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Maheswara, Muchchintala,Oh, Sang-Hyun,Kim, Ke-Tack,Do, Jung-Yun Korean Chemical Society 2008 Bulletin of the Korean Chemical Society Vol.29 No.9
A simple and efficient synthesis of 3,4-dihydropyrimidinones or thiones is described, using silica-supported perchloric acid ($HClO_4-SiO_2$) as a heterogeneous catalyst from an aldehyde, $\beta$-dicarbonyl compound, and urea or thiourea under solvent-free conditions. Compared to the classical Biginelli reactions, this method consistently has the advantage of high yields, short reaction time, easy separation, and tolerance towards various functional groups.
실리콘, 게르마늄, 주석이 결합된 고굴절를 아크릴 고분자의 합성
마해스와라(Muchchintala Maheswara),도정윤(Jung Yun Do) 한국고분자학회 2010 폴리머 Vol.34 No.6
실리콘, 게르마늄, 주석이 결합된 7개의 아크릴 단량체가 개발되었고 이를 광경화시킨 필름의 굴절률을 측정하였다. 공단량체로 가교도가 높은 triacrylate(Trimer)를 사용하여 형성된 공중합체의 굴절률로부터 단일중합체의 굴절률을 계산하였다. 공유 결합된 Ph3Si, Ph3Ge, Ph3Sn은 각각 아크릴 고분자 필름의 굴절률을 향상시키는데 기여하였고 주석이 게르마늄에 비해 약간 높은 기여도로 나타났다. 주석에 의한 굴절률 향상 효과는 Bu3Sn을 도입한 결과와 aliphatic acrylate의 비교로 보다 명확하게 입증되었다. 주석과 황의 안정된 결합을 이용하여 Ph3SnS가 도입된 아크릴 고분자의 굴절률은 589 nm에서 1.671로 높게 측정되었다. 측정 파장으로 656, 830, 1310, 1550 nm에서도 비슷한 굴절률이 관찰되었다. New seven acrylic monomers with covalently bonded silicon, germanium, and tin were prepared for high refractive index materials. The monomers were copolymerized with a cross-linkable comonomer (Trimer) to prepare UV-films for optical characterization. The refractive index of the copolymers increased in proportion to the monomer content and extrapolated to determine that of homopolymer. Ph3Si, Ph3Ge, and Ph3Sn groups contributed to increase the refractive index of acrylic polymer, in which Ph3Sn was more effective than Ph3Ge. The index increment confidently occurred with Bu3Sn attachment in comparison with aliphatic acrylic polymers. Ph3SnS-attached acrylate polymer showed a refractive index of 1.671 at 589 nm. The index change was similarly observed at various different wavelengths (656, 830, 1310, and 1550 nm).
n-Propyl fluoroformate, Addition-elimination, Grunwald-Winstein equation, Leaving group effect
도정윤,Muchchintala Maheswara,Sang Hyun Oh,Ketack Kim,Jung Yun Do 대한화학회 2008 Bulletin of the Korean Chemical Society Vol.29 No.9
A simple and efficient synthesis of 3,4-dihydropyrimidinones or thiones is described, using silica-supported perchloric acid (HClO4-SiO2) as a heterogeneous catalyst from an aldehyde, β-dicarbonyl compound, and urea or thiourea under solvent-free conditions. Compared to the classical Biginelli reactions, this method consistently has the advantage of high yields, short reaction time, easy separation, and tolerance towards various functional groups.
Novel Synthesis of Hydrophilic Dipolar Chromophores using Dendronized Sulfonates
Mi Rae Kim,Muchchintala Maheswara,도정윤 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.2
A series of hydrophilic chromophores was synthesized through introduction of dendritic sulfonate anions using click chemistry. A dendron structure bearing several sulfonate groups enhances hydrophilicity of attached chromophores. A click triazole formation connects chromophores with hydrophilic groups. A neutral trichloroethyl sulfonate has versatile features such as easy introduction, chemical endurance for isolation or storage, and convenient transformation to a hydrophilic anion. Zinc and OH mediated cleavage of trichloroethyl group from the neutral sulfonate undergoes to generate a water-soluble sulfonate anion. The solubility was examined with different counter cations and in different pH media and thus increased with the number of attached sulfonate ion. Two hydrophilic chromophores of stilbene-derived and azobenzene-derived dipolar structures exhibit clear negative and positive solvatochromism in protic solvents, respectively.
Novel Synthesis of Hydrophilic Dipolar Chromophores using Dendronized Sulfonates
Kim, Mi-Rae,Maheswara, Muchchintala,Do, Jung-Yun Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.2
A series of hydrophilic chromophores was synthesized through introduction of dendritic sulfonate anions using click chemistry. A dendron structure bearing several sulfonate groups enhances hydrophilicity of attached chromophores. A click triazole formation connects chromophores with hydrophilic groups. A neutral trichloroethyl sulfonate has versatile features such as easy introduction, chemical endurance for isolation or storage, and convenient transformation to a hydrophilic anion. Zinc and OH mediated cleavage of trichloroethyl group from the neutral sulfonate undergoes to generate a water-soluble sulfonate anion. The solubility was examined with different counter cations and in different pH media and thus increased with the number of attached sulfonate ion. Two hydrophilic chromophores of stilbene-derived and azobenzene-derived dipolar structures exhibit clear negative and positive solvatochromism in protic solvents, respectively.
Ji-myoung Ye,Muchchintala Maheswara,도정윤 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.8
Preparation of several new spirocyclic mercapto derivatives is described. Thiol protection on multi-carbonyl compounds allows of high sulfur content necessary to induce high refractive index. Condensation of 1,3- dimercapto-2-propanol and cyclohexanone followed by successive oxidation and thioacetalization affords a dispirocycle with four sulfurs. Selective S,S-protection of cyclohexane-1,4-dione is achieved with 1,3- dimercapto-2-propanol and 2,3-dimercapto-1-propanol to provide dispirocycles with four sulfurs. Olefineoxidation of norbornene gives a useful dialdehyde intermediate which is transformed to 1,3-dithiolane for a linearly-bound-cyclic molecule. Refractive index of linearly-bound-cycles was below 1.60 and dispirocycles exhibited high refractive index of 1.57-1.69.