Chemoselective protection of thiols versus alcohols and phenols. The Tosvinyl group

✍ Scribed by Odón Arjona; Rocı́o Medel; Jenny Rojas; Anna M. Costa; Jaume Vilarrasa

• Publisher: Elsevier Science
• Year: 2003
• Tongue: French
• Weight: 107 KB
• Volume: 44
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(03)01614-9

✦ Synopsis

The conjugate addition of aliphatic and aromatic thiols to ethynyl p-tolyl sulphone (tosylacetylene) has been managed to afford Tosvinyl derivatives chemoselectively (in the presence of oxygen nucleophiles) and stereoselectively (isomers Z) in practically quantitative yields. The conditions of choice are: catalytic amounts of Et 3 N (only 0.5-1.0 mol%), a reaction temperature around 0°C and, for the less acidic thiols, CF 3 CH 2 OH or CH 3 CN/CF 3 CH 2 OH as the solvent. Thus, N-Boc-Cys-OMe has been quantitatively protected as its S-Tosvinyl derivative in the presence of N-Boc-Ser-OMe and N-Boc-Tyr-OMe. This novel protecting group is stable to several basic and acidic conditions; its removal is achieved at rt by treatment with an excess of pyrrolidine or at 0°C with alkanethiolate ions.