Daniel Mendoza-Espinosa

Versatile O- and S-functionalized 1,2,3-triazoliums: ionic liquids for the Baylis–Hillman reaction and ligand precursors for stable MIC-transition metal complexes

The efficient synthesis of O- and S-functionalized 1,2,3-triazoliums is reported. Owing to their physical properties, these cations are efficient ionic liquids for Baylis–Hillman addition under mild reaction conditions. Simultaneously, the functionalization of the triazolium rings allows for the in situ C-5 metallation providing air stable triazol-5-ylidene Rh(I) Au(I), and Pd(II) complexes. The present work constitutes a rare example of versatile triazolium salts capable of serving in two unrelated synthetic procedures.

Facile One-Pot Synthesis of 1,2,3-Triazoles Featuring Oxygen, Nitrogen, and Sulfur Functionalized Pendant Arms

Abstract A practical and efficient one-pot synthesis of novel 1,2,3-triazoles featuring nitrogen, oxygen, and sulfur functionalized pendant arms has been developed. The click reaction of mono-propargyl derivatives supported by aniline, thiophenol, and benzyl alcohol, with sodium azide and p-substituted benzyl halogenides, renders a series of N-substituted-1,2,3-triazoles in good yields under mild reaction conditions. The catalyst system was based in Cu(OAc)2 · H2O, sodium L-ascorbate, and 1,10-phenanthroline monohydrate, and all reactions were performed in a mixture H2O–ethanol (4:1 v/v). Additionally, the preparation of bis-1,2,3-triazoles supported by di-propargylated aniline was carried out, demonstrating the versatility of the present methodology. [Supplementary materials are available for this article. Go to the publishers online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.] GRAPHICAL ABSTRACT

Visible-Light-Promoted Au(I) to Au(III) Oxidation in Triazol-5-ylidene Complexes.

Reaction of triazolium precursors [MIC(CH2 )n - H+ ]I- (n=1-3) with potassium hexamethyldisilazane (KHMDS) and AuCl(SMe2 ) generates the gold(I) complexes of the type MIC(CH2 )n ⋅AuI. Visible light exposure of the latter complexes promotes a spontaneous disproportionation process rendering gold(III) complexes of the type [{MIC(CH2 )n }2 ⋅AuI2 ]+ I- . Both the AuI and AuIII complex series were tested in the catalytic hydrohydrazination of terminal alkynes using hydrazine as nitrogen source.

Electrochemical assessment of phenol and triazoles derived from phenol (BPT) on API 5L X52 steel immersed in 1 M HCl

The corrosion inhibition of phenol triazoles was tested with several halogens by means of electrochemical impedance and potentiodynamic polarization. We observed the importance of the 1,2,3-triazole ring in the chemical structure because significant inhibition efficiencies (η) > 90% were achieved at low concentrations with the different halogens. These compounds have a physisorption-type adsorption process, in accordance with the Langmuir model. For long immersion times, the organic inhibitor BPTI showed good corrosion protection during 504 hours of immersion with η > 80%. Furthermore, the hydrodynamic conditions proved that organic molecules experience a desorption process related to the different rotation velocities employed. Finally, it was demonstrated by SEM that the corrosion velocity is diminished when using the BPTI inhibitor at 50 ppm.

Chrysin functionalized NHC–Au(I) complexes: synthesis, characterization and effects on the nematode Caenorhabditis elegans

Following a direct quaternarization protocol, the preparation and full characterization of a series of chrysin derived imidazolium salts (2a–d) are reported. Deprotonation of the latter with potassium hexamethyldisilazide (KHMDS) followed by in situ metalation with AuCl(SMe2) allowed for the synthesis of a series Au(I) imidazol-2-ylidene metal complexes (3a–d) in one step. All metal complexes were properly characterized by means of NMR spectroscopy, FT-IR, and elemental analyses. Crystal structures of complexes 3b and 3c illustrate the metal center geometrical environment and the spatial disposition of the mesityl and chrysin flanking groups in the NHC ligands. We tested if gold(I) complexes 3a–d elicit any biological effect on the nematode Caenorhabditis elegans observing that 3a and 3c inhibited the rate of egg laying, whereas 3b and 3d did not, in contrast 3d reduce body width of the nematode. The imidazolium salts did not show an apparent effect on the anatomy of the worms although 2a reduced the egg-laying rate.

Activation of aldehydes by exocyclic iridium(I)-η4:π2-diene complexes derived from 1,3-oxazolidin-2-ones

The Ir(i) complexes [TpMe2Ir(η4-1,4-diene)] 2b and 2c react thermally with a variety of aromatic aldehydes, 3a-e, to generate the metallabicyclic compounds 4e-k and the Fischer-type carbenes 5a-b in moderate yields. These reactions are proposed to take place with the initial formation of η1-aldehyde adducts as key intermediates. The formation of the metallabicyclic compounds 4e-k involves a formal decarboxylation process at the exo-2-oxazolidinone diene and an ortho metallation of the aromatic ring. The generation of the Fischer-type carbenes 5a-b is the result of a series of metal-based rearranged intermediates with no decarboxylation observed. Treatment of the η4-diene complex 2b with a variety of Lewis bases induces a change in the binding mode of the diene ligand from η4:π2 to η2:σ2 to form the Ir(iii) derivatives 6b-d of composition TpMe2Ir-(η4:π2-1,4-diene)(L) (L = CO, MeCN, and C5H5N). A study of reactions of complex 2b with either mono- or poly-deuterated aldehydes was performed to understand the mechanisms of such processes. The results of these studies were used to determine plausible formation mechanisms of the metallabicyclic compounds 4e-4k and Fischer-type carbenes 5a-b compound series. These mechanisms were corroborated by density functional theory (DFT) calculations of the free energy profiles.

Pseudo-four component synthesis of mono- and di-benzylated-1,2,3-triazoles derived from aniline.

The pseudo-four component click synthesis of dibenzylated 1,2,3-triazoles derived from aniline is reported. The cycloaddition of sodium azide to N-(prop-2-ynyl)-benzenamine (I) in the presence of equimolar amounts of p-substituted benzyl derivatives, yields a mixture of mono- and dibenzylated 1,2,3-triazoles. When two equivalents of the benzyl derivative are added to the multicomponent reaction, the selective preparation of the dibenzylated compounds is achieved. The reactivity of the aniline N-H bond in monobenzylated 1,2,3-triazoles was tested by treatment with one equivalent of a p-substituted benzyl chloride at 40 °C, rendering the dibenzylated derivatives quantitatively.