Synthesis of Thiazoloindole α-Amino Acids: Chromophores Amenable to One- and Two-Photon Induced Fluorescence.

Thiazoloindole α-amino acids have been synthesized in four steps from tryptophan using a dual-catalytic thiolation reaction and a copper-mediated intramolecular N-arylation process. Late-stage diversification of the thiazoloindole core with electron-deficient aryl substituents produced chromophores that on one-photon excitation displayed blue-green emission, mega-Stokes shifts, and high quantum yields. The thiazoloindole amino acids could also be excited via two-photon absorption in the near-infrared, demonstrating their potential for biomedical imaging applications.

Thioarylation of anilines using dual catalysis: two-step synthesis of phenothiazines.

A two-step synthesis of phenothiazines has been developed using a dual-catalytic -thioarylation reaction of anilines as the key step. Activation of -(2-bromophenylthio)succinimide was achieved using the super Lewis acid, iron(III) triflimide and the Lewis base, diphenyl selenide, resulting in an accelerated and efficient -thioarylation reaction of various protected aniline derivatives and less reactive, unprotected analogues. The thioarylated adducts were then cyclised to the desired phenothiazines using either an Ullmann-Goldberg or Buchwald-Hartwig coupling reaction.

Synthesis of phenoxathiins using an iron-catalysed C-H thioarylation.

Phenoxathiins are an important class of sulfur-containing heterocycle, found as the core component in numerous pharmaceutically active agents and materials. Despite this importance, there are relatively few methods for the synthesis of these heterocycles that avoid complex starting materials, harsh conditions or precious transition metals. We report a two-step synthesis of phenoxathiins from phenols using iron and copper-mediated reactions.

Regioselective C-H Thioarylation of Electron-Rich Arenes by Iron(III) Triflimide Catalysis.

A mild and regioselective method for the preparation of unsymmetrical biaryl sulfides using iron(III) catalysis is described. Activation of -(arylthio)succinimides using the powerful Lewis acid iron(III) triflimide allowed the efficient thiolation of a range of arenes, including anisoles, phenols, acetanilides, and -heterocycles. The method was applicable for the late-stage thiolation of tyrosine and tryptophan derivatives and was used as the key step for the synthesis of pharmaceutically relevant biaryl sulfur-containing compounds such as the antibiotic dapsone and the antidepressant vortioxetine.