Effect of solvent in radical polymerization of butadiene 1-carboxylic acid

The radical polymerization and copolymerization of butadiene 1-carboxylic acid (Bu-1-Acid) were studied in a variety of the electron-donor solvents such as dimethylformamide (DMF), tetrahydrofuran (THF), methyl ethyl ketone (MEK), acetonitrile (ACN), and benzene (BZ) using AIBN as an initiator at 50°C. Under these conditions, the polymerization rate of Bu-1-Acid increased in the order, DMF < THF < MEK < ACN < BZ in the various solvents. In copolymerization with styrene [M₂] and acrylonitrile [M₂], the monomer reactivity ratio r₁ increased and r₂ decreased in the same order. Moreover, it was found that Alfrey-Price Q-e value of Bu-1-Acid increased depending on solvent in the order DMF < THF < MEK < ACN < BZ. These variations were correlated to the electron-donating power (Δvcm^?) of the solvents used and are discussed on the basis of the solvation of Bu-1-Acid into the solvent. Also, it was found that the microstructures of these polymers were always trans-1,4 and did not change with the solvent used.     

Effect of pH on radical polymerization of butadiene 1-carboxylic acid in aqueous solutions

Radical polymerization of butadiene 1-carboxylic acid (Bu-1-Acid) was carried out in aqueous solutions at 50°C with ammonium persulfate (APS) as an initiator. Kinetic studies led to the rate equation, R_p = k[APS]^1/2 [Bu-1-Acid]¹ at pH 6.8. The overall activation energy for the polymerization was 16.0 kcal/mole. The polymerization rate R_p of Bu-1-Acid decreased with an increase of pH in the range 2.4–6.8 and increased with an increase of pH in the range 6.8–8.4. Moreover, in the pH range 8.4–13, the rate of polymerization was not affected by the pH of the system. In copolymerization with acrylonitrile, the trends of changes in the monomer reactivity ratios r₁, r₂ and Q-e values caused by changes in pH were similar to trends found in homopolymerization described above. In addition, it was observed that the resultant polymer was extended in alkaline solution and contracted in acidic solution.     

Radical polymerization of butadiene-1-carboxylic acid

The homopolymerization and copolymerization of butadiene-1-carboxylic acid (Bu-1-Acid) (M₁) were studied in tetrahydrofuran at 50°C with azobisisobutyronitrile as an initiator. The initial rate of polymerization was proportional to [AIBN]^1/2 and [Bu-1-Acid]¹. The overall activation energy for the polymerization was 22.87 kcal/mole. For copolymerization with styrene (M₂) and acrylonitrile (M₂), the monomer reactivity ratios r₁, r₂ were determined by the Fineman-Ross method, as follows; r₁ = 5.55, r₂ = 0.08 (M₂ = styrene); r₁ = 11.0, r₂ = 0.03 (M₂ = acrylonitrile). Alfrey-Price Q-e values calculated from these values were 6.0 and +0.11, respectively. The Bu-1-Acid unit in the copolymer as well as the homopolymer was found from infrared and NMR spectral analyses to be composed of a trans-1,4 bond. The hydrogen-transfer polymerization of Bu-1-Acid leading to polyester was attempted with triphenylphosphine as initiator, but did not occur.     

Asymmetric radical copolymerization of S(−)-α-phenethylammonium butadiene 1-carboxylate with styrene

Radical copolymerization of S(?)-α-phenethylammonium butadiene 1-carboxylate (S-PBu) with styrene was performed in methanol, using azo-bis-isobutyronitrile as initiator. It was confirmed that the copolymers had trans 1,4 units of S-PBu; the copolymers after removal of chiral side chain were optically active. From CD spectra of the copolymers after removal of chiral amine from the side chain, it was found that the asymmetric induction occurred in the copolymer main chain. The copolymerization parameters of S-PBu were determined and are discussed.     

Controlled/living radical polymerization of isoprene and butadiene in emulsion

A process for RAFT-controlled radical polymerization in emulsion [36] has been applied to the polymerizations of isoprene and of butadiene in emulsion systems, with the goal of producing latex particles containing block copolymers of acrylic acid (stabilizer and starting polymer), styrene (second polymer) and isoprene or butadiene (third polymer). The microstructure of the polymer chains was examined using dual-detection size-exclusion chromatography, and the nanostructure of the materials was investigated by differential scanning calorimetry and solid-state nuclear magnetic resonance. Reactions were always slow (although faster than the corresponding processes in solution), and exhibited limited reinitiation by isoprene when in emulsion. The materials containing isoprene exhibit a nanostructure with a phase separation into high-T_g polystyrene-rich domains and low-T_g polyisoprene-rich domains, revealed by DSC and NMR. This has the potential to lead to barrier materials with novel physical properties.     

Asymmetric synthesis of the cis- and trans-stereoisomers of 4-aminopyrrolidine-3-carboxylic acid and 4-aminotetrahydrofuran-3-carboxylic acid

The diastereoselective conjugate addition of lithium (S)-N-benzyl-N-[small alpha]-methylbenzylamide has been successfully applied to the first asymmetric syntheses of cis-(3S,4R)- and trans-(3R,4R)-4-aminotetrahydrofuran-3-carboxylic acids (26% and 25% overall yield respectively, >98% d.e. and >97% e.e. in each case). Furthermore, the most efficient asymmetric synthesis to date of cis-(3R,4R)- and trans-(3R,4S)-4-aminopyrrolidine carboxylic acids is delineated: for cis-(3R,4R), four steps, >98% d.e., 52% overall yield; for trans-(3R,4S), five steps, >98% d.e., 50% overall yield.     

Asymmetric polymerization using C1 resources

Two examples of asymmetric alternating copolymerization, (1) the alternating copolymerization of α‐olefins (monosubstituted ethenes) with carbon monoxide and (2) the alternating copolymerization of meso‐epoxide with carbon dioxide, are described, and the meaning of chirality in polymer synthesis is emphasized. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 215–221, 2004     

Synthesis of 1-aminocyclopropane-1-carboxylic acid

A three-stage method of synthesizing the natural plant growth regulator 1-aminocyclopropane-l-carboxylic acid by the interaction of cyanoacetic ester with 1,2-dibromoethane has been studied.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89 14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 855—857, November-December, 1995. Original article submitted November 28, 1994.     

Asymmetric synthesis of 2-amino-3-hydroxynorbornene-2-carboxylic acid derivatives

The enantioselective synthesis of 2-amino-3-hydroxynorbornene-2-carboxylic acid derivatives (5) was studied using the Diels-Alder reaction between cyclopentadiene and different dienophiles, i.e., alkyl 5-oxo-2-phenyloxazol-4-methylenecarbonates (1) or 2-benzoylamino-3-alkoxycarbonyloxy-acrylates (12), operating with different Lewis acids and both with thermal and with ultrasound conditions. The enantioselective synthesis of the exo/endo compounds 5c,d and 5'c,d was achieved starting from the chiral menthyl acrylates 12b,c using Mg(ClO(4))(2) as the catalyst and ultrasound. The cycloadducts were obtained in very good yield, in mild conditions, in short time, and in good diastereomeric excess (exo, 80%; endo, 87%). Finally, the use of alkylidene-oxazolones or acrylates and EtAlCl(2) or Mg(ClO(4))(2) as the catalyst allowed control of the cycloaddition reaction in favor of the exo or endo products.     

Electroinitiated polymerization of butadiene sulfone

Electroinitiated polymerization of butadiene sulfone was achieved by direct electron transfer in acetonitrile—tetrabutylammonium fluoroborate system by controlled potential electrolysis technique. High conversions were obtained at reasonable temperatures and polymerization times. The polymer was found to be composed of linear segments along with some cyclic units. The effect of monomer concentration, temperature, and polymerization potential on the rate of polymerization was investigated. Temperature and polymerization potential have positive effects on the rate of polymerization. The effect of ultrasonic vibration was also investigated by conducting electrolyses at different monomer concentrations in the presence and absence of ultrasonic vibration. It was observed that the rate of polymerization increases significantly in the presence of ultrasonic vibration. The inverse relationship between the rate of polymerization and monomer concentration was observed in presence and absence of ultrasonic vibration.     

Transformations of pyrrolanthrone-1-carboxylic acid

The preparative possibilities of syntheses based on pyrrolanthrone-1-carboxylic acid were studied. Methylation of the acid or its ester leads to N-methylpyrrolanthrone-1-carboxylic acid esters. The esters were converted to amides and hydrazides, and the latter were converted to 1-amino derivatives through the azides. The indicated transformations and decarboxylation in phosphoric acid give the products in high yields.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 785–788, June, 1978.     

Asymmetric synthesis of substituted 1-aminocyclopropane-1-carboxylic acids via diketopiperazine methodology

Diketopiperazinespirocyclopropane 12 is prepared in > 98% d.e. via the conjugate addition of a phosphorus ylide to (6S)-N,N'-bis(p-methoxybenzyl)-3-methylenepiperazine-2,5-dione 2. Deprotection and hydrolysis of adduct 12 and subsequent peptide coupling demonstrate the applicability of this methodology to the asymmetric synthesis of 1-aminocyclopropane-1-carboxylic acids for incorporation into novel peptides. A model for the high level of diastereofacial selectivity observed in the cyclopropanation reaction is presented. A highly selective asymmetric approach (> 98% d.e.) to (S)-[2,2-(2)H2]-1-aminocyclopropane-1-carboxylic acid 29 is also reported via a deuterated sulfur ylide addition to acceptor 2.     

Derivatives of 1-hydroxytetrazole-5-carboxylic acid

Conclusions We have developed a method for obtaining ethyl 1-hydroxytetrazole-5-carboxylate from ethoxycarbonylchloroaldoxime. Various derivatives of 1-hydroxytetrazole-5-earboxylic acid have been obtained.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2540–2543, November, 1987.     

Anionic polymerization of a fluorinated butadiene

1,1-Bis(trifluoromethyl)-1,3-butadiene (I) is cleanly prepared in three steps. I produces an amorphous polymer by free-radical catalysis. Crystalline poly-I is produced by butyllithium catalysis in tetrahydrofuran at ?78°C. Qualitative kinetic experiments indicate that the anionic polymerization proceeds by a “living polymer” process. An AB block copolymer may be formed by adding I to anionically propagating butadiene; however, the reverse does not occur.     

Tetrathiophosphoric acid tri(1-phenylethyl) ester and1-phenylethyl-diphenylphosphinodithioate as controlled radical polymerization agents

Polystyrene and polystyrene-b-polyvinylacetate have been prepared in presence of either tetrathiophosphoric acidtri(1-phenylethyl) ester 1 or 1-phenylethyl-diphenylphosphinodithioate 2 under radical conditions. From kinetic studies performed with or without 1 or 2, it was shown that the polymerization presents the criteria of living/controlled polymerization.     

Asymmetric anionic polymerization of optically active N-1-cyclohexylethylmaleimide

Chiral (S)-(−)-N-1-cyclohexylethylmaleimide [(S)-CEMI] and (R)-(+)-N-1-cyclohexylethylmaleimide [(R)-CEMI] were synthesized successfully and then polymerized with chiral complexes of (−)-sparteine or (S,S)-(1-ethylpropylidene)bis(4-benzyl-2-oxazoline) [(S,S)-Bnbox] and organometal as initiators in toluene or tetrahydrofuran to obtain optically active polymers. The effects of the polymerization conditions on the optical activity and structure of poly(N-1-cyclohexylethylmaleimide)s were investigated with gel permeation chromatography, circular dichroism, specific rotation, and ¹³C NMR measurements. Poly[(R)-CEMI] obtained with dimethylzinc (Me₂Zn)/(S,S)-Bnbox had the highest specific rotation ([α]₄₃₅ = +323.7°). Complexes of Bnbox and diethylzinc or Me₂Zn were used very effectively as chiral initiators for the asymmetric anionic polymerization of (S)-CEMI and (R)-CEMI. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4682–4692, 2004