Friedel–Crafts approach to the one-pot synthesis of methoxy-substituted thioxanthylium salts

Abstract

An efficient synthesis of methoxy-substituted thioxanthylium salts has been developed. The reaction of diaryl sulfides with benzoyl chlorides in the presence of TfOH smoothly proceeded to give the desired thioxanthylium salts in good yields. In their UV–vis spectra, the maximum absorption wavelengths of methoxy-functionalized thioxanthylium salts were observed at around 460 nm, which show a drastic red shift compared to the parent thioxanthylium salts. The present reaction provides a versatile access to functionalized thioxanthylium salts, and therefore it constitutes a promising tool for the synthesis of biologically and photochemically active molecules.

Redox Potential Controlled Selective Oxidation of Styrenes for Regio- and Stereoselective Crossed Intermolecular [2 + 2] Cycloaddition via Organophotoredox Catalysis

“…We have developed various types of cycloaddition reactions . More recently, we have reported the design and synthesis of thioxanthylium (TXT) organophotoredox catalysts, which have high excited state reduction potentials ( E 1/2 (C*/C •– ) = +1.76 to +1.94 V vs SCE); therefore, they can efficiently oxidize styrenes such as trans -anethole to promote a radical cation Diels–Alder reaction under irradiation with green light . Based on the aforementioned background, we assumed that the TXT photocatalyst can be applied to crossed intermolecular [2 + 2] cycloaddition reactions via selective oxidation of styrenes.…”

Thioxanthylium Cations: Highly Reversible Hydrochromic Mate‐rials with Tunable Color and Moisture Sensitivity

“…Herein, we report the unprecedented discovery of hydrochromism in thioxanthylium ( Tx + ) cations, with residual water in solvent and atmospheric moisture sufficient to cause dramatic decolorization. Tx + can be easily generated by exposing chemically‐stable thioxanthene‐9‐ol ( TxOH ) precursors to common strong organic acids such as tetrafluoroboric acid, [20] triflic acid, [21] and in this work, TFA.…”

Strongly reducing helical phenothiazines as recyclable organophotoredox catalysts

“…1; PTHS ). 9 The catalyst design is based on the following considerations: (i) in order to increase the stability of the catalyst and the reducing properties, bulky and electron-donating groups such as the t Bu group are introduced at the p -position relative to the nitrogen atom on the phenothiazine catalysts; 10 (ii) in order to absorb visible light and increase the stability of the radical intermediate, the phenothiazine catalysts are endowed with a thia-bridged helically shaped structure, which expands the π conjugation compared to 10-phenylphenothiazine ( PTH-1 ). 10…”