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

A two-step synthesis of phenothiazines has been developed using a dual-catalytic ortho-thioarylation reaction of anilines as the key step. Activation of N-(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 ortho-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. The dual catalytic thioarylation and copper(I)-catalysed cyclisation approach was used for the four-step synthesis of methopromazine, a neuroleptic agent with antipsychotic activity.

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. The first step involves the accelerated ortho-thioarylation of phenols using N-(2-bromophenylthio)succinimide, catalysed by the Lewis acid, iron(III) triflimide and the Lewis base, bis(4-methoxyphenyl)sulfane. In the second step, the thioarylated products were converted to a series of phenoxathiins using a copper-mediated, Ullmann-type, C-O bond forming cyclisation reaction. The synthetic utility of this two-step approach for the preparation of biologically relevant phenoxathiins was demonstrated using natural product-based phenols.

Transition-Metal-Free Synthesis of 4-Amino Isoquinolin-1(2H)-ones via Tandem Reaction of Arynes and Oxazoles

A facile and transition-metal-free method for the synthesis of 4-amino isoquinolin-1(2H)-ones has been developed. Arynes react with 4, 5-disubstituted oxazoles through a tandem Diels-Alder reaction/dehydrogenation-aromatization/tautamerization process to produce 4-amino isoquinolin-1(2H)-ones...

Acylalkylation of Arynes Generated from o-Iodoaryl Triflates with Hydrosilanes and Cesium Fluoride

An efficient method to generate aryne intermediates from o-iodoaryl triflates triggered by triethylsilane and cesium fluoride is disclosed. This method realized the acylalkylation of arynes using easily available o-iodoaryl triflate-type precursors, which was difficult when using conventional nucleophilic activators. A wide range of (hetero)arenes including various fused benzothiazoles were successfully synthesized from o-iodoaryl triflates by virtue of their good accessibility and divergent transformations of aryne intermediates.

Acid-Mediated Sulfonylthiolation of Arenes via Selective Activation of SS-Morpholino Dithiosulfonate

A trifluoroacetic-acid-mediated desulfurilative sulfonylthiolation of arenes using SS-morpholino dithiosulfonate is described. This system is based on selective activation of the morpholino group over the tosyl group of the doubly transformable sulfur surrogate. Mechanistic studies suggested that the reaction proceeds through electrophilic aromatic substitution followed by sulfur extrusion. The wide substrate scope of this reaction and the transformability of the resulting thiosulfonates enable expeditious access to divergent multifunctionalized sulfides.

One-step synthesis of benzo[b]thiophenes by aryne reaction with alkynyl sulfides

An aryne reaction with alkynyl sulfides affording benzo[b]thiophenes is disclosed. A wide range of 3-substituted benzothiophenes were synthesized from easily available o-silylaryl triflates and alkynyl sulfides in a one-step intermolecular manner. The synthesis of diverse multisubstituted benzothiophene derivatives involving a pentacyclic compound was achieved by virtue of the good functional group tolerance and versatile C2 functionalizations.

Perfluoroalkylation of Thiosulfonates: Synthesis of Perfluoroalkyl Sulfides

A practical synthesis of perfluoroalkyl sulfides is described. The method employs stable and readily accessible thiosulfonates as new electrophiles with commercial nucleophilic perfluoroalkylating reagents. The mild reaction conditions allow access to a wide variety of both aryl- and alkyl-substituted perfluoroalkyl sulfides amenable to pharmaceutical development. Furthermore, the reaction operation is straightforward, odorless, does not produce toxic wastes, and, therefore should appeal to practitioners in industrial-scale productions.