Cationic copolymerization of indene with styrene derivatives: Synthesis of random copolymers of indene with high molecular weight

Random copolymers with high molecular weights of indene and p‐methylstyrene (pMeSt) were synthesized by cationic polymerization with trichloroacetic acid/tin tetrachloride in CH₂Cl₂ at low temperatures. When indene and pMeSt (1:1 v/v), for example, were polymerized at ?40 °C, both monomers were consumed at very similar rates to give a copolymer with high molecular weight [number‐average molecular weight (M_n): 8–9 × 10⁴]. This is indeed quite unexpected behavior for the combination of these two monomers because pMeSt polymerized over 1000 times faster than indene in the homopolymerization under the reaction conditions previously described. The product copolymer of indene and pMeSt had a random monomer sequence in it that was confirmed by NMR analyses and thermal‐property measurements. In sharp contrast with pMeSt, styrene and p‐chlorostyrene, which have no electron‐donating groups on the phenyl ring, led to low molecular weight polymers (M_n < 10,000) in the copolymerization with indene (1:1 v/v). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2449–2457, 2002     

Enantioselective carbanion cyclization of 5-alkenyl carbamates induced by asymmetric lithiation with s-butyllithium/(−)-sparteine system

Treatment of (E)-6-phenyl-5-hexenyl carbamates with s-BuLi/(−)-sparteine is shown to afford the trans-1,2-disubstituted cyclopentane derivatives in high % ee, along with the bicyclo[3.1.0]hexanes (bicyclization products).     

Synthesis and pharmacological evaluation of pyrroloazepine derivatives as potent antihypertensive agents with antiplatelet aggregation activity

A series of 1-aminoalkyl-pyrrolo[2,3-c]azepin-8-one derivatives was synthesized and evaluated as alpha 1 adrenergic and serotonin 2 (5-HT2) receptor antagonists, with the aim of finding a novel antihypertensive agent potently exhibiting both activities. Some compounds with a 4-[4-(4-fluorobenzoyl)piperidino]butyl group at the 1-position exhibited both activities, and varied significantly in terms of the substituents at the 4-position of the pyrroloazepine ring. Among the compounds obtained in this study, (E)-1-[4-[4-(4-fluorobenzoyl)piperidino]-butyl]-4-hydroxyimino-7- methyl-1,4,5,6,7,8-hexahydropyrrolo[2,3-c]azepin-8-one (15a, SUN9221) displayed potent alpha 1-adrenergic antagonistic activity (pA2 = 8.89 +/- 0.21) and 5-HT2 antagonistic activity (pA2 = 8.74 +/- 0.22) in isolated guinea pig arteries. This compound exhibited antihypertensive activity and a duration of action equivalent to orally administered prazosin or doxazosin, 3 mg/kg, in conscious spontaneously hypertensive rats, as well as potent antiplatelet aggregation activity.     

Time-dependent density functional theory calculations of the photoabsorption of fluorinated alkanes

Time-dependent density functional theory (TD-DFT) calculations of the transition energies and oscillator strengths of fluorinated alkanes have been performed. The TD-DFT method with the non-local B3LYP potential yields transition energies for the methanes, which are smaller by about 10% as compared to the experimental values. An empirical linear correlation was found between the calculated and experimental transition energies both at the B3LYP/DZ+Ryd(C, F) and B3LYP/cc-pVTZ+Ryd(C, F, H) levels for a total of 19 transitions of the fluorinated methanes with linear correlation coefficients of 0.987 for the former and 0.988 for the latter. This empirical correlation for fluorinated methane molecules is found to agree well with the previously obtained empirical correlations between calculated and experimental values for non-fluorinated molecules. The results show that a single empirical-correlation relationship can be used for both non-fluorinated and fluorinated molecules to predict transition energies. This linear relationship is then used to predict the photoabsorption spectra of ethane, propane, butane, and partially and fully fluorinated derivatives. A key result of these calculations is the dominance of Rydberg transitions in the spectral region of interest.     

Unambiguous Determination of the Absolute Configurations of Acetylene Alcohols by Combination of the Sonogashira Reaction and the CD Exciton Chirality Method – Exciton Coupling between Phenylacetylene and Benzoate Chromophores

The CD exciton chirality method was applied to various phenylacetylene alcohols to determine their absolute configurations; the long axis polarized –^* transition (_max=252nm) of the 4-methoxyphenylacetylene chromophore couples with the transition (_max=257nm) of the 4-methoxybenzoate group to generate intense exciton split CD Cotton effects, from the signs of which the absolute configurations of phenylacetylene alcohols were unambiguously determined. As an extension of the results, a new methodology for determining the absolute configurations of acetylene alcohols having the HCCCH(OH)-moiety by combination of the Sonogashira reaction and the CD exciton chirality method has been developed and applied. Since the –^* transition of acetylene triple bond is located below 180nm, it is difficult to observe ideal bisignate CD Cotton effects due to the exciton coupling between acetylene and benzoate chromophores. To observe the ideal exciton split Cotton effects necessary for the unambiguous determination of absolute configuration, the terminal acetylene group was converted, by the Sonogashira reaction, to the 4-methoxyphenylacetylene moiety, which exhibits an intense –^* absorption band polarized along the long axis of the chromophore at 252nm. As a partner of exciton coupling, 4-methoxybenzoate showing a –^* band at 257nm was introduced into the alcohol moiety, and the benzoates formed showed intense bisignate CD Cotton effects, from the signs of which the absolute configurations of original acetylene alcohols could be determined in an unambiguous manner.     

Comparative characterization study of microporous carbons by HRTEM image analysis and gas adsorption

The present work presents a useful comparison of micropore size distributions (MPSDs) obtained from gas adsorption and image analysis of high-resolution transmission electron micrographs. It is shown that the MPSD obtained for a chemical activated carbon is concordant with that obtained from CO2 adsorption. In addition, this technique has allowed us to obtain the MPSD of a carbon molecular sieve (CMS) prepared in our laboratory by a copyrolysis process, which could only be characterized by CO2 adsorption at 273 K (not by N2 adsorption at 77 K due to diffusional problems). The MPSD obtained by high-resolution transmission electron microscopy (HRTEM) for the CMS is wider than that obtained by CO2 adsorption, suggesting that HRTEM is detecting the closed porosity existing in this sample, which is not accessible to gas adsorption. The existence of closed porosity in the CMS is explained considering the preparation method used. Thus, HRTEM combined with image analysis seems to be useful for structural analysis of narrow micropores including closed porosity.     

Synthesis of Indolones via Radical Cyclization of N‐(2‐Halogenoalkanoyl)‐Substituted Anilines

The radical reactions of N‐(2‐halogenoalkanoyl)‐substituted anilines (anilides) of type 1 have been investigated under various conditions. Treatment of compounds 1a – 1o with Bu₃SnH in the presence of (2,2′‐azobis(isobutyronitrile) (AIBN) afforded a mixture of the indolones (oxindoles) 2a – 2o and the reduction products 5a – 5o (Table 1). In contrast, the N‐unsubstituted anilides 1p – 1s, 1u , and 1v gave the corresponding reduction products exclusively (Table 1). Similar results were obtained by treatment of 1 with Ni powder (Table 2) or wth Et₃B (Table 3). Anilides with longer N‐(phenylalkyl) chains such as 6 and 7 were inert towards radical cyclization, with the exception of N‐benzyl‐2‐bromo‐N,2‐dimethylpropanamide ( 6b ), which, upon treatment with Ni powder in i‐PrOH, afforded the cyclized product 9b in low yield (Table 4). Upon irradiation, the extended anilides 6, 7, 10 , and 11 yielded the corresponding dehydrobromination products exclusively (Table 5).     

Synthesis and structural,electrochemical, and optical properties of Ru(II) complexes with azobis(2,2'-bipyridine)s

Two new ditopic ligands, 5,5"-azobis(2,2'-bipyridine) (5,5"-azo) and 5,5"-azoxybis(2,2'-bipyridine) (5,5"-azoxy), were prepared by the reduction of nitro precursors. Mononuclear and dinuclear Ru(II) complexes having one of these bridging ligands and 2,2'-bipyridine terminal ligands were also prepared, and their properties were compared with previously reported Ru(II) complexes having 4,4"-azobis(2,2'-bipyridine) (4,4"-azo). The X-ray crystal structure showed that 5,5"-azo adopts the trans conformation and a planar rodlike shape. The X-ray crystal structure of [(bpy)(2)Ru(5,5"-azo)Ru(bpy)(2)](PF(6))(4) (Ru(5,5"-azo)Ru) showed that the bridging ligand is in the trans conformation and nearly planar also in the complex and the metal-to-metal distance is 10.0 A. The azo or azoxy ligand in these complexes exhibits reduction processes at less negative potentials than the terminal bpy's due to the low-lying pi level. The electronic absorption spectra for the complexes having 5,5"-azo or 5,5"-azoxy exhibit an extended low-energy metal-to-ligand charge-transfer absorption. The ligands, 5,5"-azo and 5,5"-azoxy, and the mononuclear complex, [(bpy)(2)Ru(5,5"-azo)](2+), isomerize reversibly upon light irradiation. The low-energy MLCT state sensitizes the isomerization of the azo moiety in this complex. While [(bpy)(2)Ru(4,4"-azo)Ru(bpy)(2)](PF(6))(4) exhibits light switch properties, namely, significant electrochromism and a large luminescence enhancement, upon reduction, Ru(5,5"-azo)Ru does not show these properties. The radical anion formation upon reduction of these complexes has been confirmed by ESR spectroscopy.     

Decarboxylation of α-keto carboxylic acids by persulfoxide

Photosensitized oxygenation of diethyl sulfide in the presence of α-keto carboxylic acids caused oxidative decarboxylation of the acids by persulfoxide and gave carboxylic acids, carbon dioxide, diethyl sulfoxide and diethyl sulfone.     

Rapid and simultaneous analysis of dichlorvos, malathion, carbaryl, and 2,4-dichlorophenoxy acetic acid in citrus fruit by flow-injection ion spray ionization tandem mass spectrometry

A simple method for the rapid and simultaneous analysis of dichlorvos (DDVP), malathion, carbaryl, and 2,4-dichlorophenoxy acetic acid (2,4-D) in citrus fruit, which uses flow-injection ion spray ionization tandem mass spectrometry, has been developed for the first time. The method involves the combined use of stable isotopically labeled internal standards (DDVP-d₆, malathion-d₁₀, carbaryl-d₇, and 2,4-D-d₅) and a multiple reaction monitoring technique. The average recoveries for the pesticides at the same concentrations as their tolerance levels (DDVP: 0.1-0.2 μg g⁻¹; malathion: 0.5-4.0 μg g⁻¹; carbaryl: 1.0 μg g⁻¹; 2,4-D: 1.0-2.0 μg g⁻¹) ranged from 90 to 119% with the relative standard deviation (R.S.D.) ranging from 1.0 to 13.1% (n = 5). Analysis time, including sample preparation and determination, was only 15 min. The present method is effective for screening DDVP, malathion, carbaryl, and 2,4-D in citrus fruit.