Crystalline tetrazepam as a case study on the volume change on melting of molecular organic compounds

The volume change on melting is a rarely studied quantity and it is not well understood even if it must reflect the changes in interaction between the solid and the liquid state. It is part of the solid-state information for materials and pharmaceuticals and it is important for the reliability of polymorph stability study results. Using the crystal structure of monoclinic tetrazepam at 150 K and at room temperature, in addition to powder X-ray diffraction as a function of the temperature, the specific volume of tetrazepam has been determined over a large temperature domain. In combination with a pressure-temperature curve for the melting of tetrazepam, its volume change on melting could be determined. With this information and previous data from the literature, the assumption that the volume of the solid increases on average with 11% on melting has been investigated. It can be concluded that this value is not constant; however so far, no simple relationship has been found to relate the solid state to its volume change on melting and using 11% remains best practice. A comparison of the tetrazepam crystal structure with diazepam and nordiazepam has been provided too.Peer ReviewedPostprint (author's final draft

Solid-State Characterization of Enantiomeric and Racemic Hydrated and Anhydrous Zinc-Pidolate Complexes

Zn(II) L- and DL-pidolates diaqua complexes dehydrate at around 407 K, leading to amorphous anhydrous complexes. Only amorphous anhydrous Zn(II) L-pidolate was found to crystallize on heating into a crystalline anhydrous phase whose crystal structure was solved from a high-resolution X-ray powder diffraction pattern. Orthorhombic anhydrous Zn(II) L-pidolate exhibits a structure in which (4 + 2)-coordinated Zn atoms (with four usual and two additional Zn-O distances of 2.53 and 2.69 Å) and L-pidolate ligands alternate so as to form a three-dimensional polymerized network. Room-temperature rehydration processes under saturating water vapor for amorphous and crystalline anhydrous complexes were found to be different from each other, although they all led back to crystalline diaqua complexes whose relative stabilities were inferred from measurements of their solubilities in water

On the Dimorphism and the Pressure-Temperature State Diagram of Gestodene, a Steroidal Progestogen Contraceptive

International audienc

2-Trimethylsilylethanesulfonyl (SES) versus Tosyl (Ts) Protecting Group in the Preparation of Nitrogen-Containing Five-Membered Rings. A Novel Route for the Synthesis of Substituted Pyrrolines and Pyrrolidines

International audienc

Characterization of molecular associations involving L-ornithine and α-ketoglutaric acid: crystal structure of L-ornithinium α-ketoglutarate

The crystal structure of L-ornithinium α-ketoglutarate (C5H13N2O2, C5H5O5) has been solved by direct methods using single crystal X-ray diffraction data. It crystallizes in the monoclinic system, space group P21, unit cell parameters a=15.4326(3), b=5.2015(1), c=16.2067(3) Å and β=91.986(1)°, containing two independent pairs of molecular ions in the asymmetric unit. An extensive hydrogen-bond network and electrostatic charges due to proton transfer provide an important part of the cohesive energy of the crystal. The conformational versatility of L-ornithine and α-ketoglutaric acid is illustrated by the present results and crystal structures available from the Cambridge Structural Database.La structure cristalline de l’α-cétoglutarate de L-ornithinium (C5H13N2O2, C5H5O5) a été resolue par les méthodes directes en utilisant les intensités du rayonnement X diffracté par un monocristal. Ce composé cristallise dans le système monoclinique, groupe d’espace P21. La maille élémentaire, de paramètres a = 15,4326(3), b = 5,2015(1), c = 16,2067(3) Å et β = 91.986(1)°, montre deux paires indépendantes d’ions moléculaires dans son unité asymétrique. L’énergie de cohésion du cristal résulte principalement du réseau tridimensionnel de liaisons hydrogène et des charges électrostatiques créées par transfert de protons. L’adaptabilité conformationnelle de la l-ornithine et celle de l’acide α-cétoglutarique sont illustrées par les résultats de la présente étude et par ceux extraits des structures cristallines disponibles dans la base de données structurales de Cambridg

An Efficient Synthesis of New 7-Trifluoromethyl-2,5-disubstituted Pyrazolo 1,5-a pyrimidines

International audienceA novel two-step synthesis of trifluoromethylated 3,5-disubstituted pyrazolo[1,5- a ]pyrimidines is reported from 3-aminopyrazoles and ethyl 4,4,4-trifluorobut-2-ynoate. The synthetic route begins with the one-pot synthesis of 7-trifluoromethylated pyrazolo[1,5- a ]pyrimidin-5-ones by condensation of 3-aminopyrazoles with a fluorinated alkyne. The products obtained are used as building blocks to synthesize directly, with excellent yields via C-O bond activation, a library of new fluorinated 3,5-disubstituted pyrazolo[1,5- a ]pyrimidines of biological interest. This operation efficiently allows C-C, C-N and C-S bond formation