Vinyltriphenylphosphonium salt-mediated preparation of thiophene-containing electron-poor alkenes from acetylenic esters, 2-thienylmethanol and triphenylphosphine
Protonation of the highly reactive 1:1 intermediates, produced in the reaction between triphenylphosphine and alkyl acetylenecarboxylates (methyl acetylenecarboxylate, ethyl acetylenecarboxylate and ethyl phenylacetylenecarboxylate) by 2-thienylmethanol leads to vinyltriphenylphosphonium salts, which undergo an addition-elimination reaction in CH2Cl2 at room temperature to produce the corresponding O-vinylated alkenes via thiophene-containing phosphorus ylides intermediates in fairly high yields. The structural analysis of all products indicated that the reactions are regio- and stereoselective.
KEY WORDS: 2-Thienylmethanol, Acetylenic ester, Vinyltriphenylphosphonium salt, O-Vinylation, Michael addition
Bull. Chem. Soc. Ethiop. 2011, 25(1), 91-96.