Preparation of multiallylic dendronized polymers via anionic polymerization (original) (raw)
Related papers
Journal of the American Chemical Society, 2008
Materials. All chemicals (>98% purities) were purchased from Aldrich and used as received unless otherwise stated. Benzene for polymerizations was dried and distilled twice over CaH 2 and polystyryl lithium successively. THF was purified by distillation over CaH 2 and then from a purple Na/benzophenone solution. Tetramethylethylene diamine (TMEDA) (Aldrich, 99%) was sodium-dried and distilled. Solutions of sec-Butyllithium (s-BuLi) (Aldrich) were used for halogen-lithium exchange reaction after double titration. 26 The diphenylmethylpotassium (DPMK) solution was prepared and titrated following procedures described elsewhere. 27 Styrene (S) (Aldrich, 99%) was dried and distilled twice over CaH 2 and dibutyl magnesium successively. Butadiene (B) (Aldrich, 99%) was stirred over s-BuLi at-30°C for 2 h and distilled prior to use. Ethylene oxide (EO) (Fluka, 99.8%) was stirred over sodium for 3 h at-40 °C and then distilled before use. For the synthesis of the tetrabromoinitiator, we followed the procedure described by Wolfe and al. 28 Measurements. High-purity argon (>99.5%) was rigorously dried and deoxygenated
Journal of Polymer Science Part A: Polymer Chemistry, 2005
1,1,1-Tris(4-trimethylsiloxyphenyl)ethane, (silylated THPE), was polycondensed with 2,4-difluoroacetophenone and 2,4-difluorobenzophenone. All polycondensations were performed in N-methylpyrrolidone with K 2 CO 3 as promotor. The feed ratio THPE/difluoroaromat was varied from 1.0:1.3 to 1.0:1.5. Instead of hyperbranched polymers or gels, soluble multicyclic oligo-and polyethers were identified as main reaction products by MALDI-TOF mass spectrometry in all experiments. At feed ratios around 1.0:1.5 multicycles free of functional group were the main products. However, when isomeric a 2 -monomers such as 2,6-difluoroacetophenone, 2,6-difluorobenzophenone (or 2,6-difluorodiphenylsulfone) were used, gelation occurred at feed ratios as low as 1.0:1.1. An explanation of the different cyclization tendencies on the basis of different conformations is discussed. V V C 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6233-6246, 2005
Syntheses of Special Monomers forπ-Conjugated Polymers
Macromolecular Symposia, 2008
Tailored monomers based on the activated esters of 2,5-dibromo-benzoic and 2,5-dibromobenzene-1-sulfonic acids or 3-substituted 2,5-dibromothiophene suitable for the Suzuki, Yamamoto or Grignard metathesis (GRIM) coupling reactions were synthesized and characterized by the melting point, elemental analysis, 1 H NMR, FT IR, and TLC. The Horner-Wadsworth-Emmons reaction was utilized for the preparation of 3-(arylvinyl)-2,5-dibromothiophenes and the 4-nitrophenol or Nhydroxysuccinimide for the preparation of activated esters. A monomer with b-diketone active structure was prepared and characterized as well.
Organic Letters, 2011
Preparation of starting materials 3 Representative procedure for the cyclization of polyenes 4 Analytical and spectral data of cyclized compounds 4.1 Crystallographic structure for dimethyl 4,4,8,9a-tetramethyl-1,2,3,4a,5,9-hexahydro-1Hbenzo[7]annulene-6,6-dicarboxylate (5b), single diastereoisomer (trans) 4.2 Crystallographic structure for ethyl 9-cyano-1,1,4a-trimethyl-1,2,3,4,4a,9,10,10aoctahydrophenanthrene-9-carboxylate (8b), major diastereoisomer (2 rotamers) 4.3 Crystallographic structure for diethyl 3,3,6a-trimethyl-1,2,3a,3a 1 ,4,6,7,11b-octahydro-1Hbenzo[de]anthracene-5,5-dicarboxylate (9b), single diastereoisomer S-2 1 General information 1 H NMR and 13 C NMR spectra were recorded on a BRUKER AC 200 and BRUKER AVANCE 500. 1 H NMR spectra are described as follows: chemical shift in ppm (δ) relative to TMS at 0 ppm. Integration, multiplicity (s = singlet, d = doublet, t = triplet, q = quadruplet, p = pentuplet, m = multiplet and b = broad), and coupling constants (Hz). 13 C NMR spectra chemical shifts are reported in ppm (δ) relative to CDCl 3 at 77.16 ppm. High-resolution mass spectra were obtained on a LTQ-Orbitrap hybrid mass spectrometer. Column chromatography was carried out on silica gel (spherical, neutral, 63-200 um, Geduran Si 60, Merck KGaA). GC analyses were performed with a Varian 3380 chromatograph equipped with a VF-5ms capillary column (thickness: 0.25 mm, length: 25 m, inside diameter: 0.25 mm). GC/MS analyses were performed with a Shimadzu QP2010S-MS chromatograph (EI, 70 eV) equipped with a SLB-5ms capillary column (thickness: 0.25 mm, length: 30 m, inside diameter: 0.25 mm). Analytical thin-layer chromatography (TLC) was performed on 0.2 mm precoated plate Kieselgel 60 F 254 (Merck). Structures of the products were determined by 1D, 2D, DEPT, COSY, HMBC, HMQC, NOESY experiments. Structures of compounds 5b, 8b and 9b were confirmed by X-Ray crystallography analysis, performed on Bruker-Nonius X-ray diffractiometer. The melting points (°K) of compounds 5b, 8b and 9b were performed with an Electrothermal 9100. All compounds of this study are racemic molecules. Materials. Dichloromethane, diméthylformamide (DMF), nitromethane and tetrahydrofurane (THF) were dried and/or distilled according to conventional procedures. 1 Bi(OTf) 3 , NaH, K 2 CO 3 were purchased (Aldrich) and used as received. 2 Preparation of starting materials Preparation of compounds 1a, 3a and 4a Typical procedure: preparation of (E)-diethyl 2-[3,7-dimethylocta-2,6-dienyl]malonate. To a solution of K 2 CO 3 in DMF (0.5 M), diethylmalonate (30 mmol) and geranylbromide (1.1 equiv.) were added under an inert atmosphere at room temperature and left to stir overnight. The reaction mixture was quenched using a 1 M aqueous HCl solution. The aqueous layer was then extracted with diethyl ether (three times). The combined organic layers were then washed with a 0.1 M aqueous HCl solution, water and then brine, dried over MgSO 4 , and evaporated under vacuum. Silica gel flash column chromatography was performed on the crude product using a mixture pentane/ethyl acetate as the eluent yielding in a colorless oil (91%).
Functionalized Carbosilane Dendritic Species as Soluble Supports in Organic Synthesis
The Journal of Organic Chemistry, 2000
A new methodology, which is compatible with the use of reactive organometallic reagents, has been developed for the use of carbosilane dendrimers as soluble supports in organic synthesis. Hydroxy-functionalized dendritic carbosilanes Si[CH 2 CH 2 CH 2 SiMe 2 (C 6 H 4 CH(R)OH)] 4 (G 0 -OH, R ) H or (S)-Me) and Si[CH 2 CH 2 CH 2 Si[CH 2 CH 2 CH 2 SiMe 2 (C 6 H 4 CH(R)OH)] 3 ] 4 (G 1 -OH, R ) H or (S)-Me) were prepared and subsequently converted into the esters Si[CH 2 CH 2 CH 2 SiMe 2 (C 6 H 4 -CH(R)OC(O)CH 2 Ph)] 4 (R ) H or (S)-Me) and Si[CH 2 CH 2 CH 2 Si[CH 2 CH 2 CH 2 SiMe 2 (C 6 H 4 CH(R)OC-(O)CH 2 C 6 H 4 R′)] 3 ] 4 (R ) H and R′ ) H or R ) (S)-Me and R′ ) H or R ) H and R′ ) Br). As an example the latter compound was functionalized under Suzuki conditions. The functionalized carboxylic acid was obtained in high yield after cleavage from the dendritic support. Moreover, the ester functionalized dendrimers were converted to the corresponding zinc enolates followed by a condensation reaction with an imine to a -lactam in excellent yield and purity. Furthermore, it was demonstrated that a small combinatorial library of -lactams could be prepared starting from a carbosilane dendrimer functionalized with different ester moieties. These results show that carbosilane dendrimers can be applied as soluble substrate carriers for the generation of low molecular weight organic molecules. In combination with nanofiltration techniques, separation and recycling of the dendrimers can be realized. Di Girolamo, M.; Raspolli Galletti, A. M.; Sbrana, G.; Brunelli, M.; Bertolini, G.