Synlett 2005(20): 3063-3066  
DOI: 10.1055/s-2005-921922
LETTER
© Georg Thieme Verlag Stuttgart · New York

Regio- and Enantioselective Ring-Opening of Epoxides with HMDST: A Straightforward Access to 1,2-Mercaptoalcohols

Alessandro Degl’Innocenti*a, Antonella Capperucci*a, Arianna Cerretia,b, Salvatore Pollicinob, Serena Scapecchic, Irene Malescia, Giulio Castagnolia
a Dipartimento di Chimica Organica, Università di Firenze, Via della Lastruccia 13, 50019 Sesto Fiorentino, Italy
b Dipartimento di Chimica Organica, ‘A. Mangini’, viale Risorgimento 4, 40136 Bologna, Italy
c Dipartimento di Scienze Farmaceutiche, Università di Firenze, via Ugo Schiff 6, 50019 Sesto Fiorentino, Italy
Fax: +39(055)4573585; e-Mail: alessandro.deglinnocenti@unifi.it;
Further Information

Publication History

Received 14 September 2005
Publication Date:
28 November 2005 (online)

Abstract

TBAF-catalyzed reaction of a range of substituted ­epoxides with hexamethyldisilathiane smoothly affords a direct and simple access to β-mercaptoalcohols in a highly regio- and stereoselective way.

17

Typical Procedure: A solution of 2-methyloxirane (1a, 100 mg, 1.72 mmol) and HMDST (470 µL, 2.24 mmol, 398 mg) in THF (0.1 mL) was treated at r.t. with TBAF (1 M in THF; 450 µL, 0.45 mmol) under an inert atmosphere. The mixture became bright green and after 5 min pale yellow. The reaction was carried out for 30 min and the progress of the reaction monitored by TLC. After addition of citric acid (50% aq solution; 0.5 mL) the mixture was stirred for 5 min, then diluted with Et2O. The organic phase was then washed with citric acid (20% aq solution), extracted with Et2O, and dried over Na2SO4. Evaporation of the solvent afforded 106 mg of 1-mercaptopropan-2-ol (2a; 65%), which was pure enough to be used without further purification. 1H NMR (200 MHz, CDCl3): δ = 1.25 (3 H, d, J = 6.0 Hz), 1.43 (1 H, app t, J = 8.7 Hz), 2.32 (1 H, br s), 2.44-2.56 (1 H, m), 2.60-2.71 (1 H, m), 3.71-3.84 (1 H, m). 13C NMR (50 MHz, CDCl3): δ = 21.7, 33.2, 68.4. MS: m/z (%) = 92 (0.08), 91 (0.25), 75 (11), 45 (100).
Following the above procedure, oxirane 1a and HMDST were treated with a solution of TBAF (225 µL, 0.22 mmol)to give cleanly 2-(trimethylsilyloxy)propane-1-thiol (3a; 203 mg, 72% yield). 1H NMR (200 MHz, CDCl3): δ = 0.14 (9 H, s), 1.22 (3 H, d, J = 6.0 Hz), 1.46 (1 H, dd, J = 9.0 Hz, J = 8.8 Hz), 2.43-2.59 (2 H, m), 3.84 (1 H, app sextet). 13C NMR (50 MHz, CDCl3): δ = 0.2, 22.5, 33.3, 70.0. MS: m/z (%) = 164 (0.6), 149 (10), 117 (66), 91 (15), 75 (53), 73 (100).