Original Papers by Youhei Takeda
Crystals and thin films of 1,4-bis(alkenyl)-2,5-dipiperidinobenzenes, which contain only one benz... more Crystals and thin films of 1,4-bis(alkenyl)-2,5-dipiperidinobenzenes, which contain only one benzene ring as the aromatic component, emit visible light with excellent solid-state quantum yields upon irradiation with UV light. Polystyrene thin films doped with the benzenes also exhibit brilliant fluorescence. By modifying the alkenyl groups, the emission color can be tuned in the range from blue to red.
Bookmarks Related papers MentionsView impact
A mild nucleophilic ring-opening reaction of activated aziridines with N-chloro-N-sodio-tert-buty... more A mild nucleophilic ring-opening reaction of activated aziridines with N-chloro-N-sodio-tert-butylcarbamate, which gives differentially protected vicinal diamine derivatives, has been developed. The two protecting groups are selectively removable, and the total synthesis of a long-chain fatty acids oxidation inhibitor, emeriamine, was achieved by using the present method. Boc=tert-butyloxycarbonyl; Ns=nitrophenylsulfonyl.
Bookmarks Related papers MentionsView impact
An intermolecular benzylic C–H bond amination utilizing the combination of chloramine-T and I2 wi... more An intermolecular benzylic C–H bond amination utilizing the combination of chloramine-T and I2 without the aid of transition-metal catalysts has been developed. The reaction was found applicable to a variety of benzene-substituted alkanes, as well as to an adamantane derivative to give N-alkylated p-tosylamides in good yields.
Bookmarks Related papers MentionsView impact
A bi-capped inclusion complex of C60 with organosilylated γ-cyclodextrin that is highly soluble i... more A bi-capped inclusion complex of C60 with organosilylated γ-cyclodextrin that is highly soluble in nonpolar and weakly polar organic solvents, such as CHCl3 or cyclohexane, was prepared and characterized. The complex facilitates the separation of C60 from C70 and selective functionalization of C60. Furthermore, fabrication of a thin film of the complex by using a solution technique was demonstrated.
Bookmarks Related papers MentionsView impact
A direct synthetic method for producing oxazoline-fused fullerenes, that is, fullerooxazoles, fro... more A direct synthetic method for producing oxazoline-fused fullerenes, that is, fullerooxazoles, from [60] fullerene and readily available carboxamides by radical pathways has been developed. The method presented allows efficient access to a variety of fullerooxazoles with high functional compatibility under mild reaction conditions. Furthermore, systematic investigation of their properties, such as solubility, thermostability, and electrochemical behavior, was conducted.
Bookmarks Related papers MentionsView impact
A straightforward, convenient, and efficient synthetic method of azobenzenes through oxidative di... more A straightforward, convenient, and efficient synthetic method of azobenzenes through oxidative dimerization of aromatic amines using a unique and cost-effective iodinating reagent is described. This new method allows for easy access to both of symmetrical and unsymmetrical azobenzenes under extremely mild conditions.
Bookmarks Related papers MentionsView impact
An oxidative skeletal rearrangement of 1,1′-binaphthalene-2,2′-diamines (BINAMs) that involves th... more An oxidative skeletal rearrangement of 1,1′-binaphthalene-2,2′-diamines (BINAMs) that involves the cleavage of a strong C–C single bond of the binaphthalene unit and the nitrogen migration has been discovered. The unprecedented rearrangement enables access to a series of U-shaped azaacenes otherwise difficult to prepare in a selective manner by classical methods. Moreover, physicochemical properties of the unique azaacenes have been comprehensively investigated.
Bookmarks Related papers MentionsView impact
Phosphorus analogues of pyrromellitic diimides (PyDIs), which represent a family of privileged el... more Phosphorus analogues of pyrromellitic diimides (PyDIs), which represent a family of privileged electron-accepting organic compounds, have been successfully synthesized as novel electron-accepting π-conjugated molecules. Investigation into their physicochemical properties uncovered their prominent electron-accepting abilities over the corresponding PyDI. Furthermore, theoretical studies revealed the significant contribution of σ*–π* hyperconjugation in stabilizing the LUMO+1.
Bookmarks Related papers MentionsView impact
Journal of the American Chemical Society, May 29, 2014
A palladium-catalyzed stereospecific and regioselective cross-coupling of enantiopure 2-arylaziri... more A palladium-catalyzed stereospecific and regioselective cross-coupling of enantiopure 2-arylaziridines with arylboronic acids under mild conditions to construct a tertiary stereogenic center has been developed. N-heterocyclic carbene (NHC) ligands efficiently promote the coupling, suppressing β-hydride elimination. The enantiospecific cross-coupling allowed us for preparation of a series of biologically important 2-arylphenethylamine derivatives in an enantiopure form.
Bookmarks Related papers MentionsView impact
Chemistry (Weinheim an der Bergstrasse, Germany), Aug 16, 2013
A PCy3-catalyzed ring-expansion reaction of aziridine-fused fullerenes (aziridinofullerenes) thro... more A PCy3-catalyzed ring-expansion reaction of aziridine-fused fullerenes (aziridinofullerenes) through the insertion of CO2 and aryl isocyanates is disclosed. The reaction allows for CO2 fixation by aziridinofullerenes, producing oxazolidinone-fused fullerenes (oxazolidinofullerenes) in high yields, whereas treatment with aryl isocyanates led to a new fullerene family—imidazolidinone-fused fullerenes (imidazolidinofullerenes)—in good to high yields. Furthermore, a mechanistically related unprecedented fullerenyl phosphonium salt was successfully isolated. Using the isolated salt, mechanistic studies were also investigated.
Bookmarks Related papers MentionsView impact
A straightforward synthetic method of both symmetric and unsymmetric aromatic azo compounds throu... more A straightforward synthetic method of both symmetric and unsymmetric aromatic azo compounds through an efficient and cross-selective oxidative dimerization of aromatic amines using tert-butyl hypoiodite (t-BuOI) under metal-free and mild conditions has been developed. This method was also found applicable to the synthesis of heteroaromatic azo compounds. The spectroscopic study indicates the involvement of N,N-diiodoanilines in the oxidative reaction as the key intermediate.
Bookmarks Related papers MentionsView impact
Chemical communications (Cambridge, England), Aug 14, 2013
Hypervalent iodine(III)-induced oxidative [4+2] annulation of o-phenylenediamines and electron-de... more Hypervalent iodine(III)-induced oxidative [4+2] annulation of o-phenylenediamines and electron-deficient alkynes under metal-free conditions has been developed. The reaction allows for direct access to quinoxalines bearing two electron-withdrawing groups in an efficient manner.
Bookmarks Related papers MentionsView impact
Chemistry (Weinheim an der Bergstrasse, Germany), Aug 14, 2012
Highly selective and versatile methods for the synthesis of aza[60]fulleroids and aziridino[60]fu... more Highly selective and versatile methods for the synthesis of aza[60]fulleroids and aziridino[60]fullerenes from C60 have been developed. The reactions utilized N,N-dihalosulfonamides as an N1 source. The photophysical, electrochemical, and thermal properties of the iminofullerenes were investigated by means of UV/Vis spectroscopy, cyclic voltammetry, and thermogravimetry, respectively. Furthermore, photovoltaic cells based on the synthesized iminofullerenes were fabricated. The power conversion efficiencies (PCEs) of the devices showed moderate values ranging from 1.33 to 2.35 %.
Bookmarks Related papers MentionsView impact
Organic letters, Aug 31, 2012
A cyclizative atmospheric CO2 fixation by unsaturated amines such as allyl and propargyl amines u... more A cyclizative atmospheric CO2 fixation by unsaturated amines such as allyl and propargyl amines under mild reaction conditions, efficiently leading to cyclic carbamates bearing a iodomethyl group, have been developed utilizing tert-butyl hypoiodite (t-BuOI).
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
An oxidative dimerization reaction of aromatic amines utilizing tert-butyl hypoiodite (tBuOI) und... more An oxidative dimerization reaction of aromatic amines utilizing tert-butyl hypoiodite (tBuOI) under mild reaction conditions leads to aromatic azo compounds (see scheme). The method allows access to unsymmetric aromatic azo compounds, which are difficult to prepare by conventional synthetic methods, in a selective manner.
Bookmarks Related papers MentionsView impact
We prepared a Pd complex by the oxidative addition of 1,1-dibromo-3,3,3-trifluoro-2-tosyloxyprope... more We prepared a Pd complex by the oxidative addition of 1,1-dibromo-3,3,3-trifluoro-2-tosyloxypropene to [Pd(PPh3)4]. The atomic distance between Pd and F in the complex was 2.95 Å, which was shorter than the sum of the van der Waals radii. Based on NMR studies of the oxidative addition step, a catalytic cycle for the Pd-catalyzed cross-coupling reaction of the propene is proposed, with the Pd–F interaction as the key element for the Z-selectivity.
Bookmarks Related papers MentionsView impact
Dimethoxybis(3,3,3-trifluo-ropropen-1-yl)benzenes were prepared through palladium-catalyzed doubl... more Dimethoxybis(3,3,3-trifluo-ropropen-1-yl)benzenes were prepared through palladium-catalyzed double cross-coupling reactions of diiododimethoxybenzenes with CF3C≡CZnCl, followed by reduction of CF3C≡C groups with LiAlH4 or H2 in the presence of the Lindlar catalyst. The edges of the absorption spectra of 1,2-(MeO)2-4,5-(CF3CHC=CH)2benzenes 1 and 1,3-(MeO)2-4,6-(CF3CH=CH)2benzenes 2 in cyclohexane ranged from 348 to 360 nm, whereas the absorption spectra of 1,4-(MeO)2-2,5-[(E)-CF3CH=CH]2 benzene ((E)-3) ended at 406 nm. These findings indicate that the effective conjugation length of (E)-3 was significantly larger than those of 1 and 2. Consistently, 1 and 2 in cyclohexane exhibited fluorescence with emission maxima in the UV region, whereas (E)-3 in cyclohexane emitted violet light with an emission maximum at 407 nm. All the fluorescence spectra of 1–3 in various solvents redshifted as the solvent polarity increased. The photoluminescence of 1, E-1, Z-1, 2, E-2, E-2H, Z-2, E-3, E-3H, Z-3 in the solid states was also observed with emission maxima in the violet region. It is important to note that the quantum yields of (E)-3 in a neat thin film and in a doped polymer film were 0.37 and 0.49, respectively. Density functional theory calculations suggested that the fluorine atoms contribute to a slight extension of both the HOMOs and the LUMOs, as well as narrowing of the HOMO–LUMO gaps when compared with the corresponding fluorine-free analogues. In the case of (E)-3, it is suggested that the HOMO–LUMO transition includes charge transfer from the ethereal oxygen atoms to the C(sp2)[BOND]CF3 moieties.
Bookmarks Related papers MentionsView impact
Molecular fluorophores of type A–π–D–π–A (D=donor, A=acceptor) demonstrate solid-state emission i... more Molecular fluorophores of type A–π–D–π–A (D=donor, A=acceptor) demonstrate solid-state emission in the red to near-infrared region with high efficiency. The emission color can be tuned through the substituents on the diarylamino and cyanophenyl moieties. The electroluminescence performance of the designed fluorophore confirms its potential as an emitter for use in organic light-emitting devices.
Bookmarks Related papers MentionsView impact
Heterocycles, Mar 11, 2008
We describe here a facile route to 2-trifluoromethyl-substituted 4,5-dihydrooxepins, which involv... more We describe here a facile route to 2-trifluoromethyl-substituted 4,5-dihydrooxepins, which involves stereoselective preparation and Cope rearrangement of 2-trifluoromethyl-cis-2,3-bis(alkenyl)oxiranes. Treatment of 1,1-dichloro-2-hydroxy-2-trifluoromethylalk-3-enes with alkenyllithium and then lithium 2,2,6,6-tetramethylpiperidide generated cis-2,3-bis(alkenyl)-2-lithio-3- trifluoromethyloxiranes, which reacted with a variety of electrophiles to give the corresponding tri- and tetrasubstituted oxiranes stereoselectively. Cope rearrangement of the cis-oxiranes proceeded upon heating, giving rise to 2-trifluoromethyl-substituted 4,5-dihydrooxepins in high to excellent yields. The Cope rearrangement is found remarkably accelerated by the presence of such metal substituents as boryl, silyl, and stannyl groups at 7-position, that can act as versatile functionalities for further elaboration of the ring-enlarged products. Subsequent reduction and oxidation of the rearranged products gave 2-trifluoromethylated oxepanes and oxepins in good yields.
Bookmarks Related papers MentionsView impact
Uploads
Original Papers by Youhei Takeda