salts are stable and easy-to-handle species. Our efforts have revealed that the ionic but lipophilic characters of this type of carbanion can be used as a unique 'substituent' for increasing both the water solubility and the lipophilicity of organic compounds. This Personal Account provides an overview of our [Tf2 CR]- chemistry, including its synthesis, structure, reactivity, and applications.

Dodging the Conventional Reactivity of o-Alkynylanilines under Gold Catalysis for Distal 7-endo-dig Cyclization

A direct ring-closing strategy involving a less facile 7-endo-dig carbacyclization of o-alkynylaniline derivatives for the synthesis of benzo[b]azepines has been presented. The trivial well-documented 5-endo-dig cyclization in o-alkynylaniline derivatives due to high nucleophilicity of nitrogen has been overcome by using their vinylogous amides under gold catalysis to access a wide array of benzo[b]azepines in an atom economical way with excellent functional group compatibility. Deuterium scrambling experiments and DFT studies favor a mechanism involving stabilizing conformational change of the initially formed seven-membered vinyl gold intermediate through a key cyclopropyl gold carbene intermediate and its subsequent protodeauration mediated by the counter anion.

Iron-Catalyzed Synthesis of 13-Aryl-13H-indeno[1,2-l]phenanthrene via Double Annulations of 2-Alkynyl Biaryls

An Fe(III)-catalyzed expedient synthesis of 13-aryl-13H-indeno[1,2-l]phenanthrene is described by a double annulations of 2-alkynyl biaryls, initiated by the activation of acetal. This strategy provides a simple, efficient and regioselective synthesis of varieties of indenophenanthrene derivatives from easily available starting materials under mild conditions in high to excellent yields. A plausible reaction mechanism is proposed.

TfOH-promoted synthesis of indoles and benzofurans involving cyclative transposition of vinyl ketone

A metal-free approach to construct indole ring from vinylogous amides derived from o-alkynylanilines involving cyclization, retro-aza-Michael and amine trapping cascade is reported here. This atom-economical transformation has been extended to...