Yong-Jin Yoon

Efficient cleavage of terminal acetonide group: Chirospecific synthesis of 2,5-dideoxy-2,5-imino-D-mannitol

Abstract Dowex 50W-X8 was efficient catalyst for selective cleavage of terminal actonide including acid-sensitive multifunctional groups. A facile and economically synthesis of DMDP (2,5-dideoxy-2,5-imino-D-mannitol) is described via selective hydrolysis and intramolecular nucleophilic amination.

TBAF-assisted copper-catalyzed N-arylation and benzylation of benzazoles with aryl and benzyl halides under the ligand/base/ solvent-free conditions.

TBAF-assisted N-arylation and benzylation of benzazoles such as 1H-benzimidazole, 1H-indole, and 1H-benzotriazole with aryl and benzyl halides have been demonstrated under the ligand/base/solvent-free conditions. In the presence of CuBr2 and TBAF (n-Bu4NF), the azoles underwent N-arylation and benzylation with aryl and benzyl halides smoothly in moderate to good yields. It is noteworthy that the reaction is conducted under the ligand/base/solvent-free conditions.

Conversion of Oximes to Carbonyl Compounds with 2-Nitro-4,5-dichloropyridazin-3(2H)-one

Conversion of oximes to the carbonyl compounds has been demonstrated with use of 2-nitro-4,5-dichloropyridazin-3(2H)-one (2) under microwave irradiated conditions. Fourteen aliphatic and aromatic oximes converted to their corresponding aldehydes and ketones in good to excellent yields. It is noteworthy that the reaction is conducted under neutral, mild, and eco-friendly condition.

Regioselectivity of Pictet–Spengler cyclization: synthesis of halotetrahydroisoquinolines

Abstract The regioselectivity of the Pictet–Spengler cyclization for the synthesis of isoquinolines depends on the aryl substituent at C-2. The ratio of halotetrahydroisoquinoline 4 to isoquinoline 3 increases with increasing electrophilicity of the aromatic ring (H≪I

ZnCl2‐Mediated Synthesis of Carboxylic Anhydrides using 2‐Acyl‐4,5‐dichloropyridazin‐3(2H)‐ones

Abstract ZnCl2 is an efficient catalyst for synthesis of carboxylic acid anhydride from 2‐acyl‐4,5‐dichloropyridazin‐3(2H)‐ones. Treatment of 2‐acyl‐4,5‐dichloropyridazin‐3(2H) ‐ones with ZnCl2 (0.5 equivalents) and air in refluxing dry THF or acetonitrile gave the corresponding symmetric acid anhydrides in good to excellent yield.

Convenient Preparation of O‐Alkylhydroxamic Acids Using 2‐Acylpyridazin‐3(2H)‐ones

Abstract Treatment of O‐alkylhydroxylamine hydrochlorides with 2‐acyl‐4,5‐dichloropyridazin‐3(2H)‐ones in the presence of triethylamine or Amberlite® IRA‐67 in acetonitrile gave corresponding O‐alkylhydroxamic acid derivatives in excellent yields. This is an efficient, convenient, and eco‐friendly method.

Fabrication and Characterization of Dye-Sensitized Solar Cells for Greenhouse Application

We have developed dye-sensitized solar cells using novel sensitizers with enhanced transmittance of red (625–675 nm) and blue (425–475 nm) wavebands to control the illumination condition in the greenhouse. Novel ruthenium bipyridyl sensitizers with general formulas (Me3PhN)4[Ru(dcbpy)2(NCS)2] (JJ-7) and (Me3BnN)4[Ru(dcbpy)2(NCS)2] (JJ-9) have been synthesized and demonstrated as efficient sensitizers in dye-sensitized solar cells for greenhouse application. Under standard AM 1.5 sunlight, the solar cell of JJ-7 using a liquid-based electrolyte exhibits a short-circuit photocurrent density of 8.49 mA/cm2, an open-circuit voltage of 0.83 V, and a fill factor of 0.71, corresponding to an overall conversion efficiency of 4.96% on 5 m TiO2 film. The transmittance of JJ-7 and JJ-9 shows 62.0% and 61.0% at 660 nm and 18.0% and 15.0% at 440 nm for cultivation on 5 m TiO2 film, respectively.

Chemoselective reduction of highly-functionalized azidopyridazines to corresponding aminopyridazines using FeNH4Cl in organic solvent-water two-phase solution

Abstract Highly functionalized azidopyridazines can be reduced chemoselectively to the corresponding amines in excellent yields.

Simple synthesis of (–)-deoxymannojirimycin and (2S,3R,4R,5R)-3,4,5-trihydroxypipecolic acid via regioselective hydrolysis

A short and efficient synthesis of (–)-deoxymannojirimycin and (2S,3R,4R,5R)-3,4,5-trihydroxypipecolic acid is described with D-glucono-δ-lactone as chiral educt. Key transformations included selective cleavage of a terminal isopropylidene group with Dowex 50W-X8 (H+) and intramolecular nucleophilic amination.

Fluorescent 2-styrylpyridazin-3(2H)-one derivatives as probes targeting amyloid-beta plaques in Alzheimer's disease.

Amyloid plaques, which are primarily composed of aggregated amyloid-beta (Aβ) peptide, are the neuropathological hallmarks of Alzheimers disease (AD). Fluorescent markers containing 2-styrylpyridazin-3(2H)-ones were developed to detect intracellular aggregated Aβ peptides. Nine compounds exhibited a greater than 10-fold increase of in emission spectra before and after mixing with Aβ aggregates compared with before mixing. Among these compounds, compound 9n exhibited the highest affinity for Aβ aggregates (K(d)=1.84 μM) and selectively stained both aggregated intracellular Aβ and Aβ plaques in the transgenic AD model mice (APP/PS1). These preliminary results indicate that 2-styrylpyridazin-3(2H)-one derivatives are promising alternative fluorescence imaging agent for the study of AD.