Browsing by Author "Wu, Yen-Ku"

Now showing 1 - 15 of 15

A Combined Tamaru Allylation/Olefin Cross-Metathesis Approach for the Total Syntheses of (+/-)-Paniculidine B, (+/-)-Paniculidine C, and 2-Methylcarbazole
(2018-03-01)
Tseng, Yi-Lun
;
Liang, Min-Chieh
;
Chen, I-Chia
;
Wu, Yen-Ku
;
應用化學系
A concise approach to the total syntheses of racemic paniculidines B and C is described. The route features a combined Tamaru allylation/olefin cross-metathesis sequence for the regiocontrolled synthesis of prenylindole intermediates. In addition, we report a transformation of the prenylated indole into 2-methylcarbazole catalyzed by sulfonic acid-functionalized silica gel.
Electron transfer-induced reduction of organic halides with amines
(2018-06-04)
Fukuyama, Takahide
;
Fujita, Yuki
;
Miyoshi, Hayato
;
Ryu, Ilhyong
;
Kao, Shih-Chieh
Reduction of a variety of organo halides was examined by using amines as a sacrificial hydrogen source. UV light-induced reduction of vinyl and aryl halides with triethylamine proceeded smoothly to give the corresponding reduced products. High temperature heating also caused the reduction and DABCO (1,4-diazabicyclo[2.2.2]octane) also served as a good reducing reagent.
EPR Imaging Spin Probe Trityl Radical OX063: A Method for Its Isolation from Animal Effluent, Redox Chemistry of Its Quinone Methide Oxidation Product, and in Vivo Application in a Mouse
(2016-12)
Serda, Maciej
;
Wu, Yen-Ku
;
Barth, Eugene D.
;
Halpern, Howard J.
;
Rawal, Viresh H.
We report herein a method for the recovery, purification, and application of OX063, a costly, commercially available nontoxic spin probe widely used for electron paramagnetic resonance (EPR) imaging, as well as its corresponding quinone methide (QM) form. This precious probe can be successfully recovered after use in animal model experiments (25-47% recovery from crude lyophilizate with 98.5% purity), even from samples that are >2 years old. Significantly, the recovered trityl can be reused in further animal model EPR imaging experiments. The work also describes support for the observed formation of an air-sensitive radical derived from the QM under reducing conditions.
Formal synthesis of schulzeines B and C: A new route to Gurjar's lactams
(1970-01-01)
Chou, Chu-En
;
Chen, Yi-An
;
Lin, Yi-Ching
;
Kao, Shih-Chieh
;
Chang, Chieh-Yu
Described is a formal synthesis of racemic schulzeines B and C that intercepts intermediates developed by Gurjar and co-workers. The synthetic sequence features an annulative coupling of a ketimine and acrylic acid enabling the construction of the benzoquinolizidine nucleus in a highly convergent manner. We also examined a continuous-flow version of the thermal aza-annulation, which proved less practical as compared to the batch processes.
Intercepting the Nazarov Oxyallyl Intermediate with -Formylvinyl Anion Equivalents to Access Formal Morita-Baylis-Hillman Alkylation Products
(2017-07-01)
Wu, Yen-Ku
;
Lin, Rongrong
;
West, F. G.
;
應用化學系
;
Department of Applied Chemistry
A Lewis acid catalyzed cationic domino reaction involving sequential electrocyclization and polar addition of allenol ethers onto the resulting oxyallyl species is described. The overall sequence allows a highly stereoselective synthesis of densely substituted cyclopentanoid compounds containing -formylvinyl functionality which is formally equivalent to products of a Morita-Baylis-Hillman alkylation process.
Palladium-Catalyzed alpha-Allylation of Secondary Nitroalkanes with Allylic Alcohols and Strategic Exploitation of Seebach's Reagent for the Total Synthesis of (+/-)-Adalinine
(2018-06-01)
Chang, Chieh-Yu
;
Wu, Yen-Ku
;
應用化學系
;
Department of Applied Chemistry
A method is reported for the catalytic direct coupling of allylic alcohols and nitroalkanes. the allylation process, the synergistic action of palladium complexes and titanium(IV) alkoxide facilitates the formation of nitronate and pi-allylpalladium intermediate. In the cases of reluctant allylations, typically with sterically demanding nitroalkanes, we found the addition of substoichiometric amount of DBU greatly facilitates the desired transformation. We also accomplished a total synthesis of (+/-)-adalinine through a homoallyl nitroalkane derived from Seebach's reagent.
Palladium-Catalyzed alpha-Arylation of Cyclic Vinylogous Esters for the Synthesis of gamma-Arylcyclohexenones and Total Synthesis of Aromatic Podocarpane Diterpenoids
(2017-03-03)
Hou, Wen-Yi
;
Wu, Yen-Ku
;
應用化學系
;
Department of Applied Chemistry
Described is a method for the formal gamma-arylation of cyclohexenones allowing synthesis of a remote all-carbon quaternary center. The process involves the palladium-catalyzed alpha-arylation of a alpha-substituted cyclic vinylogous ester followed by the Stork-Danheiser transposition. The synthetic utility of this protocol is featured in the total syntheses of (+/-)-12-hydroxy-13-methylpodocarpa-8,11,13-trien-3-one, (+/-)-3 beta,12-dihydroxy-13-methylpodocarpane-8,11,13-triene, and (+/-)-O-methyl nimbinone.
Palladium-catalyzed alpha-arylation of indolin-3-ones
(2020-04-30)
Chang, Yu-Hsuan
;
Peng, Wan-Ling
;
Chen, I-Chia
;
Hsu, Hsin-Yun
;
Wu, Yen-Ku
A method for the catalytic alpha-arylation of indolin-3-ones was developed. The catalytic system comprising Pd(dba)(2) and PAd(3) was found to be optimal for the transformation. The protocol features broad functional group compatibility in that a range of arylated indoxyl derivatives bearing a fully substituted carbon center was synthesized with high efficiency. A preliminary bioassay study revealed that the selected indole-substituted indolin-3-ones exhibit favorable cytotoxic activities against HCT-116 cancer cell line.
Palladium-Catalyzed Cascade Arylation of Vinylogous Esters Enabled by Tris(1-adamantyl)phosphine
(2019-12-06)
Yang, Yi-Chi
;
Lin, Yi-Ching
;
Wu, Yen-Ku
;
應用化學系
;
Department of Applied Chemistry
Described is a method for the transformation of a cyclic vinylogous ester to the corresponding polyarylated product. We found a catalytic system comprising palladium diacetate and tris(1-adamantyl)phosphine is quite effective in promoting a set of controlled cascade arylations. As a result, a range of novel (hetero)aryl-containing scaffolds was synthesized with a high level of efficiency.
Palladium-catalyzed N1-selective allylation of indoles with allylic alcohols promoted by titanium tetraisopropoxide
(2019-01-25)
Chang, Chieh-Yu
;
Lin, Yu-Huan
;
Wu, Yen-Ku
;
應用化學系
;
Department of Applied Chemistry
The direct N1-selective allylation of indoles with allylic alcohols has been accomplished by synergistic functions of palladium catalysts and titanium tetraisopropoxide. The site selectivity is notably different from that observed in other related transition metal-catalyzed approaches. This chemistry provides a facile route to a variety of allylated indoles in synthetically useful yields. The utility of this simple allylation reaction was demonstrated with the first total synthesis of (+)-N-(4-hydroxyprenyl)-cyclo(alanyltryptophyl), which was completed in five steps, starting from l-tryptophan methyl ester hydrochloride.
Palladium/Light Induced Radical Alkenylation and Allylation of Alkyl Iodides Using Alkenyl and Allylic Sulfones
(2018-02-16)
Sumino, Shuhei
;
Uno, Misae
;
Huang, Hsin-Ju
;
Wu, Yen-Ku
;
Ryu, Ilhyong
Alkenylation and allylation of alkyl iodides with alkenyl and allyl sulfones, respectively, took place under Pd/photoirradiation system. The initial alkyl radical, derived from a single electron transfer between Pd(0) and RI, underwent the title transformations. Pd(0) was regenerated through a reductive elimination of PhSO2PdI, which is formed by the combination of the sulfonyl radical and the palladium radical. The addition of water was effective, presumably by pushing the equilibrium through hydrolysis of PhSO2I.
Pd/light-induced alkyl-alkenyl coupling reaction between unactivated alkyl iodides and alkenylboronic acids
(2020-05-21)
Huang, Hsin-Ju
;
Wang, Yi-Ting
;
Wu, Yen-Ku
;
Ryu, Ilhyong
;
應用化學系
Alkyl-alkenyl coupling reaction between unactivated alkyl iodides and 2-arylalkenylboronic acids utilizing a Pd/light combined system was studied. This reaction provided 2-alkylarylalkenes in good yields. It is proposed that in this reaction alkyl radicals are formed by SET from a Pd catalyst to alkyl iodides, which then undergo addition reactions to form C-C double bonds of alkenyl boronic acids and the subsequent beta-fragmentation of boronyl radicals leads to the formation of alkyl-substituted arylalkenes.
Rapid construction of tetrahydropyridine scaffolds via formal imino Diels-Alder reactions of Schiff bases and Nazarov reagents
(2019-10-21)
Wu, Yen-Ku
;
Rawal, Viresh H.
;
應用化學系
;
Department of Applied Chemistry
Described is a one-flask, two-step method for the synthesis of highly functionalized piperidines. The process involves formal [4 + 2] cycloadditions of Schiff bases and Nazarov reagents, followed by facile elaborations of the initial cycloadducts. Notably, these aza-annulations are facilitated by protic solvents and proceed smoothly under ambient conditions, without other additives. The synthetic utility of this annulation protocol is further showcased through a concise, convergent synthesis of (+/-)-tetrabenazine.
Revisiting Hydroxyalkylation of Phenols with Cyclic Carbonates
(1970-01-01)
Kao, Shih-Chieh
;
Lin, Yi-Ching
;
Ryu, Ilhyong
;
Wu, Yen-Ku
;
應用化學系
Described is a tetrabutylammonium fluoride-mediated hydroxyalkylation reaction of phenols with cyclic carbonates. This operationally simple method enables the synthesis of a variety of aryl beta-hydroxyethyl ethers in good to excellent yields with a very small amount of catalyst loading (0.1-1 mol%). Of particular note is the efficient conversion of aromatic diols and phloroglucinol to the corresponding bis- and tris-hydroxyethylated products. To further showcase the versatility of this protocol, guaifenesin was prepared with a single step by the condensation of guaiacol and glycerol carbonate. We also developed a flow ethoxylation process permitting the continuous synthesis of multiflorol.
Temperature-Controlled Thiation of alpha-Cyano-beta-Alkynyl Carbonyl Derivatives for De Novo Synthesis of 2-Aminothiophenes and Thieno[2,3-c]isothiazoles
(2018-12-07)
Kao, Tzu-Ting
;
Peng, Bo-Kai
;
Liang, Min-Chieh
;
Lee, Chia-Jui
;
Chen, I-Chia
Making use of temperature-controlled thiation as a key operation, a simple route to 2-aminothiophenes or thieno[2,3-c]isothiazoles has been newly developed wherein the 2-aminothiophene nucleus was formed through an initial formation of thioamide followed by a 5-exo-dig addition to the tethered alkyne; however, under harsher thermal conditions, excess sulfur-transferring reagents enabled further oxidative thiation to generate the corresponding thieno[2,3-c]isothiazoles.