横山 明弘

Chain-growth condensation polymerization of 2-bromo-5-chloromagnesio-3-[2-(2-methoxyethoxy)ethoxylmethylthiophene (2) with Ni catalysts was studied, and the block copolymer of poly2 and poly(3-hexylthiophene) was synthesized by this polymerization method. The polymerization of 2 depended on the ligands of the Ni catalyst, and poly2 with the lowest polydispersity was obtained when 1,2-bis(diphenylphosphino)ethane (dppe) was used as the ligand. The linear relationships between the conversion of 2 and M-n of the polymer and between the feed ratio of 2 to the Ni catalyst and Mn of the polymer indicate that this polymerization proceeds in a chain-growth polymerization manner via a catalyst-transfer condensation polymerization mechanism. The block copolymerization of 2 and 2-bromo5-chloromagnesio-3-hexylthiophene (1) was then carried out in four ways by changing the order of polymerization of the two monomers and the catalysts. It turned out that the block copolymer was obtained without the formation of the homopolymers by the polymerization of 1 with Ni(dppe)Cl2 or Ni(dppP)Cl2 (dppp = 1,2-bis(diphenylphosphino)propane), followed by the postpolymerization of 2. Of the two catalysts, Ni(dppe)Cl-2 resulted in narrower polydispersity of the block copolymer.

Well-defined diblock copolymers of polystyrene and aromatic polyether were synthesized by the combination of atom transfer radical polymerization (ATRP) and chain-growth condensation polymerization (CGCP) from an orthogonal initiator. A polystyrene macroinitiator was first synthesized by the ATRP of styrene in the presence of 4-fluorobenzenesulfonyl chloride (FBS-Cl) as an orthogonal initiator, then the terminal chlorine of the polystyrene was dehalogenated with Et3SiH/Pd(OAc)(2). The CGCP of potassium 5-cyano-4-fluoro-2-propylphenolate (1) was then carried out with the polystyrene macroinitiator in sulfolane at 150 degrees C. However, not only polystyrene-b-aromatic polyether but also macrocycles of 1 were obtained, due to transetherification of the p-sulfonylphenyl ether linkage of the macroinitiator with 1. In contrast, the CGCP of 1 from another polystyrene macroinitiator bearing a keto group, which was prepared similarly by the ATRP of styrene with 4-(1-bromoethyl)-4'-fluorobenzophenone (FBP-Br) as an orthogonal initiator, followed by reduction of the terminal C-Br bond with Bu3SnH, afforded only well-defined polystyrene-b-aromatic polyether. This diblock copolymer self-assembled in THF to form spherical aggregates.

Palladium-catalyzed polycondensation of 2-(7-bromo-9,9-dioctyl-9H-fluoren-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (1a) with (Bu3PPd)-Bu-t(Ph)Br (2) via Suzuki-Miyaura coupling reaction was investigated. The polymerization in a mixture of THF and 2 mol/L aqueous solution of Na2CO3 proceeded smoothly at room temperature and afforded well-defined polyfluorenes with narrow molecular weight distributions. MALDI-TOF mass spectroscopy showed that the obtained polymers have a phenyl group at one end. The relationships of conversion to number-average molecular weight (M-n) and feed ratio to M-n were linear. These results demonstrate that this organometallic polycondensation proceeds through a chain-growth polymerization mechanism from an initiator unit derived from the catalyst.

Chain-growth polycondensation of 3-(alkylamino)benzoic acid alkyl esters 1 was investigated for obtaining poly(m-benzamide)s with defined molecular weights and low polydispersities. Polymerization conditions were first studied to find that ethyl 3-(octylamino)benzoate (1b) polymerized in a chain polymerization manner in the presence of lithium 1,1,1,3,3,3-hexamethyldisilazide (LiHMDS) as a base and phenyl 4-methylbenzoate (2b) as an initiator in THF at 0 °C. The molecular weight of the polymer was controlled by the feed ratio of monomer to initiator. The polymerization of 1c-i with a variety of N-alkyl groups was then carried out under the established conditions to yield well-defined poly(m-benzamide)s, which showed higher solubility than those of the corresponding poly(p-benzamide)s. Furthermore, the 4-octyl-oxybenzyl group on the amide nitrogen in polyli was removed by treatment with trifluoroacetic acid (TFA) to give N-unsubstituted poly(m-benzamide) (poly1j) with a low polydispersity, which is soluble in DMAc and DMSO, contrary to the para-substituted counterpart. © 2006 Wiley Periodicals, Inc.

Chain-growth polycondensations of 3-aminobenzoic acid methyl esters 1a and 1b, bearing a' tri- or tetra(ethylene glycol) methyl ether unit on the amino group, respectively, were carried out with lithium hexamethyldisilazide (LiHMDS) as a base and phenyl 4-methylbenzoate (2) as an initiator in THF at 0° C. The poly(m-benzamide)s obtained in the presence of N,N,N′N′- tetramethylethylenediamine (TMEDA) possessed narrow molecular weight distributions (M̄ w/M u < 1.2) with molecular weights that were determined by the feed ratios of [1] 0/[2] 0. Poly1a and poly1b were each soluble in water and exhibited a lower critical solution temperature (LCST) in water. Furthermore, the phase separation in water depended on the length of the oligo(ethylene glycol) side chain and on the molecular weight and molecular weight distribution of poly1. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA.

Acetalization of aromatic aldehydes 1 with bis(trimethylsilyl ether)s 2 or 4 in the presence of a Lewis-acid catalyst was investigated. Under the optimized conditions, this reaction initially gave a mixture of oligomers, which converged to a [2 + 2] macrocycle in high yield via reversible transacetalation.

We studied the mechanism of the chain-growth polymerization of 2-bromo-5-chloromagnesio3-hexylthiophene (1) with Ni(dppp)Cl-2 [dppp = 1,3-bis(diphenylphosphino)propane], in which head-to-tail poly(3-hexylthiophene) (HT-P3HT) with a low polydispersity is obtained and the M-n is controlled by the feed ratio of the monomer to the Ni catalyst. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectra showed that the HT-P3HT uniformly had a hydrogen atom at one end of each molecule and a bromine atom at the other. The reaction of the polymer with aryl Grignard reagent gave HT-P3HT with aryl groups at both ends, which indicates that the H-end was derived from the propagating Ni complex. The degree of polymerization and the absolute molecular weight of the polymer could be evaluated from the H-1 NMR spectra of the Ar/Ar-ended HT-P3HT, and it was found that one Ni catalyst molecule forms one polymer chain. Furthermore, by reaction of 1 with 50 mol % Ni(dppp)Cl-2, the chain initiator was found to be a bithiophene-Ni complex, formed by a coupling reaction of 1 followed by insertion of the Ni(0) catalyst into the C-Br bond of the dimer. On the basis of these results, we propose that this chain-growth polymerization involves the coupling reaction of 1 with the polymer via the Ni catalyst, which is transferred intramolecularly to the terminal C-Br bond of the elongated molecule. We call this mechanism "catalyst-transfer polycondensation".

For the synthesis of aromatic polyesters with defined molecular weights and narrow molecular weight distributions (MWDs), we investigated the chain-growth polycondensation of active amide derivatives of 4-hydroxybenzoic acid, la and 1b, having an octyl or 4,7-dioxaoctyl side chain, respectively. To suppress the transesterification of the polymer backbone with the monomer, the polymerization of I was carried out in tetrahydrofuran (THF) at -30 degrees C in the presence of initiator 2 and Et3SiH/CsF/18-crown-6, which generated a hydride ion as a base in situ. The number-average molecular weight (Mu) of poly1a was controlled, and narrow MWDs were maintained, until the [1a](0)/[2](0) feed ratio was 14.3 (M-n <= 3500), whereas that of poly1b was controlled until the feed ratio was 30 (M-n <= 7250). The difference stemmed from the higher solubility of poly1b in THF. This chain-growth polycondensation was applied to the synthesis of a diblock copolyester of la and 1b of a defined architecture. (c) 2005 Wiley Periodicals, Inc.

Treatment of 4-(alkylamino)benzoic acid dimer phenyl esters with a base, under conditions where monomeric 4-(alkylamino)benzoic acid phenyl esters polymerize to give well-defined aromatic polyamides, affords not polymers, but cyclic trimers in good yield.

Poly(p-benzamide)s 1 bearing a chiral side chain on the nitrogen atom were synthesized by chain-growth polycondensation methodology. The polyamides exhibited well-defined molecular weights with narrow polydispersities. Solutions of the polyamides in several organic solvents (CH3CN, CHCl 3, and CH3OH) showed dispersion type CD signals characteristic of coupled-oscillator and much larger as compared with the corresponding monomer. The CD signals were dependent on the temperature and molecular weight of the polyamides but independent of the solvent, as far as examined. An exciton model analysis of the absorption and CD spectra provided a clear-cut picture for the secondary structure of these polyamides in solution that the N-alkylated poly(p-benzamide)s possess a right-handed helical conformation ((P)-helix). In the solid states, the results of X-ray crystallographic analysis of 4-(methylamino)benzoic acid oligomers substantiated that they have a helical conformation with three monomer units per turn. © 2005 American Chemical Society.

For the convenient synthesis of well-defined poly(N-octyl-p-benzamide)s with low polydispersities, the polycondensation of methyl 4-octylaminobenzoate (1) was investigated. Methyl ester monomer 1 polymerized with lithium 1,1,1,3,3,3-hexamethyldisilazide (LHMDS) in the presence of an initiator in tetrahydrofuran at -10 degrees C. The highly pure polyamide with a defined molecular weight and a low polydispersity is obtained after simple treatment of the reaction mixture with aqueous NaOH solution, followed by evaporation.

For the synthesis of well-defined star-shaped aromatic polyamides, triphenyl benzene-1,3,5-tricarboxylate (2a), tetraphenyl benzene-1,2,4,5-tetracarboxylate (2b), and 1,3,5-tris(4-phenyloxycarbonylbenzyloxy)benzene (3) were synthesized and then employed as multifunctional initiators for the chain-growth polymerization of phenyl 4-(octylamino)benzoate (1). The polymerization with 2a or 2b did not proceed smoothly from all of the phenyl ester moieties in the initiators and afforded polymers with high polydispersities. In contrast, initiator 3 having the benzyloxy spacers resulted in three-armed aromatic polyamide (1) with low polydispersity. Furthermore, the benzyloxy linkages of the core of I were cleaved by hydrogenolysis to yield a polymer with low polydispersity, the M-n of which was one-third that of 1, indicating that I exactly possesses three arm chains of a uniform and controlled length. However, the polymerization at higher feed ratios of [1](0)/[3](0) afforded not only the three-armed polymer but also a linear polymer formed by self-polymerization of 1.

The helical structure of poly(p-benzamide)s (1) bearing a chiral side chain on the nitrogen atom was investigated by UV and CD spectroscopy. The polymers exhibited bisignate CD and much larger compared with the corresponding monomer (2). By applying the coupled oscillator analysis in conjunction with TDDFT calculations, the positive and negative CD signals observed at 300 and 260 nm, respectively, could be assigned to the exciton band arising from the couplings of the long-axis polarized transition of each 4-(alkylamino)benzoyl chromophore. Taking into account the Rosenfeld equation, we assigned the helical sense of the polymers to be right-handed ((P)-helix).

The historical development of our research on polycondensation that proceeds in a chain-growth polymerization manner ("chain-growth polycondensation") for well-defined condensation polymers is described. We first studied polycondensation in which change of the substituent effect induced by bond formation drove the reactivity of the polymer end group higher than that of the monomer. In this approach, well-defined aromatic polyamides, polyesters, polyethers, and poly(ether sulfone)s were obtained. The second approach was the study of the phase-transfer polymerization of a solid monomer dispersed in an organic solvent. In this type of polymerization, the solid monomer was physically unable to react with another monomer and was carried with the phase transfer catalyst into the solution phase where it reacted with an initiator and the polymer end group in the solvent in a chain polymerization manner. We also found catalyst-transfer polycondensation as a third approach to chain-growth polycondensation. In the Ni-catalyzed polycondensation of 2-bromo-5-chloromagnesiothiophenes, the Ni catalyst transferred to the polymer end group, and a coupling reaction occurred there to yield a well-defined polythiophene. This chain-growth polycondensation was applied to the synthesis of condensation polymer architectures such as block copolymers, star polymers, graft copolymers, and so on. © 2005 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.

The polymerization of 2-bromo-3-hexyl-5-iodothiophene (1) with isopropylmagnesium chloride and Ni(dppp)Cl-2 was quenched with 5 M hydrochloric acid instead of water to yield head-to-tail poly(3-hexylthiophene) (HT-P3HT) with a very low polydispersity. The (M) over bar (n) of the polymer was controlled by the feed ratio of 1 to Ni(dppp)Cl2. Quenching with 5 M hydrochloric acid seemed to promote protonolysis of HT-P3HT-Ni complexes before the coupling reaction between HT-P3HT.

A resolution revolution? Self-assembled chiral structures resulting from the formation of two different helical interactions are found in the crystal structures of the achiral compound 1. The interactions give rise to Ar-H⋯π and OH⋯O=C arrays. The chirality of the helices is spontaneously resolved within individual single crystals. Only one of the hydroxy groups contributes to the formation of a helical hydrogen-bonding array (shown in green).

The polycondensation of potassium 5-cyano-4-fluoro-2-octylphenolate (1b) was carried out in the presence of 4-fluoro-4'-trifluoromethylbenzophenone (2) as an initiator for chain-growth polycondensation in a variety of solvents, and the chain-growth nature of this polymerization was found to depend on the kind of solvent. In the polycondensation of 1b with 2 in sulfolane at 150 degreesC, the. MALDI-TOF mass spectra of poly1b showed only one series of peaks due to poly1b attached with the initiator 2 unit, and the F-19 NMR spectra indicated that the ratios of the initiator unit to the end group were 1.0. Therefore, chain-growth polycondensation occured in this condition. On the other hand, the polycondensation in THF, quinoline, DMI, tetraglyme at 150 degreesC gave poly1b with broad molecular weight distributions, and the MALDI-TOF mass spectra showed two series of peaks resulting from both chain-growth and step-growth polycondensations. (C) 2004 Wiley Periodicals, Inc.

The polycondensation of phenyl 4-(octylamino)benzoate (1) proceeded in a chain-polymerization manner to yield aromatic polyamides with low polydispersities (M-W/M-n less than or equal to 1.1) even under normal conditions for step-growth polycondensation, in which initiator was not added. On the basis of the results of the polycondesations of 1 with initiator models, this self-initiated chain-growth polycondensation involves the formation of the dimer of 1, which initiates the chain-growth polymerization faster than step-growth polymerization.

Well-defined telechelic-type aromatic polyamides having a secondary amino group and a phenyl ester moiety at each chain end were prepared by the chain-growth polycondensation of phenyl 4-(octylamino)benzoate (1) with initiator 2 (N-tert-butoxycarbonylated 1) followed by deprotection of the N-protecting group of the initiator unit. This polycondensation was applied to the synthesis of well-defined di- and triblock copolymers of aromatic polyamides and poly(tetrahydrofuran) (poly(THF)) by the reaction of the terminal secondary amino group of the polyamide with the living cationic propagating group of poly(THF).

Polycondensation normally proceeds in a step-growth reaction manner to give polymers with a wide range of molecular weights. However, the polycondensation of potassium 2-alkyl-5-cyano-4-fluorophenolate (1) proceeded at 150 degreesC in a chain polymerization manner from initiator, 4-fluoro-4'-trifluoromethyl benzophenone (2), to give aromatic polyethers having controlled molecular weights and low polydispersities (M-w/M-n less than or equal to 1.2). The resulting polycondensation of 1 had all of the characteristics of living polymerization and displayed a linear correlation between molecular weight and monomer conversion, maintaining low polydispersities. Sulfolane was a better solvent for chain-growth polycondensation of 1 than other aprotic solvents. The polyether from 1 with a low polydispersity showed higher crystallinity than that with a broad molecular weight distribution, obtained by the conventional polycondensation of 1 without 2.

Poly(p-benzamide) with a defined molecular weight and a low polydispersity and block copolymers containing this well-defined aramide was synthesized. Phenyl 4-(4-octyloxybenzylamino)benzoate (1b) polymerized at room temperature in the presence of base and phenyl 4-nitrobenzoate (2a) as an initiator in a chain-growth polycondensation manner to give well-defined aromatic polyamides having the 4-octyloxybenzyl groups as a protecting group on nitrogen in an amide. It was confirmed by a model reaction that deprotection of this protecting group proceeded completely with trifluoroacetic acid (TFA) without breaking the amide linkage, The utility of this approach to poly(P-benzamide) with a low polydispersity was demonstrated by the synthesis of block copolymers of poly(p-benzamide) and poly(N-octyl-p-benzamide) or poly(ethylene glycol). The SEM images of the supramolecular assemblies of the former block copolymer showed pm-sized bundles and aggregates of flake structures.

Polycondensation normally proceeds in a step-growth reaction manner to give polymers with a wide range of molecular weights. However, the polycondensation of potassium 5-cyano-4-fluoro-2-propylphenolate (1) proceeded at 150 degreesC in a chain polymerization manner from an initiator, 4-fluoro-4'-trifluoromethylbenzophenone (2a), to give aromatic polyethers having controlled molecular weights and low polydispersities (M-w/M-n less than or equal to 1.1). The resulting polycondensation of 1 had all of the characteristics of living polymerization and displayed a linear correlation between molecular weight and monomer conversion, maintaining low polydispersities. The MALDI-TOF mass spectrum of poly1 revealed that this polycondensation did not include conventional step-growth polycondensation which gave the polymer without initiation unit and macrocycles. The poly1 with low polydispersity showed higher crystallinity than that with broad molecular weight distribution, obtained by the conventional polycondensation of 1 without 2a.

Synthesis of aromatic polyesters by chain-growth polycondensation of activated 4-hydroxybenzoic acid derivatives (1) was investigated. Model reactions of ester formation between active compounds (6 and 7) and phenolic nucleophile (8) gave the best result when 3-arylcarbonyl-2-benzothiazolone derivatives were used with tertiary amines in CH2Cl2. Therefore, we designed and synthesized 3-(4-hydroxy-3-octylbenzoyl)-2-benzothiazolone (1h) as a monomer. The Mn- and M-W/M-n-conversion curves of the polymerization of 1h with initiator suggested that transesterification between polymer and monomer occurred in the late stage of polymerization. Investigation of the effects of bases and initiators revealed that the transesterification at the initiator end was minimized by using 3-(4-benzoyloxybenzoyl)-2benzothiazolone (7h) and diisopropylethylamine as an initiator and a base, respectively. When the ratio of initiator 7h to monomer 1h was 20 mol %, the polycondensation proceeded in a chain-growth manner to give aromatic polyester having a controlled molecular weight and a low polydispersity. However, the polymerization of 1h with 10 mol % or less of 7h could not be controlled and gave step-growth polymer as well as chain-growth polymer. The model reaction demonstrated that transesterification would occur at the polymer main chain even by use of weak tertiary amines as a base.

Polycondensation of phenyl 4-(octylamino)benzoate (1) in the presence of diphenyl terephthalate (2) as a difunctional initiator proceeded in a bidirectional propagation from 2. This polycondensation was applied to the synthesis of poly(ethylene glycol) (PEG)-aromatic polyamide-PEG triblock copolymer (4) as a new, well-defined coil-rod-coil triblock copolymer.

[GRAPHICS] Introduction of a hydrogen-bonding substituent to 1-cyanonaphthalene and alkene resulted in the selective formations of endo-photocycloadducs. Furthermore, the yield and selectivity were improved as the reaction temperature was lowered.

The size and position of a hydrophobic moiety on a benzolactam skeleton, which reproduces the active conformation and biological activity of teleocidins, play an important role in the appearance of the activity. Compounds with alkyl groups of various sizes and shapes at the 2-position of benzolactam were synthesized. Structure-activity results indicate that a hydrophobic substituent at the C-2 position plays a critical role in the appearance of biological activities, as in the case of substitution at C-9. (C) 1999 Elsevier Science Ltd. All rights reserved.

The Pictet-Spengler reaction, an acid-catalyzed intramolecular cyclization of intermediate imines of 2-arylethylamine to give 1,2,3,4-tetrahydroisoquinolines, has long been limited to active substrates which bear strongly electron-donating groups such as a methoxy or a hydroxy group on the cyclizing benzene ring. in this paper, we present superacid-catalyzed Pictet-Spengler reactions of imines of a-phenethylamine, including the prototype Pictet-Spengler reaction of N-methylene-2-phenethylamine, to give the parent and 1-substituted 1,2,3,4-tetrahydroisoquinolines in moderate to high yields. The yields are dependent on the acidity of the media. A linear relationship was found between the rate of the cyclization and the acidity of the reaction media in kinetic studies of N-methylene-2-phenethylamine and related imines, strongly supporting the intervention of an additional protonative activation of the N-protonated imines, that is, the involvement of dicationic superelectrophiles, N,N-diprotonated imines (ammonium-carbenium dications). We further found that the prototype cyclization of the parent N-methylene-2-phenethylamine is also catalyzed by TFA to give 1,2,3,4-tetrahydroisoquinoline in good yield, although the cyclization is significantly slower than that catalyzed by superacids. The prototype Pictet-Spengler cyclization of N-methylene-2-phenethylamine can thus take place both through the monocation (the N-monoprotonated imine) and the dication (the N,N-diprotonated imine), the latter reaction being predominant in superacids.

The acidity dependence of orientation in the nitration of quinoline 1-oxide was investigated by using the trifluoromethanesulfonic acid (TFSA)-trifluoroacetic acid (TFA) system and the antimony pentafluoride (SbF5)-TFSA system, These systems provide a wider range of acidity than that of aqueous sulfuric acid, Comparison of the behavior of quinoline 1-oxide and 1-methoxyquinolinium triflate in acidic and neutral media demonstrated that O-protonated quinoline 1-oxide is nitrated at the 5- and 8-positions, and the free (unprotonated) molecule is nitrated at the l-position. This result is consistent with theoretical expectation. It was also discovered that nitration at the 5-position increasingly predominates over that at the 8-position as the acidity is increased.