Monofluorinated Nitrogen Containing Heterocycles: Synthesis, Characterization and Fluorine Effect

A straight forward synthesis and efficient introduction of fluoromethyl group in nitrogen heterocycles is reported. Starting from the respective NH heterocycles fluoromethylation is performed with fluoroiodomethane and proceeds under mild reaction conditions. Structural information of monofluoromethylated nitrogen‐containing cyclic compounds containing the biologically active NCH2F moiety are reported. The particularly impressively change of physical and spectroscopic properties by the substitution of a methyl group by a monofluoromethyl group is discussed based on these examples

Reagents for Selective Fluoromethylation: A Challenge in Organofluorine Chemistry

The introduction of a monofluoromethyl moiety has undoubtedly become a very important area of research in recent years. Owing to the beneficial properties of organofluorine compounds, such as their metabolic stability, the incorporation of the CH2F group as a bioisosteric substitute for various functional groups is an attractive strategy for the discovery of new pharmaceuticals. Furthermore, the monofluoromethyl unit is also widely used in agrochemistry, in pharmaceutical chemistry, and in fine chemicals. The problems associated with climate change and the growing need for environmentally friendly industrial processes mean that alternatives to the frequently used CFC and HFBC fluoromethylating agents (CH2FCl and CH2FBr) are urgently needed and also required by the Montreal Protocol. This has recently prompted many researchers to develop alternative fluoromethylation agents. This Minireview summarizes both the classical and new generation of fluoromethylating agents. Reagents that act via electrophilic, nucleophilic, and radical pathways are discussed, in addition to their precursors

Halogen bonding in the crystal structures of 1,2-diiodo alkenes

Supramolecular templating techniques have been widely used to direct the formation of porous materials with the goal of introducing permanent mesoporosity. While surfactant-directed self-assembly has been exploited for inorganic materials such as titania, silica, organosilica, and zeolites, it has rarely been applied to metal-organic frameworks (MOFs) and coordination polymers. Here we introduce a new family of gemini surfactant-directed zinc imidazolates, referred to as mesostructured imidazolate frameworks (MIFs), and present a detailed study on the influence of different gemini-type surfactants on the formation mechanism and structures of the resulting zinc imidazolates. The proposed formation mechanism for MIF-type materials involves co-assembly and crystallization processes that yield lamellar mesostructured imidazolate frameworks. Understanding and controlling such processes also has implications for the syntheses of microporous zinc imidazolate framework (ZIF) materials, whose formation can be suppressed in surfactant-rich solutions, whereas formation of MIF materials is favored in the presence of surfactants and triggered by the addition of halogenides. Solid-state 2D 13C1H HETCOR NMR measurements on prototypic CTAB-directed MIF-1 establish that the head group moieties of the surfactant molecules interact strongly with the zinc-imidazolate-bromide sheets. Additionally, the NMR analyses suggest that MIF-1 has a significant fraction of surfactant molecules that are interdigitated between the zinc-imidazolate-bromide sheets with an antiparallel stacking arrangement, consistent with the high thermal and chemical stability of the MIF hybrid materials

Halogen bonding in the crystal structures of 1,2-diiodo alkenes

Supramolecular templating techniques have been widely used to direct the formation of porous materials with the goal of introducing permanent mesoporosity. While surfactant-directed self-assembly has been exploited for inorganic materials such as titania, silica, organosilica, and zeolites, it has rarely been applied to metal-organic frameworks (MOFs) and coordination polymers. Here we introduce a new family of gemini surfactant-directed zinc imidazolates, referred to as mesostructured imidazolate frameworks (MIFs), and present a detailed study on the influence of different gemini-type surfactants on the formation mechanism and structures of the resulting zinc imidazolates. The proposed formation mechanism for MIF-type materials involves co-assembly and crystallization processes that yield lamellar mesostructured imidazolate frameworks. Understanding and controlling such processes also has implications for the syntheses of microporous zinc imidazolate framework (ZIF) materials, whose formation can be suppressed in surfactant-rich solutions, whereas formation of MIF materials is favored in the presence of surfactants and triggered by the addition of halogenides. Solid-state 2D 13C1H HETCOR NMR measurements on prototypic CTAB-directed MIF-1 establish that the head group moieties of the surfactant molecules interact strongly with the zinc-imidazolate-bromide sheets. Additionally, the NMR analyses suggest that MIF-1 has a significant fraction of surfactant molecules that are interdigitated between the zinc-imidazolate-bromide sheets with an antiparallel stacking arrangement, consistent with the high thermal and chemical stability of the MIF hybrid materials

Spontaneous Reductive Elimination at Iridium(III) Induced by the Strong π‐Acceptor Ligand Trifluorophosphane

The reaction of the cyclometalated five‐coordinate 16 VE iridium(III) compound [IrCl(H)(P(tBu)2C6H4‐κ2P,C)(P(tBu)2Ph)] (1) with the strong π‐acceptor ligand trifluorophosphane resulted quickly in the quantitative formation of the new iridium(I) complex trans‐[IrCl(PF3)(P(tBu)2Ph)2] (2). This unexpected spontaneous reductive elimination was already observed in reactions of 1 with the very strong π‐acceptor ligands CO and NO+. First indications during reactions of 1 with lesser strong π‐acceptor ligands like alkyl or arylphosphanes did not show this inversion behavior of the cyclometalation. The title species 2 was characterized by spectroscopic methods and its molecular structure in the crystal was confirmed by X‐ray crystallography

Improved Preparation of 3-Oximinooxetane - An Important Precursor to Energetic Oxetanes

Oximes represent an extremely versatile building block in energetic materials chemistry. While oxidation with peroxy acids affords the corresponding mononitro compounds, tandem oxidation-nitration reactions such as the Scholl reaction lead to geminal dinitro compounds. Furthermore, the corresponding amines can be obtained by reduction of the oxime group. Accordingly, 3-oximinooxetane represents a suitable precursor for 3-nitro- and 3,3-dinitrooxetane as well as 3-aminooxetane. 3-Oximinooxetane, which is poorly described in the literature, has now been extensively characterized by vibrational-, mass- and NMR spectroscopy, as well as elemental and thermal analysis. In addition, its synthesis has been significantly improved compared to literature. The molecular structure was elucidated by single-crystal X-ray diffraction. Since 3-oximinooxetane is energetic by itself, its performance was calculated using the EXPLO5 V6.04 thermochemical code, and its sensitivity towards external stimuli such as impact, friction, and electrostatic discharge was determined by BAM standard procedures

Oxetane Monomers Based On the Powerful Explosive LLM-116: Improved Performance, Insensitivity, and Thermostability

3-Bromomethyl-3-hydroxymethyloxetane represents an inexpensive and versatile precursor for the synthesis of 3,3-disubstituted oxetane derivatives. In the present work, its synthesis was improved and energetic oxetanes based on the explosive LLM-116 (4-amino-3,5-dinitro-1H-pyrazole) prepared. Reaching detonation velocities and pressures of up to 7335 ms(-1) and 20.9 GPa in combination with a high thermostability and insensitivity, these surpass the prior art by far. Next to a symmetric LLM-116 derivative, three asymmetric compounds were prepared using azido-, nitrato- and tetrazolyl-moieties. All compounds were intensively characterized by vibrational-, mass- and multinuclear (H-1, C-13, N-14) NMR spectroscopy, differential scanning calorimetry and elemental analysis. The molecular structures were elucidated by single crystal X-ray diffraction. Hirshfeld analysis allowed to estimate their sensitivity next to a practical evaluation using BAM standard procedures. Their performance was calculated using the EXPLO5 V6.04 code and a small-scale shock reactivity test and initiation test demonstrated their insensitivity and performance

Iron-Catalyzed Radical Zincations of Alkyl Iodides

We report a new iron-catalyzed I/Zn-exchange allowing to convert primary or tailored secondary alkyl iodides into the corresponding alkylzinc iodides. In the presence of a remote double bond at position 5, diastereoselective ring closures are observed. Quenching of these zinc reagents, after transmetalation to copper species (with CuCN center dot 2LiCl) or under Pd-catalysis, with typical electrophiles (allyl bromides, acid chlorides or aryl iodides) gave various polyfunctional products

Continuous Flow Preparation of Benzylic Sodium Organometallics

We report a lateral sodiation of alkyl(hetero)arenes using on-demand generated hexane-soluble (2-ethylhexyl)sodium (1) in the presence of TMEDA. (2-Ethylhexyl)sodium (1) is prepared via a sodium packed-bed reactor and used for metalations at ambient temperature in batch as well as in continuous flow. The resulting benzylic sodium species are subsequently trapped with various electrophiles including carbonyl compounds, epoxides, oxetane, allyl/benzyl chlorides, alkyl halides and alkyl tosylates. Wurtz-type couplings with secondary alkyl halides and tosylates proceed under complete inversion of stereochemistry. Furthermore, the utility of this lateral sodiation is demonstrated in the synthesis of pharmaceutical relevant compounds. Thus, fingolimod is prepared from p-xylene applying the lateral sodiation twice. In addition, 7-fold isotopically labeled salmeterol-d(7) and fenpiprane as well as precursors to super linear alkylbenzene (SLAB) surfactants are prepared

Nitrogen-Rich Oxetanes Based on the Combination of Azides and Tetrazoles

Literature known energetic oxetane derivatives have a nitrogen content of up to 49.98 %. Through the introduction of azide and tetrazole functionalities attached to an oxetane ring, energetic oxetanes with higher nitrogen contents than previously reported in the literature were obtained. The newly synthesized oxetane derivatives were extensively characterized via H-1 NMR, C-13{H-1} NMR, N-14 NMR, N-15 NMR, H-1-N-15 HMBC, FT-IR spectroscopy and/or DTA. Their crystal structures were elucidated using X-ray diffraction, their sensitivities towards impact, friction and electrostatic discharge were determined and their energetic properties were calculated using the EXPLO5 code