[W(CO)5]-catalyzed endo- or exo-cycloisomerization reactions of 1,1-disubstituted 4-pentyn-1-ols:: Experimental and theoretical studies

The [W(CO)(5)]-catalyzed cy-cloisomerization reaction of 1,1-disubstituted 4-pentyn-1-ol derivatives has been studied from both, an experimental and theoretical point of view. Three different catalytic systems have been evaluated [preformed [(thf)W(CO)(5)], [W(CO)(6)]/excess Et3N, and [W(CO)(6)]/ 2 mol % Et3N]. We have found that the reaction proceeds to give the formal endo- or exo-cycloisomerization products depending on the amount of Et3N used and on the substitution along the alkyl chain of the starting alkynol. ne theoretical study allowed us to find the mechanisms of the reactions which explain the formation of the formal endo-or exo-cycloisomerization products.