Alkyl and aryl sulfides react with equimolecular amounts of p-toluenesulfonylacetylene in CH3CN at 0 degrees C or rt without the use of any catalytic reagent to give good yields of Z-2-sulfanylvinylsulfonyl derivatives with total diastereoselectivity. On the other hand, in the presence of 1.1 equiv of NaH in THF, the same reaction affords the corresponding E-diastereomer also with total diastereoselectivity.
Thioethers
Thioethers Q 0580Chemoselective Protection of Thiols versus Alcohols and Phenols. The Tosvinyl Group. -Addition of tosylacetylene (II) to aliphatic and aromatic thiols proceeds stereoselectively to give the Z-tosyl vinyl derivatives almost exclusively. Furthermore, reactions with the hydroxythiols (VI) proceed chemoselectively. Application to α-amino acids show that the side-chain of the cysteine derivative (VIII) is protected selectively in the presence of analogous serine and tyrosine derivatives. The tosyl vinyl group can be removed with pyrrolidine (addition-elimination mechanism) or by a thiolate exchange as exemplified for (Va). -(ARJONA*, O.; MEDEL, R.; ROJAS, J.; COSTA, A. M.; VILARRASA, J.; Tetrahedron Lett. 44 (2003) 34, 6369-6373; Dep. Quim. Org., Fac. Cienc. Quim., Univ. Complutense, E-28040 Madrid, Spain; Eng.) -Roy 47-090
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