Catalyst-Free Annulation of Acylethynylpyrroles with 1-Pyrrolines: A Straightforward Access to Tetrahydrodipyrrolo[1,2-a:1',2'-c]imidazoles.

Acylethynylpyrroles undergo facile (rt, MeCN or MeOH, 24-72 h) catalyst-free annulation with 1-pyrrolines to afford acylmethylenetetrahydrodipyrrolo[1,2-a:1',2'-c]imidazoles in up to 93% yield and 90% E-stereoselectivity of the olefin moiety.

Cyanoquinolines and Furo[3,4-b]quinolinones Formation via On-The-Spot 2,3-Functionalization of Quinolines with Cyanopropargylic Alcohols.

A convenient approach to 2-(1-ethoxyalkoxy)-3-cyanoquinolines (in up to 50% yields) has been developed. The approach comprises functionalization of quinolines with acetals of cyanopropargylic alcohols (KOH/H2O/MeCN, 55-60 °C) followed by their transformation to furo[3,4-b]quinolinones (in up to 98% yields) via the sequential removal of acetal protection and intramolecular cyclization/hydration (7% aqueous HCl, acetone, 20-25 °C).

Acylacetylenes in multiple functionalization of hydroxyquinolines and quinolones.

The expected one-pot multiple functionalization of hydroxyquinolines and quinolones with acylacetylenes (20 mol% KOH, 5 equiv. H2O, MeCN, 55-60 °C), which, according to the previous finding, might involve the addition of OH and NH-functions to the triple bond and insertion of acylacetylenes into the quinoline scaffold, retains mainly on the formation of chalcone-quinoline ensembles in up 99% yield. The higher functionalized quinolines can be obtained in a synthetically acceptable yield, when the above ensembles are treated with the second molecule of acylacetylenes. Thus, the further insertion of second molecule of the acetylenes into the quinoline scaffold occurs as a much slower process indicating a strong adverse substituent effect of the remote chalcone moiety.

Organometal-Free Arylation and Arylation/Trifluoroacetylation of Quinolines by Their Reaction with CF3-ynones and Base-Induced Rearrangement.

The reaction of quinolines with CF3-ynones resulted in the formation of 1,3-oxazinoquinolines. Subsequent treatment of the reaction mixture with a base initiated deep structural transformation of primary products. Both steps proceed in very high yield. As a result, unusual rearrangement of 1,3-oxazinoquinolines to form either 2-arylquinolines or 2-aryl-3-trifluoroacetylquinolines was discovered. The decisive role of the base in the reaction direction was shown. Using these reactions, highly efficient pathways to 2-arylquinolines and 2-aryl-3-trifluoroacetylquinolines were elaborated to provide the corresponding compounds in high yields using a simple one-pot procedure. The possible mechanism of rearrangement is discussed.

One-Pot Metal-Free Synthesis of 3-CF3-1,3-Oxazinopyridines by Reaction of Pyridines with CF3CO-Acetylenes.

The reaction of pyridines with trifluoroacetylated acetylenes was investigated. It was found that the reaction of various pyridines with two molecules of CF3CO-acetylenes proceeds under mild metal-free conditions. As a result, efficient stereoselective synthesis of 3-arylethynyl-3-trifluoromethyl-1,3-oxazinopyridines was elaborated. Target heterocycles can be prepared in up to quantitative yields.

Cyanoacetylenes as Triggers and Partners in KOH-Assisted Assemblies of Quinoline-Based Dihydropyrimido[1,2-a]quinolin-3-ones on Water.

Arylcyanoacetylenes trigger the assembly of dihydropyrimido[1,2-a]quinolin-3-ones in good to excellent yields on the platform of quinolines in the presence of KOH in aqueous media at room temperature. This green on-water methodology provides a simple one-pot access to a novel family of the pharmaceutically prospective compounds.

Stereoselective tandem ring opening of imidazoles with electron-deficient acetylenes and water: synthesis of functionalized (Z,Z)-1,4-diaza-2,5-dienes.

1-Substituted imidazoles undergo exceptionally facile stereoselective ring opening under the influence of electron-deficient acetylenes and water (equimolar ratio of the reactants) in MeCN at 45-60 °C without any catalysts to afford functionalized (Z,Z)-1,4-diaza-2,5-dienes, (Z,Z)-propenylaminoethenylformamides, in up to 80% yields. The reaction is rationalized to proceed in a tandem manner via zwitterionic vinyl carbanions formed by nucleophilic addition of imidazole to the triple bond. The carbanionic center is then quenched with water followed by the rearrangement of the intermediate 2-hydroxy-3-alkenylimidazolines.

A general synthetic strategy for the design of new BODIPY fluorophores based on pyrroles with polycondensed aromatic and metallocene substituents.

BODIPYrrole: A general strategy for the design of novel BODIPY fluorophores based on pyrroles with polycondensed aromatic and metallocene substituents has been developed. The strategy involves the acylation of the condensed substituent and treatment of the acylated derivative (as oxime) with acetylene in MOH/DMSO (M = alkali metal) to give pyrroles that were then used for assembly of the BODIPY fluorophores (see scheme).

Stereoselective C(2)-vinylation of 1-substituted imidazoles with 3-phenyl-2-propynenitrile.

First examples of direct vinylation of 1-substituted imidazoles at the 2-position of the imidazole nucleus are described. 1-Substituted imidazoles 1a-e are C(2)-vinylated with 3-phenyl-2-propynenitrile (2) at room temperature without catalyst and solvent to afford 3-(1-organyl-1H-imidazol-2-yl)-3-phenyl-2-propenenitriles 3a-e, mainly (c.a. 95%) as (Z)-isomers, in 56-88% yield. The reaction is likely to involve the zwitterionic intermediates, which prototropically isomerizes to imidazole carbene and eventually undergoes the selective 3,2-shift of the functionalized vinyl substituent.