Nelly Plé

V-Shaped 4,6-Bis(arylvinyl)pyrimidine Oligomers: Synthesis and Optical Properties

A series of V-shaped 4,6-bis(arylvinyl)pyrimidines have been efficiently prepared by aldol condensation between 4,6-dimethylpyrimidine and the appropriate aromatic aldehyde. The methodology also proved successful when dendritic first generation poly(phenylenevinylene) aldehydes were used. Moreover, asymmetrically functionalized molecules were also obtained by the stepwise incorporation of arms in a controlled manner. The optical absorption and emission properties of these systems were studied in different solvents and media. The materials display strong emission solvatochromism that is reflected by a large red shift in their fluorescence emission maxima on increasing the solvent polarity. This change is accompanied by a successive decrease in fluorescence intensity. This behavior suggests a highly polar emitting state, which is characteristic of compounds that undergo an internal charge transfer upon excitation. The abilities of these molecules to function as colorimetric and luminescence pH sensors were demonstrated with dramatic color changes and luminescence switching upon the introduction of acid.

Incorporation of pyridazine rings in the structure of functionalized π-conjugated materials

Throughout the past few decades, the development of new π-conjugated organic compounds has received a lot of attention due to their potential applications ranging from liquid crystals, light-emitting and nonlinear optical applications to self-assembly and supramolecular chemistry. Most of these applications rely on electron transfer (ET) and excitation energy transfer (EET). Introduction in these conjugated structures of N-heterocycles such as the highly electronegative pyridazine ring appeared particularly interesting since the π-deficient character of the pyridazine, used as a dipolar moiety, favored the electron transfer. Moreover, the presence of nitrogen atoms with free electron pairs allows the pyridazine ring to act like as an effective and stable complexing agent for transition metal ions and to be used in supramolecular chemistry for the construction of highly sophisticated architectures. This review highlights recent π-conjugated materials including pyridazine ring and their applications in various fields.

Synthesis of 4,8-Diarylcinnolines and Quinazolines with Potential Applications in Nonlinear Optics. Diazines. Part 28

Abstract New 4,8-diarylbenzodiazines have been synthesized using cross-coupling reactions and regioselective metalation at the periposition C8 of the benzene moiety of various cinnolines and quinazolines. Some of these compounds have been tested to assess their nonlinear optical properties.

First metallation of iodo diazines. Iodo and nitrogen directed metallations. Diazines XXII

Abstract Lithiation of iodopyrazine and 4-iodo-2-methylthiopyrimidine followed by reaction with various electrophiles was successfully achieved and was used to synthesize new pyrazine and pyrimidine derivatives. Iodo and nitrogen directed metallations were observed.

Functionalization by metalation of the benzene moiety of benzodiazines. Determination of structures by long-range 1H-15N correlation at natural abundance. Diazines XXV

Abstract The first lithiation of the benzene moiety of various quinazolinones, quinoxalines, and phthalazines has been performed. The effects of kind and positions of various directing groups towards the regioselectivity of the metalation have been studied. Unambiguous structure determinations of quinoxaline derivatives have been carried out by applying NMR GHMBC 1 H- 15 N sequence.

Metalation of diazines X : First halogen migration during metalation of pyrimidines Unusual halogen-lithium exchange with LTMP new synthesis of Leshmaniacides

Abstract An halogen migration of iodine during the metalation of pyrimidines has been highlighted and a mechanism is proposed. An unusual halogen-lithium exchange with LTMP has been observed. A new synthetic route to Leshmaniacides using metalation and cross coupling reactions is described.

Metalation of diazines XVII Very hindered bases as new metalating agents, Improvement of regioselectivity for the metalation of 3-chloro-6-methoxypyridazine

Abstract The different factors governing the regioselectivity of the metalation of 3-chloro-6-methoxypyridazine with alkylamides were studied. Very hindered bases were used as new metalating agents and a very good regioselectivity was obtained.

Regioselective synthesis and metallation of tributylstannylfluoropyrazines. Application to the synthesis of some new fluorinated liquid crystals diazines. Part 34

Starting from fluoropyrazine, a general synthetic route including metallation and palladium-catalyzed cross-coupling reactions is described to access to rod-like alkylaryl or diarylpyrazines. Among them, some have liquid crystalline properties.

OLIGOMERS CONTAINING ETHYNYLPYRIDAZINE MOIETIES : SYNTHESIS, FLUORESCENCE AND LIQUID CRYSTALLINE PROPERTIES. DIAZINES 50

Conjugated oligomers with ethynylpyridazine units have been synthetized by Sonogashira and Suzuki cross-coupling reactions. Some of them present interesting liquid crystals properties investigated by differential scanning calorimetry (DSC) and polarized light microscopy. Some of these oligomers are fluorescent.

FUNCTIONALIZATION BY METALLATION OF FLUOROPYRAZINE. DIAZINES XXI

Abstract Lithiation of fluoropyrazine followed by quenching with various electrophiles was successfully achieved and was used to synthesize new pyrazine derivatives. A further lithiation of 2-fluoro-3-substituted pyrazines allowed access to 2,3,6-trisubstituted pyridazine derivatives. As an application, a one-pot synthesis of a quinuclidinylfluoropyrazine has been performed. When the 3-substituent bears a TMS protected alcohol, functionalization via metallation at C 5 position provides tetrasubstituted pyrazines in good yield.