Transition-Metal-Free HFIP-Mediated Organo Chalcogenylation of Arenes/Indoles with Thio-/Selenocyanates

Abstract

We have developed a protocol for the synthesis of diaryl thio-/selenoethers by the reaction of aryl chalcogenocyanates with electron rich arenes/hetero arenes via HFIP promoted C–H activation. The reaction produces chalcogenides in good to excellent yields under mild conditions without the need of a transition metal as a catalyst. The HFIP-mediated reactions tolerated a wide range of functional groups and set the stage for the synthesis of diversely decorated chalcogenides. A mechanism involving activation of the C–H bond through hydrogen bonding is proposed.

Metal-free and Atom-efficient Protocol for Diarylation of Selenocyanate by Diaryliodonium Salts

“…These transformations have been previously observed on the arylselenation of electron-rich arenes. 32 Footnote: a Reaction conditions: phenyl(2,4,6-trimethoxyphenyl)iodonium trifluoroacetate 1a (5 mmol), KSeCN (5.5 mmol), EtOAc (20 mL); b phenylselenocyanate (1 mmol), TMP-I (1.1 equiv. ), HFIP (2 mL), inert conditions; c Isolated yield.…”

“…), HFIP (2 mL), inert conditions; c Isolated yield. Initially, for the diarylation we employed the previously reported conditions 32 which include PhSeCN and TMP-I as the reactants and HFIP as a solvent. However, under these conditions the yield of the target product was only 15% (Figure 2-B; for details see the Supporting Information, Table S1) and therefore we focused on optimization of the diarylation and conductance of this reaction without isolation of intermediate products.…”

“…The chemistry of ArSeCN, however, provides an exciting option which helps to increase AE. Withal, Goswami and coworkers 32 reported the arylation of ArSeCN by electron-rich arenes via electrophilic activation of the SeCN moiety by hydrogen bond donating hexafluoroisopropanol (HFIP). We assumed that their approach, including the choice of reactants and the solvent, can be extended to unsymmetrical diaryliodonium salts bearing an electron-rich auxiliary group.…”

Nucleophilic Selenocyanation from Selenium Dioxide and Malononitrile

“…7 They have potential for use as intermediates for the construction of selenium-containing heterocycles like selenazoles, 8 selenophenes, 9 or ebselen derivatives, 10 as well as a new source of cyanating reagent. 11 Thus, there is clear interest in new approaches involving the SeCN group.…”

Site-selective C5–H andN–H alkylation of unprotected 8-aminoquinolines

“…To gain more insight about the reaction mechanism, some experiments were performed and the results are outlined in Scheme S1, ESI †. Based on the reaction results and on the basis of former literature, 29–34 we propose a plausible mechanism for the synthesis of C5- and N -alkylated 8-aminoquinolines. It has been suggested that the 1,6-conjugated addition to the p -QM occurs from the C5 position because this amine group of 8-aminoquinoline is blocked for nucleophilic attacks due to the strong hydrogen bonds between the amine group of 8-aminoquinoline and HFIP (Scheme S2 and Fig.…”