Nickel Catalyzed Cross-Coupling of Aryl C–O Based Electrophiles with Aryl Neopentylglycolboronates

The efficiency of mesylates, sulfamates, esters, carbonates, carbamates, and methyl ethers as C–O-based electrophiles attached to the 1- or 2-position of naphthalene and to activated and nonactivated phenyl substrates was compared for the first time in Ni-catalyzed cross-coupling with phenyl neopentylglycolboronates containing electron-rich and electron-deficient substituents in their <i>para</i>-position. These experiments were performed in the presence of four different Ni­(II)- and Ni(0)-based catalysts. Ni­(II)-based catalysts mediate the cross-coupling of most 2-naphthyl C–O electrophiles with both arylboronic acids and with neopentylglycolboronates when K₃PO₄ is used as base. The same catalysts are not efficient when CsF is used as base. However, Ni(0)-based catalysts exhibit selective efficiency, and when reactive, their efficiency is higher than that of Ni­(II)-based catalysts in the presence of both K₃PO₄ and CsF. These results provide both reaction conditions for the cross-coupling, and for the elaboration of orthogonal cross-coupling methodologies of various C–O based electrophiles with aryl neopentylglycolboronates. With the exception of mesylates and sulfamates the efficiency of all other 2-naphthyl C–O electrophiles was lower in cross-coupling with aryl neopentylglycolboronates than with arylboronic acid

Self-Organizable Vesicular Columns Assembled from Polymers Dendronized with Semifluorinated Janus Dendrimers Act As Reverse Thermal Actuators

The synthesis and structural analysis of polymers dendronized with self-assembling Janus dendrimers containing one fluorinated and one hydrogenated dendrons are reported. Janus dendrimers were attached to the polymer backbone both from the hydrogenated and from the fluorinated parts of the Janus dendrimer. Structural analysis of these dendronized polymers and of their precursors by a combination of differential scanning calorimetry, X-ray diffraction experiments on powder and oriented fibers, and electron density maps have demonstrated that in both cases the dendronized polymer consists of a vesicular columnar structure containing fluorinated alkyl groups on its periphery. This vesicular columnar structure is generated by a mechanism that involves the intramolecular assembly of the Janus dendrimers into tapered dendrons followed by the intramolecular self-assembly of the resulting dendronized polymer in a vesicular column. By contrast with conventional polymers dendronized with self-assembling tapered dendrons this new class of dendronized polymers acts as thermal actuators that decrease the length of the supramolecular column when the temperature is increased and therefore, are called reverse thermal actuators. A mechanism for this reversed process was proposed

TBAI/TBHP-Mediated Cascade Cyclization toward Sulfonylated Indeno[1,2‑<i>c</i>]quinolines

Treatment of <i>ortho</i>-amino-substituted aryldiyne derivatives with sulfonyl hydrazides in the presence of tetrabutylammonium iodide (TBAI) and <i>tert</i>-butyl hydroperoxide (TBHP) led to a cascade cyclization reaction to yield sulfonylated indeno­[1,2-<i>c</i>]­quinolines in moderate to good yields. The features of the methodology include metal-free reaction, the ease of reagent handling, and a broad functional group tolerance

<i>trans</i>-Chloro(1-Naphthyl)bis(triphenylphosphine)nickel(II)/PCy₃ Catalyzed Cross-Coupling of Aryl and Heteroaryl Neopentylglycolboronates with Aryl and Heteroaryl Mesylates and Sulfamates at Room Temperature

<i>trans</i>-Chloro­(1-naphthyl)­bis­(triphenylphosphine)­nickel­(II) complex/PCy₃ system has been successfully applied as catalyst for the Suzuki–Miyaura cross-coupling of aryl and heteroaryl neopentylglycolboronates with aryl and heteroaryl mesylates and sulfamates in THF at room temperature. This cross-coupling reaction tolerates various functional groups, including keto, imino, ester, ether, and cyano. Together with the nickel-catalyzed, one-pot, two-step neopentylglycolborylation, this bench stable and inexpensive Ni­(II)-based catalyst can be utilized as an alternative to Ni­(COD)₂<i>/</i>PCy₃ to provide an inexpensive, robust, and convenient synthesis of biaryl and heterobiaryl compounds

Air-Stable Nickel Precatalysts for Fast and Quantitative Cross-Coupling of Aryl Sulfamates with Aryl Neopentylglycolboronates at Room Temperature

A library containing 10 air-stable Ni^IIX­(Aryl)­(PCy₃)₂ σ-complexes as precatalysts (X = Cl, Br, OTs, OMs, aryl = 1-naphthyl, 2-naphthyl; X = Cl, 1-acenaphthenyl, 1-(2-methoxynaphthyl), 9-phenanthrenyl, 9-anthracyl) was synthesized and demonstrated to quantitatively cross-couple 2-methoxyphenyl dimethylsulfamate with methyl 4-(5,5-dimethyl-1,3,2-dioxaborinane-2-yl)­benzoate at 23 °C in dry THF in the presence of K₃PO₄(H₂O)_3.2 in less than 60 min. Lower or higher amounts of H₂O in K₃PO₄ and as received THF mediate the same transformation in a maximum three times longer reaction time

Transformation from Kinetically into Thermodynamically Controlled Self-Organization of Complex Helical Columns with 3D Periodicity Assembled from Dendronized Perylene Bisimides

The dendronized perylene 3,4:9,10-tetracarboxylic acid bisimide (PBI), (3,4,5)­12G1-1-PBI, was reported by our laboratory to self-assemble into complex helical columns containing dimers of dendronized PBI with one molecule in each stratum, with different intra- and interdimer rotation angles but identical intra- and interdimer distance of 3.5 Å, exhibiting a four-strata 2₁ helical repeat. A thermodynamically controlled 2D columnar hexagonal phase with short-range intracolumnar order represents the thermodynamic product at high temperature, while a kinetically controlled monoclinic columnar array with 3D periodicity is the thermodynamic product at low temperature. With heating and cooling rates higher than 10 °C/min to 1 °C/min, at low temperature the 2D columnar periodic array is the kinetic product for this dendronized PBI. Here the synthesis and structural analysis of a library of (3,4,5)<i>n</i>G1-<i>m</i>-PBI with <i>n</i> = 12 to 6 and <i>m</i> = 1 are reported. A combination of differential scanning calorimetry, X-ray diffraction on powder and orientated fibers, including pattern simulation and electron density map reconstruction, and solid-state NMR, all as a function of temperature and heating and cooling rate, was employed for their structural analysis. It was discovered that at low temperature the as-prepared <i>n</i> = 12 to 10 exhibit a 3D layered array that transforms irreversibly into columnar periodicities during heating and cooling. Also the kinetically controlled 3D columnar phase of <i>n</i> = 12 becomes thermodynamically controlled for <i>n</i> = 10, 9, 8, 7, and 6. This unprecedented transformation is expected to facilitate the design of functions from dendronized PBI and other self-assembling building blocks

Columnar Liquid Crystals in Cylindrical Nanoconfinement

Axial orientation of discotic columnar liquid crystals in nanopores of inorganic templates, with the columns parallel to the axis of the nanochannels, is considered desirable for applications such as production of molecular wires. Here, we evaluate experimentally the role of the rigidity of the LC columns in achieving such orientation in nanopores where the planar anchoring (<i>i.e.</i>, columns parallel to wall surface) is enforced. We studied the columnar phase of several discotic compounds with increasing column rigidity in the following order: dendronized carbazole, hexakis(hexyloxy)triphenylene (HAT6), a 1:1 HAT6-trinitrofluorenone (TNF) complex, and a helicene derivative. Using 2-D X-ray diffraction, AFM, grazing incidence diffraction, and polarized microscopy, we observed that the orientation of the columns changes from circular concentric to axial with increasing column rigidity. Additionally, when the rigidity is borderline, increasing pore diameter can change the configuration from axial back to circular. We derive expressions for distortion free energy that suggest that the orientation is determined by the competition between, on the one hand, the distortion energy of the 2-d lattice and the mismatch of its crystallographic facets with the curved pore wall in the axial orientation and, on the other hand, the bend energy of the columns in the circular configuration. Furthermore, the highly detailed AFM images of the core of the disclinations of strength +1 and +1/2 in the center of the pore reveal that the columns spiral down to the very center of the disclination and that there is no amorphous or misaligned region at the core, as suggested previously

Comparison of the A-T rich regions and the Bacillus subtilis RNA polymerase binding sites in phage ø29

By using a modification of the BAC spreading method for mounting the DNA for electron microscopy, partial denaturation maps of protein-free ø29 DNA and of ø29 DNA containing protein p3 were obtained. In ø29 P3-DNA1 the protein does not seem to influence the melting of the ends of the molecules. The comparison of the partial denaturation map and the B. subtilis RNA polymerase binding sites indicates that five of the seven early promoters (Al, A2, A3, B2 and C2) are located in A-T rich DNA regions whereas the other two early promoters (Bl and Cl) are located in less A-T rich sites.Peer reviewe

Complex Columnar Hexagonal Polymorphism in Supramolecular Assemblies of a Semifluorinated Electron-Accepting Naphthalene Bisimide

Simple synthetic methods for a strongly electron-accepting naphthalene bisimide (NBI) derivative functionalized with a new environmentally friendly chiral racemic semifluorinated alkyl group and with AB₃ minidendrons containing the same semifluorinated group are reported. The semifluorinated dendron was attached to the imide groups of the NBI via one, two, and three (<i>m</i> = 1, 2, 3) methylenic units. The NBI-containing semifluorinated groups and the dendronized NBI with <i>m</i> = 1 and 2 self-organize into lamellar crystals. The dendronized NBI with <i>m</i> = 3 self-assembles into an unprecedentedly complex and ordered column that self-organizes in a columnar hexagonal periodic array. This array undergoes a continuous transition to a columnar hexagonal superlattice that does not display a first-order phase transition during analysis by differential scanning calorimetry at heating and cooling rates of 10 and 1 °C/min. These complex columnar hexagonal periodic arrays with intramolecular order could be elucidated only by a combination of powder and fiber X-ray diffraction studies and solid-state NMR experiments. The lamellar crystals self-organized from <i>m</i> = 1 and the two highly ordered columnar hexagonal periodic arrays of <i>m</i> = 3 are assembled via thermodynamically controlled processes. Since strongly electron-accepting derivatives are of great interest to replace fullerene acceptors in organic photovoltaics and for other supramolecular electronic materials, the multitechnique structural analysis methodology elaborated here must be taken into consideration in all related studies

Screening Libraries of Semifluorinated Arylene Bisimides to Discover and Predict Thermodynamically Controlled Helical Crystallization

Synthesis, structural, and retrostructural analysis of a library containing 16 self-assembling perylene (PBI), 1,6,7,12-tetrachloroperylene (Cl₄PBI), naphthalene (NBI), and pyromellitic (PMBI) bisimides functionalized with environmentally friendly AB₃ chiral racemic semifluorinated minidendrons at their imide groups via <i>m</i> = 0, 1, 2, and 3 methylene units is reported. These semifluorinated compounds melt at lower temperatures than homologous hydrogenated compounds, permitting screening of all their thermotropic phases via structural analysis to discover thermodynamically controlled helical crystallization from propeller-like, cogwheel, and tilted molecules as well as lamellar-like structures. Thermodynamically controlled helical crystallization was discovered for propeller-like PBI, Cl₄PBI and NBI with <i>m</i> = 0. Unexpectedly, assemblies of twisted Cl₄PBIs exhibit higher order than those of planar PBIs. PBI with <i>m</i> = 1, 2, and 3 form a thermodynamically controlled columnar hexagonal 2D lattice of tilted helical columns with intracolumnar order. PBI and Cl₄PBI with <i>m</i> = 1 crystallize via a recently discovered helical cogwheel mechanism, while NBI and PMBI with <i>m</i> = 1 form tilted helical columns. PBI, NBI and PMBI with <i>m</i> = 2 generate lamellar-like structures. 3D and 2D assemblies of PBI with <i>m</i> = 1, 2, and 3, NBI with <i>m</i> = 1 and PMBI with <i>m</i> = 2 exhibit 3.4 Å π–π stacking. The library approach applied here and in previous work enabled the discovery of six assemblies which self-organize via thermodynamic control into 3D and 2D periodic arrays, and provides molecular principles to predict the supramolecular structure of electronically active components