ALIPHATIC THIOETHERS BY S-ALKYLATION OF THIOLS VIA TRIALKYL BORATES

Abstract

A simple and convenient one-pot procedure is described for the synthesis of thioethers via boron esters. This procedure involves in-situ generation of alkyl sulfates by reaction of trialkyl borates with concentrated sulfuric acid and subsequent reaction with thiols in the presence of pyridine. The reactions with boron esters of primary or secondary alcohols proceed cleanly at 100°C and afford aliphatic thioethers in reasonable yields (59–93%) within 24 h. Interestingly, the ¹H NMR spectra of the products showed no sign of positional isomerisms. The method fails however with thiophenol and does not yield aromatic thioethers, due to electrophilic substitution at the phenyl ring.

Keywords:

• Alkyl sulfates
• thioethers
• trialkyl borates

Acknowledgments

The Boron Research Institute of the Turkish Government is acknowledged for the financial support (BOREN-2006-12-C11>> 17).

Notes

^a Conversion yields assigned by ¹H NMR spectroscopy of the reaction mixture.

^b Isolated yield 64.2%.

^c Isolated yield 67.2%.