• Bulletin of the Korean Chemical Society
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• 제35권7호
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• pp.1970-1972
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• 2014

A facile and efficient synthesis of dronedarone hydrochloride starting from commercially available 4-nitrophenol is described. This approach features a tandem-type synthesis of 3-carbonylated benzofuran involving cyclization of 2-ethynylphenol followed by $CO_2$ fixation at the 3-position of the benzofuran ring mediated by potassium carbonate without the addition of any transition metal catalyst.

• Bulletin of the Korean Chemical Society
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• 제16권11호
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• pp.1060-1064
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• 1995

The reactivity of superoxide ion (O2-.) with halogenated substrates is investigated by cyclic voltammetry and rotated ring-disk electrode method in aprotic solvents. The more positive the reduction potential of the substituted nitrile, the more facile is nucleophilic displacement by O2-.. The reaction rates of halogenonitriles with O2-. vary according to the leaving-group propensity of halide (Br > Cl > F). The relative reaction rates of other substituted nitriles are in the order of electron-withdrawing propensity of the substituent group (CN > C(O)NH2 > Ph ≒ CH2CN). The reaction of O2-. with dihalocarbons indicates that five-membered rings can be rapidly formed by the cyclization of substrate and O2-., and the relative rates of cyclization depend on the number of methylenic carbons {Br(CH2)nBr, [n=1 < 2 < 3 > 4 > 5]}. Mechanisms are proposed for the reaction of O2-. with halogenated substrates.

• 대한화학회지
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• 제32권1호
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• pp.71-78
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• 1988

20,21,24,25-Tetranitrodibenzo-18-crown-6에 알코올성 염기를 가하여 친핵성 치환반응을 유도하면 crown ether 화합물을 이루는 polyether 고리가 끊어져서 주생성물로 2,4,5-trialkoxynitrobenzene 유도체, 4,5-dialkoxy-1,2-dinitrobenzene 유도체 그리고 crown ether 고리가 부분적으로 끊어져 생긴 bis[(alkoxynitrophenoxy)ethyl]ether 유도체가 부생성물로 얻어졌다. 이가 알코올성 염기에서는 polyether 고리가 끊어진 생성물과 분자내 치환반응이 다시 진행되어 고리축소 현상이 일어나 12-crown-4의 유도체를 얻게 되거나 출발물질이 도로 생성되었다. 이상의 실험은 다양한 알코올의 농도에서 염기의 종류를 달리하여 그 선택성을 알아보았다.

• Elastomers and Composites
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• 제51권3호
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• pp.195-205
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• 2016

A series of aromatic poly(hydroxyamide)s (PHAs) containing varying oligo(oxyethylene) substituents and 1,3-phenylene imide ring unit in the main chain were synthesized by the direct polycondensation reaction. The inherent viscosities of the PHAs exhibited in the range of 0.89~1.12 dL/g in DMAc or DMAc/LiCl solution. The PH-2~5 copolymers were easily soluble in strong aprotic solvents: DMAc, NMP, DMSO etc. and the PH-5 copolymer was soluble in less polar solvents such as m-creasol and pyridine with LiCl salt on heating. However, all PBOs were quite insoluble in other solvents, but only partially soluble in sulfuric acid. All copolymers (PH-2~5) could afford the flexible and tough films by solution casting. We identified that the PHAs were converted to the PBOs by the thermal cyclization reaction in the range of $200{\sim}380^{\circ}C$. The 10% weight loss temperatures and char yields of the PBOs were recorded in the range of $382{\sim}647^{\circ}C$ and 38.7~73.1% values at $900^{\circ}C$. The tensile strength and initial modulus of the PH-5 in the copolmers showed the highest values of 2.46 GPa and 49.55 MPa, respectively. The LOI values of the PHAs were in the range 26.6~29.0%, and increased with increasing 1,3-phenylene imide ring unit.

• Bulletin of the Korean Chemical Society
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• 제19권3호
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• pp.308-313
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• 1998

A thermally irreversible photochromic system, 2,3-bis(2,4,5-trimethyl-3-thienyl)maleic anhydride (MTMA), has been studied by semi-empirical molecular orbital methods. There are one pair of stable conformations for the closed-ring form and three pairs for the open-ring form, each pair consisting of two mirror-image conformations. Interconversion between the parallel and anti-parallel conformations of the open-ring form is restricted due to high energy barriers. Only the anti-parallel conformation appears to be responsible for photochromic cyclization. Thermostability of the compound is attributed to an avoided crossing at high energy in the ground states of the isomers, whereas the photoreactivity can be explained by the mutually connected excited singlet (S1) states of the isomers, forming a double well potential with a low energy barrier. The large solvent effects can be partly explained with the low dipole moment of the anti-parallel conformation of MTMA in the S1 state. The large variation of quantum efficiency suggests that excess vibronic energy can be utilized to provide the activation energy for the photochromic reaction.

• 대한화학회지
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• 제56권3호
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• pp.322-327
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• 2012

Rapid and efficient synthesis of substituted 3-carboxylquinoline derivatives from 4-chloro-3-formylcoumarin and substituted anilines using 30% $H_2SO_4$ in methanol at room temperature within the duration of 5-30 min., through domino condensation-cyclization-ring opening reaction.

• 대한화학회지
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• 제33권6호
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• pp.644-650
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• 1989

Phthalide sulfone 2와 naphthalenone 6을 만들어서 Hauser-Rhee가 개발한 Michael addition의 새로운 고리 접합법으로 4개의 선형 고리화합물의 구조를 갖는 tetracyclic 화합물 11을 만들었다. 화합물 11의 ring A가 갖고 있는 중요한 이중결합을 이용해서 탄소수가 한 개 증가된 carbomethoxy 화합물 16으로 변형시키는 것은 Arndt-Eistert, Wolff rearrangement를 이용하였다. 그리고 나서 이들을 고리화 반응시킨 뒤 hydroxylation시켜서 최종 생성물인 (${\pm}$)-7-Deoxyaklavinone(18)를 합성하였다.

• 약학회지
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• 제44권6호
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• pp.505-510
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• 2000

The synthesis of pentahydroindanoisoquinoline (4) compound has been achieved via the cyclization of 2-(N-benzylamino)-5,6-difluoro-1-indanol (10a, 10b), which was prepared by condensation and reduction of 2-amino-1-indanol and benzaldehyde in ethanol. The stereochemistry of $H_{6a}$ and $H_{11b}$ of 9,10-difluoro-5,6,6a,7,11b-pentahydroindano[2,1-c]isoquinoline (4) was the trans B/C ring fusion.

• Bulletin of the Korean Chemical Society
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• 제33권1호
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• pp.76-82
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• 2012

A novel and efficient tetrahydrofuranyl ring opening method was developed using the highly reactive TFAT reagent in the presence of an acid scavenger, 2,6-di-tert-butyl-4-methylpyridine. Various acid sensitive groups are compatible with the reaction condition, making it generally applicable to many tetrahydrofuranyl steroids. Moreover, it is a synthetic equivalent of 'Marker degradation' affording an efficient synthesis of C17-OH rockogenin acetate.

• Bulletin of the Korean Chemical Society
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• 제30권6호
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• pp.1331-1336
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• 2009

Photolysis of (2-hydroxyethoxyphenyl)pentamethyldisilane 2 in benzene provides a novel intramolecular cyclization photoproduct 9 which was probably formed from the intramolecular reaction to form a seven-membered ring in silatriene intermediate 7 and then the photochemical disrotatory ring closure of 1,3-butadiene moiety to cyclobutene. Irradiation of 2 in methanol afforded photoproducts 5 and 6 which were formed by the nucleophilic attack of methanol to $\beta$ or $\alpha$ silicon atom in pentamethyldisilanyl group of the photoexcited state of 2. Compounds 10 and 11 were also formed by the same way as in the formation of the photoproducts 5 and 6 in the photolysis of (2-allyloxyethoxyphenyl)pentamethyldisilane 3 in methanol solvent. Photoreaction of (2-acetoxyethoxyphenyl) pentamethyldisilane 4 in methanol gave a photoproduct 12 which was formed via the elimination of dimethylsilylene species in the photoexcited state of 4.