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The synthesis of novel substituted pyrroloquinolinones is described by concomitant ring contraction cyclization form 2-(2-amino-5-nitro-phenyl)-[4 H ]-1,3-thiazines, which were derived from N -substituted 5-nitro-anthranilonitrile. An easy access to novel 4-thiono-1,4-dihydro-1,3-quinazoline heterocycles is also mentioned.

The electrochemical two electron reduction of pyridazines, substituted by electron withdrawing groups, primarily lead to their corresponding 1,2-dihydro-derivatives. Depending on the nature of the ring substitution, these intermediates can either rearrange into 1,4-dihydro-pyridazines, or undergo electrochemical reduction to give rise to activated pyrroles by a ring contraction reaction with extrusion of nitrogen. Another way of access to the latter has been achieved by a disproportionation reaction of 1,2-dihydro-pyridazines, leading directly to the expected pyrroles and recovery of 50% of pyridazines.

The bielectronic electrochemical reduction of pyridazines, substituted by electron-withdrawing groups, leads to their corresponding 1,2-dihydro derivatives. Depending on the nature of the ring substitution, these intermediates can either rearrange into 1,4-dihydropyridazine isomers or be further electrochemically reduced into activated pyrroles.

The preparation of 2-phenyl-4-dimethylamino-1-aza-, 1-oxa-, 1-thia-, 1-selena-3-azabuta-1,3-dienes as well as their 4-methyl derivatives is described following a new heteroatom interchange reaction process. Heteronucleophilic attack at one particular reactive site of bis-electrophilic amidinium salts is the key feature of the process. In addition, we also disclose that the substituted 1-oxa-3-aza- and 1,3-diazabuta-1,3-dienes can be obtained by a reactional transformation cascade initiated by either silver acetate addition or tosyl azide [3+2] cycloaddition onto the CS or CSe double bonds of the 1-thia- and 1-selena-3-azabuta-1,3-diene analogues.

International audience; Synthesis of alternating pyridine-pyrrole molecular strands composed of two electron-rich pyrrole units (donors) sandwiched between three pyridinic cores (acceptors) is described. The envisioned strategy was a smooth electrosynthesis process involving ring contraction of corresponding tripyridyl-dipyridazine precursors. 2,6-Bis[6-(pyridazin-3-yl)]pyridine ligands 2a-c bearing pyridine residues at the terminal positions were prepared in suitable quantities by a Negishi metal cross-coupling procedure. The yields of heterocyclic coupling between 2-pyridyl zinc bromide reagents 12a-c and 2,6-bis(6-trifluoromethanesulfonylpyridazin-3-yl)pyridine increased from 68 to 95% following introduction of electron-donating methyl groups on the metallated halogenopyridine units. Favorable conditions for preparative electrochemical reduction of tripyridyl-dipyridazines 2b,c were established in THF/acetate buffer (pH 4.6)/acetonitrile to give the targeted 2,6-bis[5-(pyridin-2-yl)pyrrol-2-yl]pyridines 1b and 1c in good yields. The absorption behavior of the donor-acceptor tripyridyl-dipyrrole ligands was evaluated and compared to theoretical calculations. Highly fluorescent properties of these chromophores were found (ν(em)≈2 × 10(4) cm(-1) in MeOH and CH(2)Cl(2)), and both pyrrolic ligands exhibit a remarkable quantum yield in CH(2)Cl(2) (φ(f)=0.10). Structural studies in the solid state established the preferred cis conformation of the dipyrrolic ligands, which adopting a planar arrangement with an embedded molecule of water having a complexation energy exceeding 10 kcal mol(-1). The ability of the tripyridyl-dipyrrole to complex two copper(II) ions in a pentacoordinate square was investigated.

The preparation of 2-phenyl-4-dimethylamino-1-aza-, 1-oxa-, 1-thia-, 1-selena-3-azabuta-1,3-dienes as well as their 4-methyl derivatives is described following a new heteroatom interchange reaction process. Heteronucleophilic attack at one particular reactive site of bis-electrophilic amidinium salts is the key feature of the process. In addition, we also disclose that the substituted 1-oxa-3-aza- and 1,3-diazabuta-1,3-dienes can be obtained by a reactional transformation cascade initiated by either silver acetate addition or tosyl azide [3+2] cycloaddition onto the CS or CSe double bonds of the 1-thia- and 1-selena-3-azabuta-1,3-diene analogues.

The bielectronic electrochemical reduction of pyridazines, substituted by electron-withdrawing groups, leads to their corresponding 1,2-dihydro derivatives. Depending on the nature of the ring substitution, these intermediates can either rearrange into 1,4-dihydropyridazine isomers or be further electrochemically reduced into activated pyrroles.

Two studies, concerning the synthesis of original nucleoside analogs regarded as an application of heterochemistry on thiaazaheterocycle systems from thiaazabutadienes are discussed. The preparation of new N- and C-nucleosides is presented. In the second part, the discovery of aromatic polycyclic derivatives as inhibitors of Tat protein is exposed. The work presented takes into account the participation of African partners in further synthetic research programs carried out in collaboration with the laboratory of Nantes.