Gianfranco Favi

Synthesis of functionalized pyrroles via catalyst- and solvent-free sequential three-component enamine-azoene annulation.

A new and efficient synthesis of polysubstituted pyrroles by a sequential one-pot three-component reaction between primary aliphatic amines, active methylene compounds, and 1,2-diaza-1,3-dienes (DDs) is reported. The reactions were performed without catalyst and under solvent-free conditions with complete control of pathway selectivity. Notably, the ready availability of the starting materials and the high level of practicability of the reaction and work up make this approach an attractive complementary method for access to unknown polysubstituted pyrroles.

Copper(II)/Copper(I)-Catalyzed Aza-Michael Addition/Click Reaction of in Situ Generated α-Azidohydrazones: Synthesis of Novel Pyrazolone−Triazole Framework

A one-pot Cu(II)-catalyzed aza-Michael addition of trimethylsilyl azide to 1,2-diaza-1,3-dienes and Cu(I)-catalyzed 1,3-dipolar cycloaddition of in situ generated alpha-azidohydrazones with alkynes is reported. This process combining two consecutive steps with recycling of the catalyst (Cu(OAc)(2).H(2)O) represents a useful protocol for the smooth synthesis of novel pyrazolone-triazole derivatives.

A novel solvent-free approach to imidazole containing nitrogen-bridgehead heterocycles.

A very simple domino reaction under solvent-free conditions of various pyridine-like heterocycles with 1,2-diaza-1,3-dienes produces in good yields imidazo[1,2-a]pyridines, imidazo[1,2-a]quinolines, and imidazo[2,1-a]isoquinolines. The advantage of this one-pot transformation lies in the use of simple pyridine-like compounds without prefunctionalization of the starting heterocycles.

An Efficient One-Pot, Three-Component Synthesis of 5-Hydrazinoalkylidene Rhodanines from 1,2-Diaza-1,3-dienes

A novel three-component synthesis of 5-hydrazinoalkylidene rhodanine derivatives starting from aliphatic primary amines, carbon disulfide, and 1,2-diaza-1,3-dienes is described. The reaction proceeds successfully under both solution and solid-phase conditions.

A Novel and Convenient Protocol for Synthesis of Pyridazines

A new flexible strategy for the synthesis of diversely functionalized pyridazines from 4-chloro-1,2-diaza-1,3-butadienes and active methylene compounds is reported. The high chemoselectivity of this approach offers access to structural precursors of GABA-A antagonist analogues.

Interceptive [4 + 1] annulation of in situ generated 1,2-diaza-1,3-dienes with diazo esters: direct access to substituted mono-, bi-, and tricyclic 4,5-dihydropyrazoles.

In situ derived acyclic and cyclic 1,2-diaza-1,3-dienes (DDs) were engaged in interceptive [4 + 1] annulation strategy with diazo esters (DEs). The catalytic activity of inexpensive copper(II) chloride allows the direct synthesis of mono-, bi-, and tricyclic 4,5-dihydropyrazole-5-carboxylic acid derivatives in a process that circumvents the use of an anhydrous and inert atmosphere.

Flexible protocol for the chemo- and regioselective building of pyrroles and pyrazoles by reactions of Danishefsky's dienes with 1,2-diaza-1,3-butadienes.

The versatility of the Mukaiyama-Michael-type addition/heterocyclization of Danishefskys diene with 1,2-diaza-1,3-butadienes was applied to the synthesis of both 4 H-1-aminopyrroles and 4,5 H-pyrazoles. Thus, the same reagents furnished different types of highly functionalized azaheterocycles essentially depending on their structure: as a matter of fact, R1 = COOR or CONR 2 differently affects the acidity of the proton at the adjacent carbon. An unexpected formation of 5 H-1-aminopyrroles from the reactions carried out in water was also observed.

One-Pot Synthesis of Imidazole-4-Carboxylates by Microwave-Assisted 1,5-Electrocyclization of Azavinyl Azomethine Ylides.

Diversely functionalized imidazole-4-carboxylates were synthesized by microwave-assisted 1,5-eletrocyclization of 1,2-diaza-1,3-diene-derived azavinyl azomethine ylides. 1,2-Diaza-1,3-dienes were treated with primary aliphatic or aromatic amines and subjected to microwave irradiation in the presence of aldehydes. 3-Alkyl- and 3-arylimidazole-4-carboxylates were prepared in good yields through a one-pot multicomponent procedure. Modulation of the substituents at C-2, N-3 and C-5 was possible, and 2-unsubstituted imidazoles were obtained when paraformaldehyde was used.

Divergent construction of pyrazoles via Michael addition of N-arylhydrazones to 1,2-diaza-1,3-dienes.

The base (NaH)-promoted Michael addition of N-arylhydrazones (AHs) with 1,2-diaza-1,3-dienes (DDs) produces unprecedented β-azohydrazone adducts. Strategically, the use of AHs as acyl anion equivalents (d(1) synthon) and DDs as α-electrophiles (a(2) synthon) of carbonyl compounds open the way to two important classes of pyrazole compounds.

Powerful approach to heterocyclic skeletal diversity by sequential three-component reaction of amines, isothiocyanates, and 1,2-diaza-1,3-dienes.

By highly efficient, one-pot, three-component reactions, combining one set of 1,2-diaza-1,3-dienes (DDs), primary amines, and isothiocyanates in a different sequential order of addition, heterocyclic skeletal diversity can be achieved. The key feature discriminating the different heterocyclic core formation is the availability of the N or S heteronucleophile to give the first Michael addition step affording regioselective substituted 2-thiohydantoins or 2-iminothiazolidinones. The hydrazone or enehydrazino side chain at the 5-position of both heterocycles represents a valuable functionality to reach novel 5-hydroxyethylidene derivatives difficult to obtain by other methods.