Gold(I)-Catalyzed Bis-Cyclization of Allenynes for the Synthesis of Strained and Planar Polycyclic Compounds

A gold-catalyzed cascade cyclization of naphthalene-tethered allenynes gave strained fused phenanthrene derivatives. The reaction proceeds through the nucleophilic reaction of an alkyne with the activated allene to generate a vinyl cation intermediate, followed by arylation with a tethered naphthalene ring to form the 4H-cyclopenta[def]phenanthrene (CPP) scaffold. When using aryl-substituted substrates on the alkyne terminus, the gold-catalyzed reaction produced dibenzofluorene derivatives along with the CPP derivatives. Selective formation of CPP and dibenzofluorene derivatives depending on the reaction conditions is also presented.     

Porous Mn2+ Magnet with a Pt−Cl Framework: Correlation between Water Vapor Adsorption/Desorption and Slow Magnetic Relaxation

We report the water adsorption/desorption behavior and dynamic magnetic properties of the Pt−Cl chain complex [{[Pt(en)₂][PtCl₂(en)₂]}₃][{(MnCl₅)Cl₃}₂] ⋅ 12H₂O ( 1 ). Upon heating 1 in a vacuum, we obtained the dehydrated form [{[Pt(en)₂][PtCl₂(en)₂]}₃][{(MnCl₅)Cl₃}₂] ( 1DH ). The framework structures of 1 and 1DH are identical, and both complexes underwent slow magnetic relaxation. However, the magnetic relaxation times for 1DH were shorter than those for 1 , meaning that the dynamic magnetic properties were controlled upon water vapor adsorption/desorption. From detailed analyses of the dynamic magnetic behavior, a phonon-bottleneck effect contributes to the magnetic relaxation processes. We discuss the mechanism for the changes in the magnetic relaxation processes upon dehydration in terms of the heat capacity and thermal conductivity.     

Formation and High Reactivity of the anti‐Dioxo Form of High‐Spin μ‐Oxodioxodiiron(IV) as the Active Species That Cleaves Strong C−H Bonds

Recently, it was shown that μ‐oxo‐μ‐peroxodiiron(III) is converted to high‐spin μ‐oxodioxodiiron(IV) through O?O bond scission. Herein, the formation and high reactivity of the anti‐dioxo form of high‐spin μ‐oxodioxodiiron(IV) as the active oxidant are demonstrated on the basis of resonance Raman and electronic‐absorption spectral changes, detailed kinetic studies, DFT calculations, activation parameters, kinetic isotope effects (KIE), and catalytic oxidation of alkanes. Decay of μ‐oxodioxodiiron(IV) was greatly accelerated on addition of substrate. The reactivity order of substrates is toluene<ethylbenzene≈cumene<trans‐β‐methylstyrene. The rate constants increased proportionally to the substrate concentration at low substrate concentration. At high substrate concentration, however, the rate constants converge to the same value regardless of the kind of substrate. This is explained by a two‐step mechanism in which anti‐μ‐oxodioxodiiron(IV) is formed by syn‐to‐anti transformation of the syn‐dioxo form and reacts with substrates as the oxidant. The anti‐dioxo form is 620 times more reactive in the C?H bond cleavage of ethylbenzene than the most reactive diiron system reported so far. The KIE for the reaction with toluene/[D₈]toluene is 95 at ?30 °C, which the largest in diiron systems reported so far. The present diiron complex efficiently catalyzes the oxidation of various alkanes with H₂O₂.     

Cationic polymerization of 1-phenyl-4-ethyl-2,6,7-trioxabicyclo[2.2.2]octane

Cationic polymerization of bicyclo ortho ester, 1-phenyl-4-ethyl-2,6,7-trioxabicyclo[2.2.2]octane, was carried out with Lewis acids and cation sources to obtain the polyether containing ester group in the side chain. It was found that boron trifluoride etherate was the most active initiator in the Lewis acids. Magnesium perchlorate and triphenylcarbenium tetrafluoroborate, which have lower nucleophilic counter ions, initiated effectively the polymerization of bicyclo ortho ester.     

Interval solution of nonlinear equations using linear programming

A new computational test is proposed for nonexistence of a solution to a system of nonlinear equations in a convex polyhedral regionX. The basic idea proposed here is to formulate a linear programming problem whose feasible region contains all solutions inX. Therefore, if the feasible region is empty (which can be easily checked by Phase I of the simplex method), then the system of nonlinear equations has no solution inX. The linear programming problem is formulated by surrounding the component nonlinear functions by rectangles using interval extensions. This test is much more powerful than the conventional test if the system of nonlinear equations consists of many linear terms and a relatively small number of nonlinear terms. By introducing the proposed test to interval analysis, all solutions of nonlinear equations can be found very efficently. This work was partially supported by the Japanese Ministry of Education.