Phosphorus Pentasulfide Mediated Conversion of Primary Carbamates into Thiols

Abstract

In this paper, we report a method for the conversion of primary carbamates into thiols in the presence of phosphorus pentasulfide (P₂S₅) in refluxing toluene. Presently, no method exists in the literature for conversion of carbamates into thiols and, to the best of our knowledge, it is the first report for this type of conversion. This method presents an indirect route for the conversion of alcohols into thiols via their carbamate derivatives that may be useful in the total synthesis of compounds containing a thiol functionality.

Key words

carbamate - phosphorus pentasulfide - thiocarbamate - dithiocarbamate - thiol

• References and Notes

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• 12 Conversion of Carbamate into Thiol – Typical Procedure In a three-neck round-bottom flask, to a solution of carbamate (10 mmol) in toluene (25 mL), P₂S₅ (3.33 g, 15 mmol) was added, and the resulting suspension was heated to reflux until complete consumption of the starting material (TLC). After the reaction was complete, the reaction mixture was quenched by careful addition of water (10 mL), extracted with EtOAc (3 × 10 mL). The organic phase was dried over Na₂SO₄, filtered, and evaporated under reduced pressure to obtain the crude product that was purified by flash chromatography (hexane–EtOAc) to give the pure thiol. 3-Phenoxybenzyl Thiol Oil, yield 74%. ¹H NMR (400 MHz, CDCl₃): δ = 7.24–7.34 (m, 3 H), 6.87–7.10 (m, 6 H), 3.87 (d, ³ J _H–H = 4.0 Hz, 2 H), 1.75 (t, ³ J _H–H = 4.0 Hz, 1 H). ¹³CNMR (100 MHz, CDCl₃): δ = 28.70, 117.29, 118.34, 119.01, 122.77, 123.37, 129.76, 129.92, 143.11, 156.94, 157.50. ESI-HRMS: m/z calcd for C₁₃H₁₂OS [M + Na]⁺: 239.0609; found: 239.0611