Synlett
DOI: 10.1055/s-0039-1689925
letter
© Georg Thieme Verlag Stuttgart · New York

Aminoxylation of Thioalkynes through Radical-Polar Crossover

Giovanni Di Mauro
,
Martina Drescher
,
Sara Tkaczyk
,
Generous funding by the European Research Council (Grant No. CoG VINCAT 682002) and the Austrian Science Fund (FWF, Grant No. P32206) is acknowledged.
Further Information

Publication History

Received: 06 March 2019

Accepted after revision: 10 May 2019

Publication Date:
03 June 2019 (eFirst)

Published as part of the ISySyCat2019 Special Issue

Abstract

A one-pot procedure for the aminoxylation of thioalkynes for the direct formation of α-functionalized thioesters under mild reaction conditions is reported. A ketenethionium ion is the key intermediate, which is generated in situ by Brønsted acid mediated protonation and undergoes a radical-polar crossover.

Supporting Information

 
  • References and Notes

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  • 11 General Procedure for the Synthesis of 2 To a solution of the thioalkyne (1.00 equiv) in CH2Cl2 (0.1 M) in a flame-dried Schlenk tube, trifluoromethanesulfonic acid (1.10 equiv) was added, and the mixture was stirred for 15 min at 0°C. TEMPO (3.00 equiv) was added in one portion, and the resulting solution was allowed to warm up to 25 °C and stirred over 16 h. The reaction was quenched by addition of a saturated aqueous solution of NaHCO3. The product was extracted with CH2Cl2, and the resulting organic phase was dried over Na2SO4, filtered, and the solvent was evaporated under reduced pressure. The product was purified by flash chromatography on silica gel using heptane methyl-tert-butyl ether as eluent.
  • 12 Analytical Data for Compound 2c 1H NMR (400 MHz, CDCl3): δ = 3.75 (d, J = 8.8 Hz, 1 H), 2.28 (s, 3 H), 1.65–1.40 (br, 6 H), 1.30 (br, 3 H), 1.18 (br, 6 H), 1.12–1.06 (m, 1 H), 1.03 (br, 3 H) 0.75–0.45 (m, 4 H). 13C NMR (151 MHz, CDCl3): δ = 201.4, 94.5, 40.3 (2 C), 34.4, 33.5, 20.4, 20.1, 17.1, 15.1, 10.9, 7.5, 2.05 (quaternary carbons in the TEMPO moiety not visible in 13C NMR). HRMS (ESI+): m/z calcd for (C15H28N2OS+) [M + H]+: 286.1835; found: 286.1830. IR (neat): νmax = 3005, 2972, 2929, 2359, 1684, 1465, 1376, 900 cm–1.