In Situ Processing of Nano Crystalline Oxide Particles/Polymer Hybrid

Nano sized crystalline particles/polymer hybrids were synthesized form designed metal-organic precursors. The newly developed method is composed of the synthesis of organic matrix by polymerization and the in situ nucleation and growth of crystalline oxide particles in the organic matrix below 100°C. The design of metal-organic precursor modified with polymerizable ligand and the selection of reaction conditions does influence the size and crystallinity of ceramic particles in organic matrix. The nano-sized magnetic particle/polymer hybrid exhibits the interesting feature of superparamagnetism and quantum size effect. The crystalline particles of BaTiO₃/, PbTiO₃/, and KNbO₃/polymer hybrids behave to be dielectric and show the typical electro-rheological behavior.     

Stereoselective syntheses of 4-hydroxy 4-substituted glutamic acids

The 4-hydroxy 4-substituted glutamic acid moiety is a common substructure of biologically important natural products such as monatin [(2S,4S)-2], lycoperdic acid (3), and dysiherbaine (4). To develop methodology for syntheses of these natural products, cycloadditions of nitrone 5 with 2-substituted 2-propen-1-ols 6 and 2-substituted acrylates 8 were investigated. Reactions of nitrone 5 with alcohols 6 in the presence of MgBr2OEt2 gave cycloadducts 7 in a highly stereoselective manner, whereas noncatalyzed reactions of 5 with acrylates 8 afforded adducts 9. Using the former reaction, syntheses of monatin [(2S,4S)-2], monatin derivative 18, and lycoperdic acid (3) were accomplished. The C4-epimer of monatin [(2S,4R)-2)] was also synthesized by employing the latter cycloaddition.     

Synthesis and two-electron redox behavior of diazuleno[2,1-a:1,2-c]naphthalenes

The Diels-Alder reaction of di-2-azulenylacetylene with tetraphenylcyclopentadienone afforded 7,8,9,10-tetraphenyldiazuleno[2,1-a:1,2-c]naphthalene in one pot via autoxidation of the presumed 1,2-di-2-azulenylbenzene derivative. In contrast, a similar reaction of bis(1-methoxycarbonyl-2-azulenyl)acetylene with tetraphenylcyclopentadienone gave the 1,2-di-2-azulenylbenzene derivative. The following cyclodehydrogenation reaction of the benzene derivative with iron(III) chloride afforded diazuleno[2,1-a:1,2-c]naphthalene 6,11-bismethoxycarbonyl derivative. The redox behavior of these novel diazuleno[2,1-a:1,2-c]naphthalenes was examined by cyclic voltammetry (CV). These compounds exhibited two-step oxidation waves at +0.22 to +0.71 V upon CV, which revealed the formation of a radical cation and dication stabilized by the fused two azulene rings under the electrochemical oxidation conditions. Since the 1,2-di-2-azulenylbenzene derivative was oxidized at higher oxidation potentials (+0.83 and +1.86 V), the fusion of the two azulene rings to naphthalene increased electron-donating properties because of the formation of a closed-shell dicationic structure. Formation of the radical cation was characterized by UV-vis spectroscopy under the electrochemical oxidation conditions, although no evidence was obtained for the presumed dication under the conditions of the UV-vis spectroscopy measurement.     

Furan ring oxidation strategy for the synthesis of macrosphelides A and B

By using the convenient protocol for conversion of 2-substituted furans into 4-oxo-2-alkenoic acids ((i) NBS, (ii) NaClO(2)), macrosphelide B (2) was synthesized from furyl alcohol 5 (>98% ee) and acid 6 (99% ee). The protocol was first applied to the PMB ether of 5 to afford acid 13b. On the other hand, DCC condensation of acid 6 with 5 gave 16 after deprotection of the TBS group. Condensation was again carried out between 13b and 16 to furnish the key ketone 17, which upon reduction with Zn(BH(4))(2) afforded anti alcohol 18 stereoselectively (15:1). After protection/deprotection steps, the furan 18 was converted to seco acid 3 by using the furan oxidation protocol mentioned above, and lactonization of 3 with Cl(3)C(6)H(2)COCl, Et(3)N, and DMAP afforded 22 (MOM ether of 2), which upon deprotection with TFA produced 2. Transformation of 22 to macrosphelide A (1) was then investigated. Although the chelation-controlled reduction of 22 should afford the desired anti alcohol 24, Zn(BH(4))(2) at <-90 degrees C gave a 2 approximately 1:1 mixture of anti/syn alcohols. On the contrary, reduction with NaBH(4) in MeOH at -15 degrees C produced the syn isomer 23 with >10:1 diastereoselectivity. Mitsunobu inversion of the resulting C(14)-hydroxyl group and deprotection of the MOM group with TFA afforded 1. Similarly, reduction of 2 with NaBH(4) afforded the C(14)-epimer of 1 stereoselectively. The observed stereoselectivity in the reductions of 22 and 2 could be explained on the basis of computer-assisted calculation, which showed presence of the low-energy conformers responsible for the stereoselective reduction. In addition, conversion of 2 to 1 was established, for the first time.     

Syntheses and electrical conductivity of polyamides containing tetrathiafulvalene moieties in the main chain

Novel polyamides that contain tetrathiafulvalene (TTF) moieties were synthesized by direct polycondensation of Δ^2,2′ -bi-1,3-dithiole-4,4′(5′)-dicarboxylic acid with aromatic diamines in the presence of triphenylphosphine, hexachloroethane, and pyridine. Complexes of these polyamides with bromine were TTF cation radical () salts which resulted from the charge transfer of TTF moieties to bromine. The electrical conductivity of undoped polyamides increased with a decrease in diamine length. By doping the bromine the conductivity of the polyamides was enhanced by 3–5 orders of magnitude and reached 10^?5–;10^?9S cm^?1. Maximum conductivity was observed at the doping ratio of [Br]/[repeat unit] < 1. The electrical conduction in the bromine complexes may be attributed to the hopping of odd electrons of between TTF moieties.     

alpha-Aminoallylation of aldehydes with ammonia: stereoselective synthesis of homoallylic primary amines

Three-component reactions of aldehydes, ammonia, and allylboronates were found to provide homoallylic primary amines in high yields with high chemo- and stereoselectivities. A two-step, one-pot, stereoselective synthesis of an uncommon alpha-amino acid, alloisoleucine, was achieved utilizing this reaction.     

Electronic structures of I2− and I4− ions in γ-irradiated rigid solutions

Radical-anions of iodine, bromine, and monoiodochloride are produced in γ-irradiated amorphous solids at 77 K, and their electronic and ESR spectra measured. On limited warming of the irradiated solution dimerization by the reaction I₂^? + I₂ → I₄^? occurs to produce the same species as reported by Fornier de Violet et al. The electronic structure of the dimeric anion is discussed in comparison with the monomeric anion.     

Thermal and palladium-catalyzed [3 + 2] synthesis of cyclopentadienone acetals from cyclopropenone acetals and acetylenes

[reaction: see text] Substituted cyclopentadienone acetals (CPDAs) were synthesized by a thermal or palladium-catalyzed [3 + 2] cycloaddition reaction of a substituted cyclopropenone acetal to an electron-deficient acetylene. The synthesis afforded di-, tri-, and tetra-substituted CPDAs of considerable structural varieties that undergo Diels-Alder reaction to produce bicyclo[2.2.1]heptenes.     

Dehydration reactions in water. Brønsted Acid-surfactant-combined catalyst for ester,ether, thioether,and dithioacetal formation in water

Dehydration reactions in water have been realized by a surfactant-type catalyst, dodecylbenzenesulfonic acid (DBSA). These reactions include dehydrative esterification, etherification, thioetherification, and dithioacetalization. In these reactions, DBSA and substrates form emulsion droplets whose interior is hydrophobic enough to exclude water molecules generated during the reactions. Detailed studies on the esterification revealed that the yields of esters were affected by temperature, amounts of DBSA used, and the substrates. Esters were obtained in high yields for highly hydrophobic substrates. On the basis of the difference in hydrophobicity of the substrates, unique selective esterification and etherification in water were attained. Furthermore, chemospecific, three-component reactions under DBSA-catalyzed conditions were also found to proceed smoothly. This work not only may lead to environmentally benign systems but also will provide a new aspect of organic chemistry in water.