Development of TfOH-Catalyzed Spirocyclization by Intramolecular Friedel-Crafts-type 1,4-Addition: Application to the Total Synthesis of the Unusual Proaporphine Alkaloid (±)-Misrametine

An effective method was developed for TfOH-catalyzed construction of spiroindanes and spirotetralines containing an all-carbon quaternary stereocenter. Intramolecular Friedel-Crafts-type 1,4-addition of the substrates which were di- or trimethoxybenzene and 2-cyclohexenone linked by an alkyl chain proceeded smoothly in the presence of 30 mol % of TfOH. A variety of spiroindanes and spirotetralines were obtained with moderate to excellent yield by this method. The reaction was successfully applied in the first total synthesis of the unusual proaporphine alkaloid (±)-misrametine, which included the gram-scale spirocyclization and selective O-demethylation used KCN in DMSO condition as key steps.     

Synthesis of biocompatible and biodegradable block copolymers of polyvinyl alcohol‐block‐poly(ε‐caprolactone) using metal‐free living cationic polymerization

Applications of metal‐free living cationic polymerization of vinyl ethers using HCl · Et₂O are reported. Product of poly(vinyl ether)s possessing functional end groups such as hydroxyethyl groups with predicted molecular weights was used as a macroinitiator in activated monomer cationic polymerization of ε‐caprolactone (CL) with HCl · Et₂O as a ring‐opening polymerization. This combination method is a metal‐free polymerization using HCl · Et₂O. The formation of poly(isobutyl vinyl ether)‐b‐poly(ε‐caprolactone) (PIBVE‐b‐PCL) and poly(tert‐butyl vinyl ether)‐b‐poly(ε‐caprolactone) (PTBVE‐b‐PCL) from two vinyl ethers and CL was successful. Therefore, we synthesized novel amphiphilic, biocompatible, and biodegradable block copolymers comprised polyvinyl alcohol and PCL, namely PVA‐b‐PCL by transformation of acid hydrolysis of tert‐butoxy moiety of PTBVE in PTBVE‐b‐PCL. The synthesized copolymers showed well‐defined structure and narrow molecular weight distribution. The structure of resulting block copolymers was confirmed by ¹H NMR, size exclusion chromatography, and differential scanning calorimetry. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5169–5179, 2009     

Efficient resolution of 2,2′-dihydroxy-1,1′-binaphthalene-4,4′- and 6,6′-dicarboxylic acid by complexation with cinchonidine and brucine

2,2′-Dihydroxy-1,1′-binaphthalene-4,4′- and 6,6′-dicarboxylic acid were resolved efficiently by complexation with cinchonidine and brucine, respectively. The absolute configurations of these compounds were determined by X-ray crystallographic analyses.     

Synthesis of highly refractive polyimides derived from 3,6‐bis(4‐aminophenylenesulfanyl)pyridazine and 4,6‐bis(4‐aminophenylenesulfanyl)pyrimidine

A series of aromatic polyimides (PIs) containing pyridazine or pyrimidine in their main chains has been developed. All of the PIs were prepared from newly synthesized diamines, 3,6‐bis(4‐aminophenylenesulfanyl)pyridazine (APP), 4,6‐bis(4‐aminophenylenesulfanyl)pyrimidine (APPM) and aromatic dianhydrides, 4,4′‐[p‐thiobis(phenylenesulfanyl)]diphthalic anhydride (3SDEA) and 4,4′‐oxydiphthalic anhydride (ODPA) via the conventional two‐step polycondensation. The PIs showed good thermal stability with 10% weight loss at temperatures above 450 °C and glass transition temperatures above 190 °C. Films with a 10‐μm thickness exhibited good optical transparency above 80% at 500 nm, high refractive indices ranging from 1.7218 to 1.7499, and low birefringence between 0.0066 and 0.0102. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4886–4984, 2009     

A Periodic Mesoporous Organosilica‐Based Donor–Acceptor System for Photocatalytic Hydrogen Evolution

A new solid‐sate donor–acceptor system based on periodic mesoporous organosilica (PMO) has been constructed. Viologen (Vio) was covalently attached to the framework of a biphenyl (Bp)‐bridged PMO. The diffuse reflectance spectrum showed the formation of charge‐transfer (CT) complexes of Bp in the framework with Vio in the mesochannels. The transient absorption spectra upon excitation of the CT complexes displayed two absorption bands due to radical cations of Bp and Vio species, which indicated electron transfer from Bp to Vio. The absorption bands slowly decayed with a half‐decay period of approximately 10 μs but maintained the spectral shape, thereby suggesting persistent charge separation followed by recombination. To utilize the charge separation for photocatalysis, Vio–Bp–PMO was loaded with platinum and its photocatalytic performance was tested. The catalyst successfully evolved hydrogen with excitation of the CT complexes in the presence of a sacrificial agent. In contrast, reference catalysts without either Bp–PMO or Vio gave no or little hydrogen generation, respectively. In addition, a homogeneous solution system of Bp molecules, methylviologen, and colloidal platinum also evolved no hydrogen, possibly due to a weaker electron‐donating feature of molecular Bp than that of densely packed Bp in Bp–PMO. These results indicated that densely packed Bp and Vio are essential for hydrogen evolution in this system and demonstrated the potential of PMO as the basis for donor–acceptor systems suitable for photocatalysis.     

Synthesis and characterization of organosoluble ditrifluoromethylated aromatic polyimides

Two novel diamine monomers, 1,4‐bis (4‐aminophenoxy)‐2‐[(3′,5′‐ditrifluoromethyl)phenyl]benzene and 1,4‐bis [2′‐cyano‐3′(4″‐amino phenoxy)phenoxy]‐2‐[(3′,5′‐ditrifluoromethyl)phenyl] benzene, were synthesized from (3,5‐ditrifluoromethyl)phenylhydroquinone. A series of ditrifluoromethylated aromatic polyimides derived from the diamines were prepared through a typical two‐step polymerization method. These polyimides had a high thermal stability, and the temperatures at 10% weight loss were above 507 °C in nitrogen. Most of the polymers showed good solubility in anhydrated 1‐methyl‐2‐pyrrolidone, N,N‐dimethylacetamide, N,N‐dimethylformamide, chloroform, and tetrahydrofuran at room temperature. All the polymers formed transparent, strong, and flexible films with tensile strengths of 63.6–95.8 MPa, elongations at break of 5–10%, and Young's moduli of 2.38–2.96 GPa. The dielectric constants estimated from the average refractive indices are 2.69–2.89. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3018–3029, 2005     

The relationship between the structures of semi-rigid homo- and copolyesters based on 5,5'-diphenyl-2,2'-bis(1,3,4-thiadiazole)s and their liquid crystalline and optical properties

New semi-rigid homo- and copolyesters composed of the quaterphenyl analogue of 2,2'-bis(1,3,4-thiadiazole) (BTD), 5,5'-diphenyl-2,2'-bis(1,3,4-thiadiazole) (DBTD), were prepared by high temprature solution polycondensation of monomers, 3,3'- and 4,4'-dioxydiundecanol derivatives of DBTD with four dimethyl esters, and their liquid crystalline (LC) and optical properties were investigated. DSC measurements, texture observations using a polarizing microscope equipped with a hot stage, and powder X-ray diffraction showed that the homopolymers containing the 4,4'-DBTD unit form more stable LC phases than those having the 3,3'-DBTD unit. The 4,4'-DBTD-containing polymers and the 3,3'-DBTD unit-poor copolymers, except for the 3,3'-DBTD unit-rich copolymers and the 3,3'-DBTD-containing homopolymers (which formed highly ordered smectic or crystal mesophases), displayed a thermotropic LC smectic C phase. Solution and solid state UV-vis and photoluminescent (PL) spectra showed that the polyesters display miximum absorbances and bluish-green or blue emission based on the DBTD unit, where the Stokes shifts were observed. The peak positions in the UV-vis and the PL spectra of homopolymers composed of the 4,4'-DBTD unit were at higher wavelengths than those in the corresponding 3,3'-DBTD-containing homopolymers, due to its more conjugated structure. In the copolymers the peak maxima were shifted to shorter wavelengths with the increase of 3,3'-DBTD content.