Lithiation and functionalization of 1-alkynylimidazoles at the 2-position

A Convenient One-Pot Synthesis of 1-Aryl-Substituted 4-Iodopyrazol-3-Ols via Aromatisation and Oxidative Iodination Reactions

A convenient and economical one-pot synthesis of a series of new 1-aryl-substituted 4-iodopyrazole-3-ols from easily available pyrazolidin-3-ones in the presence of sodium iodide, 30% solution of hydrogen peroxide and a catalytic amount of sulfuric acid in dichloromethane via aromatisation and oxidative iodination reactions are described. This protocol has the advantages of high atom economy, cost-effectiveness, short reaction time and environmental friendliness.

Cytotoxic 1,2-dialkynylimidazole-based aza-enediynes: aza-Bergman rearrangement rates do not predict cytotoxicity

A new class of potential antitumor agents inspired by the enediyne antitumor antibiotics has been synthesized: the 1,2-dialkynylimidazoles. The aza-Bergman rearrangement of these 1,2-dialkynylimidazoles has been investigated theoretically at the B3LYP/6-31G(d,p) level and experimentally by measuring the kinetics of rearrangement in 1,4-cyclohexadiene. There is a good correlation between the theoretical and experimental results; subtle substituent effects on the initial aza-Bergman cyclization barrier predicted by theory are confirmed by experiment. Yet, despite the ability of these 1,2-dialkynylimidazoles to undergo Bergman rearrangement to diradical/carbene intermediates under relatively mild conditions, there is no correlation between the rate of Bergman cyclization and cytotoxicity to A459 cells. In addition, cytotoxic 1,2-dialkynylimidazoles do not cause nicking of supercoiled plasmid DNA or cleavage of bovine serum albumin. An alternative mechanism for cytotoxicity involving the unexpected selective thiol addition to the N-ethynyl group of certain 1,2-dialkynylimidazoles is proposed.

A divergent mechanistic course of Pd(0)-catalyzed aza-Claisen rearrangement and aza-Rautenstrauch-type cyclization of N-allyl ynamides

A fascinating mechanistic study of ynamido-palladium-pi-allyl complexes is described that features isolation of a unique silyl ketenimine via aza-Claisen rearrangement, which can be accompanied by an unusual thermal N-to-C 1,3-Ts shift in the formation of tertiary nitriles and a novel cyclopentenimine formation via a palladium-catalyzed aza-Rautenstrauch-type cyclization pathway.

A Stereoselective Intramolecular Cyclopropanation via a De Novo Class of Push-Pull Carbenes Derived from DMDO-Epoxidations of Chiral Ynamides

This work describes the first examples of diastereoselective intramolecular cyclopropanations of a de novo class of push-pull carbenes derived from DMDO-epoxidations of chiral ynamides. This reaction sequence essentially constitutes a tandem epoxidation-cyclopropanation that effectively gives arise to a series of structurally unique amido-cyclopropanes. A plausible mechanistic model is proposed revealing insights into this novel cyclopropanation process.

Synthesis and biological evaluation of p38alpha kinase-targeting dialkynylimidazoles

Based on the mild, thermal rearrangement of 1,2-dialkynylimidazoles to reactive carbene or diradical intermediates, a series of 1,2-dialkynylimidazoles were designed as potential irreversible p38 MAP kinase alpha-isoform (p38alpha) inhibitors. The synthesis of these dialkynylimidazoles and their kinase inhibition activity is reported. The 1-ethynyl-substituted dialkynylimidazole 14 is a potent (IC(50)=200 nM) and selective inhibitor of p38alpha. Moreover, compound 14 covalently modifies p38alpha as determined by ESI-MS after 12h incubation at 37 degrees C. The unique kinase inhibition, covalent kinase adduct formation, and minimal CYP450 2D6 inhibition by compound 14 demonstrate that dialkynylimidazoles are a new, promising class of p38alpha inhibitors.