Atsunori Mori

Direct amination of azoles via catalytic C-H, N-H coupling.

C-H, N-H Coupling of azoles takes place with several amines in the presence of a copper catalyst to undergo amination at the 2-position. The reaction of benzothiazole with N-methylaniline in the presence of sodium acetate and 20 mol % Cu(OAc)(2) in xylene under an oxygen atmosphere afforded the aminated product in 81% yield.

Interfacial Electron-Transfer Kinetics in Metal-Free Organic Dye-Sensitized Solar Cells: Combined Effects of Molecular Structure of Dyes and Electrolytes

Electron diffusion coefficient, lifetime, and density in the TiO(2) electrode of dye-sensitized TiO(2) solar cells (DSCs) employing I(-)/I(3)(-) redox couples were measured with eight different metal-free organic dyes and three Ru complex dyes. At matched electron density, all DSCs using organic dyes (ODSCs) showed shorter electron lifetime with comparable or larger diffusion coefficients in comparison to the DSCs using the Ru dyes (RuDSC). The shorter lifetime was attributed partially to the slower dye cation reduction rate of the organic dyes by I(-), faster electron diffusion coefficient in the TiO(2), and mostly higher I(3)(-) concentration in the vicinity of the TiO(2) surface. Whereas a slight shift of the conduction band edge potential (E(cb)) of the TiO(2) was seen with a few organic dyes, no correlation was found with the dipole moment of the adsorbed dyes. This implies that the adsorbed dyes interact with cations in the electrolyte, so the direction of the dipole is altered or simply screened. The increase of [I(3)(-)] in the vicinity of the TiO(2) surface was interpreted with partial charge distribution of the dyes. Under one-sun conditions, less electron density due to shorter electron lifetime was found to be the main reason for the lower values of V(oc) for all ODSCs in comparison to that of RuDSCs. Among the organic dyes, having larger molecular size and alkyl chains showed longer electron lifetime, and thus higher V(oc). Toward higher open circuit voltage, a design guide of organic dyes controlling the electron lifetime is discussed.

C–H Functionalization Polycondensation of Chlorothiophenes in the Presence of Nickel Catalyst with Stoichiometric or Catalytically Generated Magnesium Amide

Polymerization of 2-chloro-3-substituted thiophenes proceeded with a stoichiometric amount of magnesium amide, TMPMgCl·LiCl, or a combination of a Grignard reagent and a catalytic amount of secondary amine in the presence of a nickel catalyst. Although the nickel-catalyzed polymerization with NiCl(2)dppe, which exhibited high catalytic activity in the reaction of bromothiophenes, was less effective, use of a nickel catalyst bearing N-heterocyclic carbene as a ligand was found to induce polymerization with controlled molecular weight and molecular weight distribution.

Palladium-catalyzed C-H functionalization of heteroarenes with aryl bromides and chlorides.

Palladium-catalyzed C-H arylation of electron-enriched heteroarenes with aryl bromides and aryl chlorides proceeds in the presence of LiO-t-Bu as a base. The reaction allows one-pot synthesis of differently substituted 2,5-diarylthiazole with the same catalyst system by switching the solvent and the amount of base.

Substituted carbazole dyes for efficient molecular photovoltaics: long electron lifetime and high open circuit voltage performance

We designed and synthesized new substituted carbazole dyes, MK-14 and -16, for dye-sensitized solar cells (DSSCs) employing the I−/I3−redox couple. By the addition of a hexyloxyphenyl substituent to previously reported carbazole dyes MK-1 and -2, the electron lifetime and open circuit voltage of the DSSCs employing these dyes were increased, showing comparable values with those using a conventional Ru complex dye. This result was achieved by the retardation of the charge recombination, caused by more effective blocking of the I3− ion in the electrolyte than that in the cases of MK-1 and -2. The result shows the importance of the position of alkyl chains attached to the main framework of dye molecules.

Asymmetric simmons-smith reactions using homochiral protecting groups

Abstract Asymmetric Simmons-Smith reactions of α,β-unsaturated acetals derived from chiral dialkyl tartrate or (2 R ,4 R )-2,4-pentanediol are described. Treatment of the acetal with diethylzinc and methylene iodide gives a cyclopropane with high diastereoselectivity. The acetal group is readily transformed to the aldehyde or the ester group. In addition, the method is successfully applied to the enantioselective synthesis of 5,6-methanoleukotriene A4, a stable and selective inhibitor of leukotriene biosynthesis.

A novel C-C bond forming reaction of aryl- and alkenylsilanols. A halogen-free mizoroki-heck type reaction

Abstract When dimethyl(phenyl)silanol is subjected to on electron-deficient olefin in the presence of a stoichiometric amount of Pd(OAc)2, substitution of the CH bond of the olefin by a phenyl group on the silanol occurs in 52–86% yields. The reactions of several aryl- and alkenylsilanols with several olefins are also found to proceed in the system of 10 mol% of Pd(OAc)2, Cu(OAc)2 (3 mol), LiOAc (2 mol) to give the corresponding products in up to 69% yield.

Nucleophilic cleavage of acetals using organometallic reagents

Abstract A highly chemo- and stereo-selective cleavage of acetals derived from (−)(2 R ,4 R )-2,4-pentanediol with organoaluminum and organotitanium reagents has been demonstrated. The reactions proceed under mild conditions with excellent yields and high chemoselectivities to give, after removal of the auxiliary, chiral alcohols of high enantiomeric purities.

Stereoselective reduction of acetals. A method for reductive generation of heterocyclic ring systems

Abstract A new synthetic process for the construction of oxygen-containing heterocyclic systems starting from bicyclic acetals is described. We have investigated the mechanism and the stereochemical course of the reductive cleavage of acetals.

Synthesis of Well-Defined Head-to-Tail-Type Oligothiophenes by Regioselective Deprotonation of 3-Substituted Thiophenes and Nickel-Catalyzed Cross-Coupling Reaction

Iterative growth of thiophene oligomers by single-step extensions has been realized by regioselective metalation of 3-substituted thiophenes with the Knochel-Hauser base (TMPMgCl·LiCl) and coupling with bromothiophene using a nickel catalyst. Treatment of 3-hexylthiophene with TMPMgCl·LiCl induces metalation at the 5-position selectively. Subsequent addition of 2-bromo-3-hexylthiophene and a nickel catalyst leads to the corresponding bithiophene. The obtained bithiophene is converted to the terthiophene and then to the quaterthiophene by repeating the similar protocol. A concise synthesis of MK-1 and MK-2, which are organic dye molecules bearing an oligothiophene moiety that are used in photovoltaic cells, has been achieved.