10.1021/om010672d.s001 Victorio Cadierno Victorio Cadierno Salvador Conejero Salvador Conejero M. Pilar Gamasa M. Pilar Gamasa José Gimeno José Gimeno Miguel A. Rodríguez Miguel A. Rodríguez Activation of Propargylic Alcohols Derived from Hormonal Steroids by the Indenyl−Ruthenium(II) Complex [RuCl(η<sup>5</sup>-C<sub>9</sub>H<sub>7</sub>)(PPh<sub>3</sub>)<sub>2</sub>]:  Experimental and Theoretical Evidence of an Allenylidene−Vinylvinylidene Equilibrium American Chemical Society 2001 Ru Theoretical Evidence nucleophilic addition PMe 2 Ph electrophilic C γ atom RuCl allenylidene 3 Hormonal Steroids vinylvinylidene tautomer disubstituted vinylvinylidene complexes 6 PH vinylvinylidenes 4 vinylvinylidene 4 NaPF 6 kcal reaction mixtures equilibrium mixtures Propargylic Alcohols Derived PPh allenylidenes 3 Ab initio MeOSO 2 CF 3 tautomerization process K 2 CO 3 activation energy 2001-12-11 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Activation_of_Propargylic_Alcohols_Derived_from_Hormonal_Steroids_by_the_Indenyl_Ruthenium_II_Complex_RuCl_sup_5_sup_-C_sub_9_sub_H_sub_7_sub_PPh_sub_3_sub_sub_2_sub_Experimental_and_Theoretical_Evidence_of_an_Allenylidene_Vinylvinylidene_Equilibrium/3767157 The indenyl−ruthenium(II) complex [RuCl(η<sup>5</sup>-C<sub>9</sub>H<sub>7</sub>)(PPh<sub>3</sub>)<sub>2</sub>] (<b>1</b>) reacts with ethisterone (<b>2a</b>), 17α-ethynylestradiol (<b>2b</b>), and mestranol (<b>2c</b>), in methanol and in the presence of NaPF<sub>6</sub>, to afford equilibrium mixtures containing the corresponding allenylidene <b>3a</b>−<b>c</b> and vinylvinylidene <b>4a</b>−<b>c</b> tautomers. Deprotonation of these mixtures with K<sub>2</sub>CO<sub>3</sub> allows the preparation of σ-enynyl derivatives <b>5a</b>−<b>c</b>, which can be selectively alkylated with MeOSO<sub>2</sub>CF<sub>3</sub> to yield disubstituted vinylvinylidene complexes <b>6a</b>−<b>c</b>. Displacement of these equilibriums can also be accomplished by treatment of the reaction mixtures with acetonitrile or PMe<sub>2</sub>Ph. Thus, while in the first case terminal 1,3-enynes <b>7a</b>−<b>c</b> are selectively obtained by demetalation of vinylvinylidenes <b>4a</b>−<b>c</b>, phosphonio-alkynyl complexes <b>9a</b>−<b>c</b> are exclusively formed in the second case as the result of the nucleophilic addition of PMe<sub>2</sub>Ph on the electrophilic C<sub>γ</sub> atom of allenylidenes <b>3a</b>−<b>c</b>. Ab initio molecular orbital calculations on the models [Ru{CCC(H)CH<sub>3</sub>}(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)(PH<sub>3</sub>)<sub>2</sub>]<sup>+</sup> and [Ru{CC(H)CHCH<sub>2</sub>}(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)(PH<sub>3</sub>)<sub>2</sub>]<sup>+</sup> show that the vinylvinylidene tautomer is only 2.1 kcal/mol more stable than the allenylidene. The spontaneous tautomerization process between both complexes, which involves a [1,3]-hydrogen sigmatropic rearrangement, requires an activation energy of 66.5 kcal/mol.