Substitution Effect on Crystal Packings of Iodobenzonitriles and Iodophenols

The influence of iodine on the crystal packing of iodo-substituted benzonitriles (2−4) and phenols (5−7) was studied. To analyze the substituent effect, the series was completed, and the crystal structures of iodobenzene (1), m-iodobenzonitrile (3), m-iodophenol (6), and p-iodophenol (7) were determined. Ab initio density functional calculation methods were used to examine the energetic situation and dipole moments of the single molecules in all species

Selective Formation of Functionalized Disiloxanes from Terphenylfluorosilanes

The reactivity of the sterically hindered organofluorosilane 2,6-Mes2C6H3-SiF3 (1) (Mes = 2,4,6-trimethylphenyl) under hydrolytic conditions differs substantially from that of the corresponding organo chlorosilane. During the hydrolysis of 1 the combination of thermodynamic (increased Si−F bond strengths compared to Si−Cl) and kinetic aspects (steric hindrance) favors condensation of intermediately formed silanol over the hydrolysis to give a silanetriol. In the course of the reaction no evidence for a silanetriol could be found, while the corresponding difluorosilanol seems to be a key intermediate. The condensation of this difluorosilanol leads to a tetrafluorodisiloxane, which can be isolated. Further displacement of the remaining fluorine atoms in this siloxane is possible with organolithium reagents or base. In the latter case the deprotonated disiloxanetetrol is formed, which due to its fourfold silanol functionality is a suitable precursor for metallasiloxanes. The deprotonated disiloxanetetrol forms a dimeric structure in the solid state, which is stabilized by hydrogen bonding and potassium aryl interaction

Fluorobenzonitriles: Influence of the Substitution Pattern on Melting and Crystallization Properties

The influence of the substitution pattern on the crystal packing of mono-fluorine-substituted benzonitriles was investigated by DSC measurements and crystal structure determination. The low melting compounds ortho-fluorobenzonitrile and meta-fluorobenzonitrile were crystallized by in situ crystallization directly on the diffractometer

Fluorobenzonitriles: Influence of the Substitution Pattern on Melting and Crystallization Properties

The influence of the substitution pattern on the crystal packing of mono-fluorine-substituted benzonitriles was investigated by DSC measurements and crystal structure determination. The low melting compounds ortho-fluorobenzonitrile and meta-fluorobenzonitrile were crystallized by in situ crystallization directly on the diffractometer

Selective Formation of Functionalized Disiloxanes from Terphenylfluorosilanes

The reactivity of the sterically hindered organofluorosilane 2,6-Mes2C6H3-SiF3 (1) (Mes = 2,4,6-trimethylphenyl) under hydrolytic conditions differs substantially from that of the corresponding organo chlorosilane. During the hydrolysis of 1 the combination of thermodynamic (increased Si−F bond strengths compared to Si−Cl) and kinetic aspects (steric hindrance) favors condensation of intermediately formed silanol over the hydrolysis to give a silanetriol. In the course of the reaction no evidence for a silanetriol could be found, while the corresponding difluorosilanol seems to be a key intermediate. The condensation of this difluorosilanol leads to a tetrafluorodisiloxane, which can be isolated. Further displacement of the remaining fluorine atoms in this siloxane is possible with organolithium reagents or base. In the latter case the deprotonated disiloxanetetrol is formed, which due to its fourfold silanol functionality is a suitable precursor for metallasiloxanes. The deprotonated disiloxanetetrol forms a dimeric structure in the solid state, which is stabilized by hydrogen bonding and potassium aryl interaction

Fluorobenzonitriles: Influence of the Substitution Pattern on Melting and Crystallization Properties

The influence of the substitution pattern on the crystal packing of mono-fluorine-substituted benzonitriles was investigated by DSC measurements and crystal structure determination. The low melting compounds ortho-fluorobenzonitrile and meta-fluorobenzonitrile were crystallized by in situ crystallization directly on the diffractometer

Self-Addition of a Sterically Hindered Alkynylselenolate

The unprecedented formation of a complex macrocyclic selenium−carbon ring system, which is initiated by the action of coordinating reagents upon a sterically hindered alkynylselenolate, has been observed. The crystal structure of the product could be obtained and shows a rigid tricyclic arrangement consisting only of selenium and sp2-hybridized carbon atoms. This reactivity stands in contrast to the corresponding unsubstituted alkynylselenolates and is an example where a bulky substituent destabilizes an adjacent unsaturated π-system

GABA-Controlled Synthesis of the Metastable Polymorphic Form and Crystallization Behavior with a Chiral Malic Acid

The controlled pH-based crystallization approach with acetic acid to the pharmaceutical interesting metastable polymorph II of the API γ-aminobutyric acid (GABA), which is hitherto accessible by sublimation under reduced pressure and high temperature, is described. Furthermore, the synthesis and single crystal characterization of a nonhydrated chiral [GABA-H]­[malate] compound is presented

Labeling of Peptides with Halocarbonyltungsten Complexes Containing Functional η²-Alkynyl Ligands

Two different seven-coordinate iodocarbonyltungsten complexes incorporating tris(pyrazolyl)borate ligands and η2-coordinated functionalized alkynes have been synthesized and characterized. [Tp*WI(CO)(η2-HCC(CH2)2CO2H)] (1), which has been characterized in the solid state by X-ray diffraction, was readily coupled to the hexa- and pentapeptides pseudo-neurotensin(8-13) and enkephalin in solid phase peptide synthesis (SPPS) to provide the N-terminal-labeled bioconjugates [Tp*WI(CO)(η2-HCC(CH2)2CO-NH-Lys-Lys-Pro-Tyr-Ile-Leu-OH)] (3) and [Tp*WI(CO)(η2-HCC(CH2)2CO-NH-Tyr-Gly-Gly-Phe-Leu-OH)] (4), respectively. [Tp*WI(CO)(η2-Fmoc-Pgl-OH)] (2, Pgl = propargylglycine) was utilized to synthesize the side-chain-labeled enkephalin derivative H2N-Tyr-Gly-[Tp*W(I)(CO)(η2-Pgl)]-Phe-Leu-OH (5). All new bioconjugates were comprehensively charaterized by HPLC, mass spectrometry, and multinuclear 1D and 2D spectroscopy. Their characteristic metal carbonyl IR band just over 1900 cm−1 and good stability against air and water make these Tp*W alkyne complexes valuable labels for biomolecules

Crystal Engineering under Hydrothermal Conditions: Cocrystals and Reactions of 3‑Cyanopyridine with Glutaric Acid

Crystallization under hydrothermal conditions is an interesting method to selectively influence crystallization pathways and processes. Crystallization of 3-cyanopyridine and glutaric acid from aqueous solutions under ambient conditions leads to the 2:1 cocrystalline entity 1 of 3-cyanopyridine and glutaric acid. Crystallizations under thermal and hydrothermal conditions lead, depending on the amounts of water used, to both the polymorphic forms 1 and 2 of the 2:1 cocrystalline entity of 3-cyanopyridine and glutaric acid and furthermore to the cocrystalline entity nicotinamide and glutaric acid