Jean-Pierre Fleury

A NEW STRATEGY FOR THE SYNTHESIS OF BIFLAVONOIDS VIA ARYLBORONIC ACIDS

Abstract Amentoflavone derivatives were prepared by catalytic coupling of 8-flavone-boronic acids with iodoflavones. 3-Arylflavones, as biflavonoid synthon, are accessible by the method.

A new aspect of azo-hydrazone tautomerism

Abstract Structures of 3,5-dimethoxy-4-hydroxyazobenzene and of a new parent compound, 2,6-dimethoxy-4-hydroxyazobenzene, are investigated. Owing to their very high solubility it was possible to proceed to a comparison of the UV, 1 H NMR and 13 C NMR data for the same solvent. Symmetric substitution by two OMe groups in the ring bearing the OH group results in the isolation of the azo or hydrazone tautomer, using the available positions of substitution. The usefulness of the 13 C NMR technique in the investigation of azo-hydrazone tautomerism is underlined.

Mesoionic trifluoroacetylated 5-imino oxazolines: a re-examination of the structure using 13C NMR spectroscopy and cycloaddition reactions

Abstract The position of the trifluoroacetyl group in mesoionic 2,3-diaryl-5-imino oxazolines has been disputed. The natural abundance 13 C NMR spectra and the 1,3-dipolar cycloaddition product of the mesoionic oxazoline with the dimethylacetylenedicarboxylate are compatible with a structure in which the trifluoroacetyl group is bonded to the exocyclic 5-imino nitrogen.

A new route to trinuclear carbocyanines

Abstract Amides or vinylogous amides react with tosyl chloride-pyridine to form activated intermediates which condense with Fischers base or their vinylogs to give carbocyanine structures. Under the same conditions formylated Fischers base reacts with vinylogous Fischers bases to give trinuclear carbocyanines in good yields. Their structure and the limitations of this route are discussed.

Nouvelle voie d'acces au diethylacetal de l'amino-2 cyano-3 formyl-5 pyrazine

Abstract An unequivocal two step synthesis of 2-amino-3-cyano-5-formylpyrazine diethylacetal, starting from dimethylaminoacrolein and O-tosylisonitrosomalononitrile, is described. This pyrazine is a key intermediate for the preparation of folic acid and various analogues.