Solvent-free synthesis of benzothiazole-based quaternary ammonium salts: precursors to ionic liquids

Abstract

This paper is dedicated to Professor Richard A. Bartsch on the occasion of his 70thbirthday and retirement Abstract A series of 13 benzothiazolium iodide salts have been prepared in solvent-free conditions by optimizing the reaction. An additional 26 benzothiazolium salts with bistrifluoromethanesulfonimide and trifluoromethylsulfonate were prepared via simple metathesis reactions from the iodide precursors. Out of a total of 39 prepared salts, 26 were identified as ionic liquids, with melting points as low as 42 o C observed for dodecylbenzothiazolium bistrifluoromethanesulfonimide. All prepared compounds have been characterized using FTIR, 1 H, 13 C NMR, and HRMS analyses. The thermal stabilities as well as melting points of these salts were also analyzed.

A simple route to phosphamethine cyanines from S,N-heterocyclic carbenes

“…The systematic synthesis of N-alkylbenzothiazolium iodides through the treatment of benzothiazole with alkyl iodides was described by Nigrey and Garito, 17 and more recently this has been expanded upon by Rogers and co-workers. 18 Thus, spectroscopic data for a large library of these has been compiled but crystallographic data for many of these reported compounds were never reported. During the course of our investigations, we were able to obtain crystal structures for several of these known compounds.…”

“…For completeness, we have included full characterization data for all of the dimethylbackbone derivatives we prepared (Scheme 1). All of these salts were synthesized in the same solvent-free conditions as described by Rogers et al for the benzannulated analogues, 18 and their 1 H and 13 C NMR data show similar features, namely, the very large deshielding of the C1 carbon (ca. 145 ppm) and its bound proton (ca.…”

“…All chemicals and reagents were purchased from Sigma-Aldrich and used without further purification. Deuterated solvents were dried according to literature procedure when necessary, and all other solvents were dried over 18 were synthesized according to literature procedures. NMR spectra were recorded at room temperature on a Bruker Avance III 500 MHz, Bruker Avance Ultrashield 300 MHz or Bruker Avance DPX 300 MHz spectrometers.…”

“…Spectroscopic data are consistent with previous reports. 24,25 General synthesis of N-alkyl-4,5-dimethyl thiazolium iodides Thiazolium iodide salts were synthesized using a variation of a method reported by Rogers et al 18 4,5-dimethyl thiazole and a small excess of the given alkyl iodide were stirred and heated to 70 °C under nitrogen until most or all of the liquid mixture had been replaced by a white to off-white solid (1 to 4 days, depending on the alkyl iodide). Once cooled to room temperature, this solid was triturated and washed with toluene, then dried under vacuum, affording the analytically pure N-alkyl-4,5-dimethyl thiazolium iodide salt as an off-white to white solid.…”

Base induced synthesis of 4H-1,4-benzothiazines and their computational studies

“…The solid thus obtained was washed with diethyl ether to remove unreacted material (yield: 95%). 24 Fig. 4 UV-vis absorption spectra of compounds 3(c), 3(d), 3(g) and 3(i) in chloroform.…”