Tuning of a Hydrogen-Bonded Organic Framework by Liquid-Assisted Mechanosynthesis between Trans-Aconitic Acid and Isonicotinamide.

Cocrystallization of trans-aconitic acid (TACA) and isonicotinamide (INA) using liquid assisted mechanochemical grinding results in a unique supramolecular hydrogen-bonded organic framework (HOF) system encapsulating various organic solvents (liquid guest) with the formation of channel inclusion compounds. Dimension and shape of the framework is dependent on the solvent used during liquid assisted grinding (LAG). Although crystal structure of the cocrystal (TACA) ⋅ (INA) ⋅ (HO)@(INA) has been determined by Single Crystal X-ray diffraction (SCXRD), crystal structures of 3 cocrystal HOFs were determined by microcrystal electron diffraction (MicroED) and synchrotron X-ray diffraction due to lack of suitable single crystal.

Bidirectional strain release in a thermosalient organic salt crystal induced by anisotropic thermal expansion and phase transformation.

The jumping of crystals in the presence of external stimuli such as temperature, light, and mechanical forces is observed due to the release of accumulated strain in the crystal. Thermosalience in molecular crystals is generally induced by anisotropic thermal expansion accompanied by phase transformation. However, a thermosalient effect has not been observed in the same crystal at two different temperature zones caused by two distinct mechanisms.

An acid-promoted substitution manifold of γ-aminocyclopentenone enables divergent access to polycyclic indole derivatives.

We demonstrated γ-aminocyclopentenones to be a suitable surrogate for reactive cyclopentadienone a -substitution manifold. This approach enabled its orchestrated annulation with "tailored" bis-nucleophiles and to furnish complex β,γ-annulated cyclopentanoids or indole-based polycyclic architectures. This strategy represents a generalized means for direct, regioselective and stereoselective β,γ-functionalization of monosubstituted or unsubstituted aminocyclopentenones.

Leveraging the Domino Skeletal Expansion of Thia-/Selenazolidinones via Nitrogen-Atom Transfer in Hexafluoroisopropanol: Room Temperature Access to Six-Membered S/Se,N-Heterocycles.

Herein, a highly regioselective domino skeletal-expansion process that transforms 2-aminothiazolidinone into six-membered S,N-heterocycle is developed with the aid of TMS-azide in hexafluoroisopropanol (HFIP) at ambient temperature. Functioning of the C2 tertiary amine as latent reactive group on thiazolidinone moiety was the key to this development, which allowed relay substitution with azide and imparted subsequent ring-expansion under metal/acid free-conditions. The reaction also underscored an intermolecular nitrogen-atom transfer process from TMS-azide leading to final products, where any intermediary azidothiazolidinone was absent.

Unprecedented Reactivity of γ-Amino Cyclopentenone Enables Diversity-Oriented Access to Functionalized Indoles and Indole-Annulated Ring Structures.

Observation of an unexpected, Lewis acid promoted displacement of latent reactive γ-amino group on cyclopentenone presented unparalleled opportunity for enone functionalization and annulations with indole derivatives, which is developed in the current study. Herein, a vast range of C3/N-indolyl enones and indole alkaloid-like compound were accessed in excellent yields (up to 99 %) and selectivity through a one-pot operation. The mechanism most likely involves an unprecedented trait of Piancatelli-type rearrangement where influence of the gem-diaryl group appeared crucial.

Multicomponent, Tandem 1,3- and 1,4-Bisarylation of Donor-Acceptor Cyclopropanes and Cyclobutanes with Electron-Rich Arenes and Hypervalent Arylbismuth Reagents.

A tandem catalytic process for 1,3- and 1,4-bisarylation of donor-acceptor (D-A) cyclopropanes and cyclobutanes is disclosed. This strategy capitalizes on the use of two distinct sources of nucleophilic and electrophilic arylating agents, affording the formation of two new C-C bonds in an orchestrated multicomponent fashion with the aid of a catalytic Lewis acid. Mechanistic investigations have revealed it to be a stereoselective process, and products could be easily elaborated into other useful compounds.

[3 + 2]-Annulation of Azaoxyallyl Cations and Thiocarbonyls for the Assembly of Thiazolidin-4-ones.

A base-promoted, efficient [3 + 2] annulation between azaoxyallyl cations and thiocarbonyls is reported for flexible access to highly functionalized thiazolidin-4-one derivatives in good to excellent yields. An intriguing feature of this method is the metal or Lewis acid free late-stage entry of distinct set of functional groups at C2 of thiazolidin-4-ones via substitution of a latent amino functional group. Overall, this approach constitutes a general platform for convenient access to this medicinally important scaffold.

Lewis acid catalyzed annulation of spirocyclic donor-acceptor cyclopropanes with exo-heterocyclic olefins: access to highly functionalized bis-spirocyclopentane oxindole frameworks.

Lewis acid catalyzed highly efficient [3+2] annulation of spirocyclic Donor-Acceptor cyclopropanes (DACs) with exo-heterocyclic olefins is reported to furnish various biologically relevant dispiro-2,3-dioxopyrrolidine[cyclopentane]oxindole and dispiropyrazolone[cyclopentane]oxindole frameworks. This report highlights the use of oxindole-activated spiro-DACs as potential synthons to access complex dispirocarbocyclic oxindoles via ring-enlargement of the former, with high yields and diastereoselectivity.

Lewis Acid Catalyzed Nucleophilic Ring Opening and 1,3-Bisfunctionalization of Donor-Acceptor Cyclopropanes with Hydroperoxides: Access to Highly Functionalized Peroxy/(α-Heteroatom Substituted)Peroxy Compounds.

The Lewis acid catalyzed ring opening reaction of Donor-Acceptor (D-A) cyclopropanes with alkyl hydroperoxides is reported to furnish various peroxycarbonyls and 1,3-haloperoxygenated compounds in good to excellent yields. This method adds another instance to scarcely reported noncyclilizing 1,3-bisfunctionalization of D-A cyclopropanes with two different functional groups and relies on the dual role of peroxide as nucleophile and oxidant through an orchestrated reaction sequence. The products obtained, including α-heterosubstituted peroxy compounds, are amenable to useful synthetic elaboration.

Polymorphism in some new bis-hydrazone compounds.

We describe the polymorphism of four new bis-hydrazone compounds, namely butane-2,3-dione 2,3-bis{[bis(4-fluorophenyl)methylidene]hydrazone}, CHFN (1), butane-2,3-dione 2,3-bis{[bis(4-chlorophenyl)methylidene]hydrazone}, CHClN (2), butane-2,3-dione 2,3-bis{[bis(4-methylphenyl)methylidene]hydrazone}, CHN (3), and butane-2,3-dione 2,3-bis({bis[4-(dimethylamino)phenyl]methylidene}hydrazone), CHN (4), derived by the condensation reaction between substituted benzophenone hydrazone and butane-2,3-dione. Concomitant polymorphism has been observed in 1, 2 and 3. Overlays of molecules of the different polymorphs indicate that there is conformational adjustment in the crystal structures of the polymorphs of 1 and 2, i.

Switching from positive to negative axial thermal expansion in two organic crystalline compounds with similar packing.

Switching from positive to negative axial thermal expansion in pure organic materials is reported for the first time. This rare phenomenon has been rationalized based on the packing of molecules in crystal structures and transverse thermal vibrations of atoms in the molecule. Unique packing of the molecules in the crystal structure contributes to the restricted movement of molecules along the c axis.

Organocatalytic, Asymmetric Synthesis of Aza-Quaternary Center of Izidine Alkaloids: Synthesis of (-)-Tricyclic Skeleton of Cylindricine.

We report a highly efficient, enantioselective, organocatalytic method for the synthesis of izidinone alkaloids containing a bridgehead aza-quaternary center using ketone-derived N,O-hemiaminal with a tethered acetal. Alkyl-, aryl-, and alkenyl-substituted substrates cyclize to the respective products with excellent enantioselectivities. Five- and seven-membered ring formation has also been established.

Anomalous thermal expansion of an organic crystal--implications for elucidating the mechanism of an enantiotropic phase transformation.

Two enantiotropic polymorphs of a dumbbell shaped molecule possess similar packing arrangements, in principle, but one of the polymorphs shows anomalously anisotropic thermal expansion while the other does not.

Reversible single-crystal to single-crystal polymorphic phase transformation of an organic crystal.

Two polymorphs of a substituted dihydroanthracene derivative were prepared by crystallization from different solvents. Each polymorph is reversibly interconvertible to the other by means of a single-crystal to single-crystal phase transformation.

Exceptionally large positive and negative anisotropic thermal expansion of an organic crystalline material.

In general, the relatively modest expansion experienced by most materials on heating is caused by increasing anharmonic vibrational amplitudes of the constituent atoms, ions or molecules. This phenomenon is called positive thermal expansion (PTE) and usually occurs along all three crystallographic axes. In very rare cases, structural peculiarities may give rise either to anomalously large PTE, or to negative thermal expansion (NTE, when lattice dimensions shrink with heating).

Concomitant formation of two different solvates of a hexa-host from a binary mixture of solvents.

Crystallization of hexakis(4-cyanophenyloxy)benzene from a mixture of two different solvents produces two different solvates concomitantly, which were characterized by X-ray diffraction, thermal analysis and NMR spectroscopy.

Polymorphism of a hexa-host: isolation of four different single-crystal phases by melt crystallization.

A hexa-host compound yields at least four polymorphic forms from its melt phase. All four phases have been characterized using single-crystal X-ray diffraction; two of the phases were obtained by means of thermal stress, and the different forms exhibit conformational polymorphism.

Methyl 4-(trimethyl-silylethyn-yl)benzoate.

The title compound, C(13)H(16)O(2)Si, was synthesized as a precursor for ethynylarene derivatives and crystallized from hexane. In the crystal structure, mol-ecules are linked by weak C-H⋯O hydrogen bonds to form chains that pack in layers in a herringbone fashion.

Packing modes in some mono- and disubstituted phenylpropiolic acids: repeated occurrence of the rare syn,anti catemer.

The catemer is an infinite one-dimensional pattern formed by the carboxylic acid group in crystals, and is constituted with O-H...

Synthon evolution and unit cell evolution during crystallisation. A study of symmetry-independent molecules (Z' > 1) in crystals of some hydroxy compounds.

A kinetically favoured crystal, with many molecules in the asymmetric unit, may be a fossil relic of the crystal nucleus of a more stable polymorph.