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

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 choic...

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Bibliographic Details
Published in:Tetrahedron letters 2003-08, Vol.44 (34), p.6369-6373
Main Authors: Arjona, Odón, Medel, Rocı́o, Rojas, Jenny, Costa, Anna M., Vilarrasa, Jaume
Format: Article
Language:English
Subjects:
1-(ethynylsulfonyl)-4-methylbenzene (tosylacetylene)
addition reactions to triple bonds
thiol protecting group
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Summary: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 3N (only 0.5–1.0 mol%), a reaction temperature around 0°C and, for the less acidic thiols, CF 3CH 2OH or CH 3CN/CF 3CH 2OH 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. Graphic
ISSN:0040-4039
1873-3581
DOI:10.1016/S0040-4039(03)01614-9