Tatsuo Okauchi

Vinylic CF bond activation with low-valent zirconocene: the generation and cross-coupling reactions of 1-fluorovinylzirconocene

Abstract (p-2,2-Difluorovinyloxyphenyl)dimethylamine, readily obtained from 2,2,2-trifluoroethanol, is treated with zirconocene equivalent ‘Cp2Zr’ to generate thermostable 1-fluorovinylzirconocene via a CF bond cleavage. This 1-fluorovinylzirconocene can be used for CC bond formation through the cross-coupling with aryl iodides in the presence of palladium catalyst and zinc iodide, leading to (Z)-1-aryl-2-(p-dimethylaminophenoxy)-1-fluoroolefins in good yields.

Novel 2,2-difluorovinylzirconocene: A facile synthesis of monosubstituted gem-difluoroolefinsvia its cross-coupling reaction

Abstract 2,2-Difluorovinyl p-toluenesulfonate, readily obtained from 2,2,2-trifluoroethanol, is treated with zirconocene equivalent “Cp 2 Zr” to generate the remarkably themostable nonsubstituted 2,2-difluorovinylzirconocene, which in turn couples with aryliodides in the presence of palladium catalyst and zinc iodide to afford monosubstituted gem-difluoroolefins in high yields. The reaction proceeds via 2,2-difluorovinylzinc as confirmed by 19 F-NMR measurement.

α-Phosphonovinyl nonaflate: Their synthesis and cross-coupling reactions

Abstract A new class of vinylphosphonates, α-phosphonovinyl nonafluorobutanesulfonates ( i.e. nonaflates) is readily prepared from the corresponding acylphosphonates and nonafluorobutanesulfonyl fluoride in the presence of DBU. The obtained nonaflates are converted to the phosphono-containing enynes and dienes via Pd catalyzed coupling reactions.

Development of chiral phosphine ligands bearing a carboxyl group and their application to catalytic asymmetric reaction

Abstract A new chiral phosphine ligand bearing a carboxyl group, 3-(diphenylphosphino)butanoic acid, was developed and used for palladium catalyzed asymmetric allylic alkylation of cyclic cis-allylic acetates such as 2-cyclopentenyl, 2-cyclohexenyl, and 2-cycloheptenyl acetate. These acetates reacted with triethyl sodiophosphonoacetate in the presence of the palladium catalyst with the ligand to give the corresponding alkylation products in good enantiomeric excesses.

Long-term air-stable n-channel organic thin-film transistors using 2,5-difluoro-1,4-phenylene-bis{2-[4-(trifluoromethyl)phenyl]acrylonitrile}.

A long-term air-stable n-type organic semiconductor, 2,5-difluoro-1,4-phenylene-bis{2-[4-(trifluoromethyl)phenyl]acrylonitrile}, was synthesized by a high-yield simple procedure of Knoevenagel condensation with aldehyde and acetonitrile derivatives. A fabricated organic thin-film transistor (OTFT) using this compound exhibited good n-channel OTFT properties with a high electron mobility of 0.17 cm(2) V(-1) s(-1) and an on/off current ratio of 10(6) under both vacuum and ambient air operation. After storage in ambient air for 1 year, a stored n-channel OTFT still shows good n-channel OTFT performance with little degradation in ambient air operation.

Asymmetric allylic alkylation of cycloalkenediol diacetates using a chiral phosphine ligand bearing a carboxyl group

Abstract Asymmetric induction in the allylic alkylation of cycloalkenediol diacetates was performed using a chiral alkylphosphine ligand bearing a carboxyl group, 3-(diphenylphosphino)butanoic acid. An increase in enantiomeric excess of the monoalkylated products of cis-cycloalkenediol diacetates was observed through a sequential asymmetric allylic alkylation–kinetic resolution process.

Pd(OAc)2-Catalyzed Macrocyclization of 1,2-Diazonaphthoquinones with Cyclic Ethers

Pd(OAc)2 was found to be an efficient catalyst for the macrocyclization of 1,2-diazonaphthoquinones and cyclic ethers. This transformation serves as an efficient method for the synthesis of protected 1,2-naphthalenediols.

A Selective G-Quadruplex DNA-Stabilizing Ligand Based on a Cyclic Naphthalene Diimide Derivative

A cyclic naphthalene diimide (cyclic NDI, 1), carrying a benzene moiety as linker chain, was synthesized and its interaction with G-quadruplex DNAs of a-core and a-coreTT as a human telomeric DNA, c-kit and c-myc as DNA sequence at promoter region, or thrombin-binding aptamer (TBA) studied based on UV-VIS and circular dichroism (CD) spectroscopic techniques, thermal melting temperature measurement, and FRET-melting assay. The circular dichroism spectra showed that 1 induced the formation of different types of G-quadruplex DNA structure. Compound 1 bound to these G-quadruplexes with affinities in the range of 106–107 M−1 order and a 2:1 stoichiometry. Compound 1 showed 270-fold higher selectivity for a-core than dsDNA with a preferable a-core binding than a-coreTT, c-kit, c-myc and TBA in the presence of K+, which is supported by thermal melting studies. The FRET-melting assay also showed that 1 bound preferentially to human telomeric DNA. Compound 1 showed potent inhibition against telomerase activity with an IC50 value of 0.9 μM and preferable binding to G-quadruplexes DNA than our previously published cyclic NDI derivative 3 carrying a benzene moiety as longer linker chain.

A Steady Operation of n-Type Organic Thin-Film Transistors with Cyano-Substituted Distyrylbenzene Derivative

A novel n-type organic semiconductor, cyano-substituted distyrylbenzene derivative, 1,4-bis2-[4-(trifluoromethyl)phenyl]acrylonitorilebenzene, was synthesized by Knoevenagel condensation with aldehyde and acetonitrile derivatives. Fabricated thin-film transistors (TFTs) exhibited high electron field-effect mobility of 10-2–10-1 cm2 V-1 s-1, on/off current ratio of 6×105. Hysteresis-free n-type transport characteristics observed in this device promises a steady operation of organic logic circuit. Almost same TFT characteristic was observed even after 1 month storage in ambient condition. The findings indicate that the material has a good resistance to atmospheric oxidants.

Studies of inositol 1-phosphate analogues as inhibitors of the phosphatidylinositol phosphate synthase in mycobacteria

We previously reported a novel pathway for the biosynthesis of phosphatidylinositol in mycobacteria via phosphatidylinositol phosphate (PIP) [Morii H., Ogawa, M., Fukuda, K., Taniguchi, H., and Koga, Y (2010) J. Biochem. 148, 593-602]. PIP synthase in the pathway is a promising target for the development of new anti-mycobacterium drugs. In the present study, we evaluated the characteristics of the PIP synthase of Mycobacterium tuberculosis. Four types of compounds were chemically synthesized based on the assumption that structural homologues of inositol 1-phosphate, a PIP synthase substrate, would act as PIP synthase inhibitors, and the results confirmed that all synthesized compounds inhibited PIP synthase activity. The phosphonate analogue of inositol 1-phosphate (Ino-C-P) had the greatest inhibitory effect among the synthesized compounds examined. Kinetic analysis indicated that Ino-C-P acted as a competitive inhibitor of inositol 1-phosphate. The IC(50) value for Ino-C-P inhibition of the PIP synthase activity was estimated to be 2.0 mM. Interestingly, Ino-C-P was utilized in the same manner as the normal PIP synthase substrate, leading to the synthesis of a phosphonate analogue of PIP (PI-C-P), which had a structure similar to that of the natural product, PIP. In addition, PI-C-P had high inhibitory activity against PIP synthase.