Accessing Bioactive Hydrazones by the Hydrohydrazination of Terminal Alkynes Catalyzed by Gold(I) Acyclic Aminooxy Carbene Complexes and Their Gold(I) Arylthiolato and Gold(III) Tribromo Derivatives: A Combined Experimental and Computational Study

[Image: see text] Hydrohydrazination of terminal alkynes with hydrazides yielding hydrazones 5–14 were successfully catalyzed by a series of gold(I) acyclic aminooxy carbene complexes of the type [{(4-R(2)-2,6-t-Bu(2)-C(6)H(2)O)(N(R(1))(2))}methylidene]AuCl, where R(2) = H, R(1) = Me (1b); R(2) = H, R(1) = Cy (2b); R(2) = t-Bu, R(1) = Me (3b); R(2) = t-Bu, R(1) = Cy (4b). The mass spectrometric evidence corroborated the existence of the catalytically active solvent-coordinated [(AAOC)Au(CH(3)CN)]SbF(6) (1–4)A species and the acetylene-bound [(AAOC)Au(HC≡CPhMe)]SbF(6) (3B) species of the proposed catalysis cycle. The hydrohydrazination reaction was successfully employed in synthesizing several bioactive hydrazone compounds (15–18) with anticonvulsant properties using a representative precatalyst (2b). The DFT studies favored the 4-ethynyltoluene (HC≡CPhMe) coordination pathway over the p-toluenesulfonyl hydrazide (NH(2)NHSO(2)C(6)H(4)CH(3)) coordination pathway, and that proceeded by a crucial intermolecular hydrazide-assisted proton transfer step. The gold(I) complexes (1–4)b were synthesized from the {[(4-R(2)-2,6-t-Bu(2)-C(6)H(2)O)(N(R(1))(2))]CH}(+)OTf(–) (1–4)a by treatment with (Me(2)S)AuCl in the presence of NaH as a base. The reactivity studies of (1–4)b yielded the gold(III) [{(4-R(2)-2,6-t-Bu(2)-C(6)H(2)O)(N(R(1))(2))}methylidene]AuBr(3) (1–4)c complexes upon reaction with molecular bromine and the gold(I) perfluorophenylthiolato derivatives, [{(4-R(2)-2,6-t-Bu(2)-C(6)H(2)O)(N(R(1))(2))}methylidene]AuSC(6)F(5) (1–4)d, upon treatment with C(6)F(5)SH.