Total Synthesis of Lajollamycin B

The first total synthesis of lajollamycin B, a structurally novel nitro-tetraene spiro-β-lactone/γ-lactone antibiotic, is described. The convergent synthesis involves the construction of the C8′–C11′ nitrodienylstannane and its coupling with the segment prepared from the C1′–C7′ ω-iodoheptadienoic acid and the right-hand heterocyclic fragment, which has been utilized for our previous syntheses of oxazolomycin A. The revision of the geometry of the terminal Δ^{10′, 11′}-double bond from E to Z is also described for the structure of natural lajollamycin B.     

Ferroelectric Coordination Polymers Self‐Assembled from Mesogenic Zinc(II) Porphyrin and Dipolar Bridging Ligands

A new class of ferroelectric coordination‐based polymers has been developed by the self‐assembly of lipophilic zinc porphyrin ( ZnP ) and ditopic bridging ligands. The ligands contain dipolar benzothiadiazole or fluorobenzene units, which are axially coordinated to ZnP with the dipole moments oriented perpendicular to the coordination axes. The coordination‐based polymers show ferroelectric characteristics in the liquid crystalline state, as revealed by distinctive hysteresis in the polarization–electric field (P–E) loops and inversion current peaks in current–voltage (I–V) loops. The observed ferroelectric properties are explainable by flip–flop rotation of the dipolar axle ligands induced by the applied electric field, as demonstrated by the positive‐up–negative‐down (PUND) measurements. The present system provides a new operating principle in supramolecular ferroelectrics.     

Synthesis and Chiroptical Properties of Chiral Carbazole-Based BODIPYs

A series of carbazole-based boron dipyrromethenes (BODIPYs) 2 a – g bearing binaphthyl units have been synthesized by the Et₂AlCl-mediated reaction of the corresponding BODIPY difluorides 1 a – g with 1,1′-binaphthalene-2,2′-diol. Substituents such as halogen, nitrile, and amino groups were tolerated under the reaction conditions, and the reaction of the phenylethynyl-substituted 1 h gave (R,R)- 3 h bearing two binaphthyl units. The chiroptical properties of these dyes with different substituents were investigated by UV/Vis, CD, fluorescence, and circularly polarized luminescence (CPL) spectroscopy. The CD spectra showed Cotton effects in the absorption region of the BODIPY moieties. In addition, they showed CPL both in solution and in the solid state. Interestingly, several dyes recorded higher g_lum values in the solid state, probably due to intermolecular interactions. Because (R,R)- 3 h recorded relatively low g_lum values, the diastereomer (R,S)- 3 h was prepared. The (R,S) diastereomer showed intense CPL, which suggests a synergetic effect of the two binaphthyl groups. Finally, chiral carbazole-based BODIPY dimers have been synthesized for the first time and their chiroptical properties were investigated. They showed redshifted fluorescence and CPL, which reached the near-IR (NIR) region in the solid state.     

Catalytic Activity of Molybdenum Complexes Bearing PNP-Type Pincer Ligand toward Ammonia Formation

We newly designed and prepared a novel molybdenum complex bearing a 4-[3,5-bis(trifluoromethyl)phenyl]pyridine-based PNP-type pincer ligand, based on the bond dissociation free energies (BDFEs) of the N−H bonds in molybdenum-imide complexes bearing various substituted pyridine-based PNP-type pincer ligands. The complex worked as an excellent catalyst toward ammonia formation from the reaction of an atmospheric pressure of dinitrogen with samarium diiodide as a reductant and water as a proton source under ambient reaction conditions, where up to 3580 equivalents of ammonia were formed based on the molybdenum atom of the catalyst. The catalytic activity was significantly improved by one order of magnitude larger than that observed when using the complex before modification.     

Some Observations on the Impact of a Low-Solubility Ionic Solution on Drying Characteristics of a Model Porous Medium

Transport in Porous Media - We study the impact, on the drying rate, of the presence of suspended elements, such as calcium sulfate ions, in the interstitial fluid of a porous medium. In order to...     

Monte carlo simulations for blue-phase structure in liquid crystals

Blue-phase liquid crystals form three-dimensional structures in a self-organizing manner and are similar to living tissue structures such as the teeth of mice and collagen tissues. This study presents numerical results regarding the conditions under which blue-phase liquid crystals occur. The Monte Carlo simulations are performed by employing an improved Lennard–Jones potential that considers anisotropy and chirality. The conditions for the formation of the blue phase, which vary with respect to the chirality, are examined first. The relationship between the anisotropic parameters and the chiral parameter for the formation of the blue phase is discussed. Identical blue-phase structures are obtained, even when the cell size and molecular number are varied drastically. This discussion is useful for considering the scale-up problem, which is almost always a difficult issue for molecular-scale simulations.     

Efficient Synthesis of Polycyclic γ-Lactams by Catalytic Carbonylation of Ene-Imines via Nickelacycle Intermediates

The nickel(0)-catalyzed carbonylative cycloaddition of 1,5- and 1,6-ene-imines with carbon monoxide (CO) is reported. Key to this reaction is the efficient regeneration of the catalytically active nickel(0) species from nickel carbonyl complexes such as [Ni(CO)₃L]. A variety of tri- and tetracyclic γ-lactams were thus prepared in excellent yields with 100 % atom efficiency. Preliminary results on asymmetric derivatives promise potential in the synthesis of enantioenriched polycyclic γ-lactams.