Hiroyuki Yamamoto

Novel synthesis, static and dynamic properties, and structural characteristics of 5-cyano[n](2,4)pyridinophane-6-ones (n= 9-6) and their chemical transformations.

A novel synthesis of 5-cyano[n](2,4)pyridinophane-6-ones 12a-d (n= 9, 8, 7, and 6) consists of allowing cyanoacetatoamide to react with cycloalk-2-enones. Their static and dynamic properties as well as structural characteristics are studied on the basis of their spectroscopic properties, cyclic voltammetry, and theoretical calculations. The (1)H and (13)C NMR spectra at various temperatures have clarified the dynamic behavior of the methylene chains for [7](2,4)- and [6](2,4)pyridinophane-6-one derivatives 12c and 12d. The energy barrier (Delta G(++)) of the bridge flipping of 12c is estimated to be 12.0 kcal mol(-1)(T(c)= 0 degree C). On the other hand, compound 12d undergoes pseudorotation (conformational change of the methylene chain) at room temperature, and does not undergo bridge flipping even at 150 degree C in DMSO-d(6). The energy barrier (Delta G(++)) of the pseudorotation of the methylene chain 12d of is found to be 10.5 kcal mol(-1)(T(c)=-25 degree C), and thus, two stable conformers of the hexamethylene bridge of 12d are determined as predicted by theoretical calculations. Deformation of the pyridone ring of 12d is also determined by X-ray crystallographic analysis. Furthermore, chemical transformations of 12a-c leading to 5-carbamoyl[n](2,4)pyridinophanes 15a-c are also accomplished successfully in moderate to good yields.

Preparation of epoxy-based hybrid films from an aqueous TiO2 dispersion via solvent exchange and surface modification with n-octylphosphonic acid

Transparent TiO2/epoxy hybrid films with high refractive indices have been prepared from a 9-mass% aqueous TiO2 (rutile form) dispersion by a combination of dispersion medium exchange and surface modification with n-octylphosphonic acid (OPA). The dispersion medium was exchanged from H2O to N-methylformamide (NMF) by distilling off H2O after the addition of NMF. The TiO2 surface was then modified with OPA by heating at 80u2009°C for 24u2009h. IR and NMR spectra of the OPA-modified TiO2 nanoparticles (NPs) revealed that the OPA moiety was grafted onto the surface of the TiO2 NPs through Ti–O–P bonds. The resulting OPA-modified TiO2 NPs were employed to prepare epoxy-based hybrid films possessing excellent transparency. The transmittance in the entire visible range (400–800u2009nm) of the hybrid film containing 66.3u2009mass% TiO2 was above 94%. This hybrid film also exhibited the highest refractive index (nu2009=u20091.74), which represented a remarkable increase from that of the pure epoxy resin film (nu2009=u20091.51).

Synthesis, structure, and reactivity of (tropon-2-ylimino)arsorane and in situ generation of its stiborane and -bismuthorane analogues: reactions with heterocumulenes and an activated acetylene giving heteroazulenes

(Tropon-2-ylimino)pnictoranes of the general structure RNMPh3 (Rxa0=xa0tropon-2-yl; Mxa0=xa0As, Sb, and Bi) 4–6 have been prepared for the first time by the reaction of 2-aminotropone with Ph3MX2 (Mxa0=xa0As, Sb, and Bi) in the presence of a base. The arsorane derivative (Mxa0=xa0As) 4 is isolated as a stable crystalline compound, while the stiborane (Mxa0=xa0Sb) and the bismuthorane (Mxa0=xa0Bi) derivatives 5 and 6 are not isolated and are prepared in situ due to their moisture sensitivity. The X-ray crystal analysis revealed that compound 4 exhibits two different conformations in the solid state, and nthat the As–O bond distances (2.33 A) lie below the sum of the van der Waals radii (3.37 A), and thus, there is appreciable bonding interaction between the arsine and the oxygen atoms. With a view to constructing a series of cyclohepta-annulated heterocycles and in order to gain a better understanding of a series of iminopnictoranes, compounds 4–6 were allowed to react with heterocumulenes such as carbon disulfide, phenyl isothiocyanate, phenyl isocyanate, and diphenylcarbodiimide, in an aza-Wittig/electrocyclization or a formal [8xa0+xa02] type cycloaddition eliminating triphenylpnictorane oxide to give 2H-cycloheptaoxazol-2-one, its thione, and imine derivatives. On the other hand, the reaction of compounds 4 and 5 with dimethyl acetylenedicarboxylate (DMAD) gives postulated dimethyl cyclohepta[b]pyrrole-2,3-dicarboxylate, nwhich subsequently reacts with DMAD to result in the formation of tetramethyl 2H-cyclohepta[gh]pyrrolizine-1,2,4,5-tetracarboxylate, while the reaction of 6 gives only intractable tarry materials. The reactivity of the compounds 4–6, which contain a formal NM (Mxa0=xa0As, Sb, and Bi) double bond, has been clarified to be in the order of 6 (Mxa0=xa0Bi)xa0>xa05 (Mxa0=xa0Sb)xa0>xa04 (Mxa0=xa0As)xa0>xa0[the corresponding iminophosphorane derivative 3 (Mxa0=xa0P)].

Synthesis and Structure of 2-(Triphenylphosphoranylideneamino)tropone and its Utility in the Preparation of New Cyclohepta-annulated Heterocycles

2-(Triphenylphosphoranylideneamino)tropone is synthesized for the first time and treated with heterocumulenes to give novel cyclohepta-annulated heterocycles in good yields.