77213-80-0Relevant articles and documents
Preparations et heterocyclisations nucleophiles de thiols acetyleniques
Dupuy, Claude,Surzur, Jean-Marie
, p. 353 - 360 (2007/10/02)
Acetylenic thiols HCC(CH2)nSH 1a and HCCCH2Y(CH2)2SH 1b, isolated or prepared in situ from the corresponding thiouronium salts, have been treated with alkali to induce cyclization by intramolecular nucleophilic addition of the thiolate to the triple bond.Starting from the thiol 1a (n = 2) we only isolated thiacyclopent-2-ene 2a, which results from addition to the terminal carbon of the triple bond (yield 45 percent).Higher homologues 1a (n = 3,4), on the other hand, exclusively led to the heterocyclic products 3a resulting from addition to the non-terminal carbon of the triple bond.The best yield was obtained with 1a (n = 3), which led to 2-methylenethiacyclopentane 3a (n = 3) with a 59 percent yield.With the thiol 1a (n = 4), the yield was only 20 percent for 2-methylenethiacyclohexane 3a (n = 4), and with 1a (n = 5) only polymers were formed.When Y = S or N-n-Bu, the substrates 1b behaved like their carbon homologues 1a (n = 3) : yields were in the same range, and the seven-membered heterocycle 2b resulting from attack on the terminal carbon of the triple bond could not be detected.On the other hand, substance 1b (Y = O) mainly led to the seven-membered ring compound 2b.Furthermore, the presence of the heteroatom Y enhanced the possibility of prototropic rearrangement of the triple bond, leading to the new heterocycle 4b in appreciable amounts for Y = O,S.Generally speaking, acetylenic thiolates behave similarly to acetylenic alkoxides, and the same tentative interpretations can be put forward to account for the results obtained.
