Enantioselective Dehydroxyhydrogenation of 3-Indolylmethanols by the Combined Use of Benzothiazoline and Chiral Phosphoric Acid: Construction of a Tertiary Carbon Center.

The chiral indole is an important structure in organic chemistry. We have developed an enantioselective hydrogen transfer reaction of indolylmethanol, which is characterized by the combined use of benzothiazoline and a newly synthesized chiral phosphoric acid. The reaction furnished indoles bearing a chiral tertiary carbon center at the 3-position in high to excellent yields and with excellent enantioselectivities, most of which are greater than 95% ee.

Enantioselective Friedel-Crafts Alkylation Reaction of Heteroarenes with N-Unprotected Trifluoromethyl Ketimines by Means of Chiral Phosphoric Acid.

An enantioselective Friedel-Crafts alkylation reaction of pyrroles and indoles with N-unprotected trifluoromethyl ketimines by use of chiral phosphoric acid provided α-trifluoromethylated primary amines bearing chiral tetrasubstituted carbon centers in high yields and with high to excellent enantioselectivities. The present reaction is unique to N-unprotected trifluoromethyl ketimines. No reaction took place with N-p-methoxyphenyl (PMP)-substituted ketimine.

Material Clocking by Silica Nanoparticle Precipitation in Solution Phase that is Tunable by Organic Molecules.

Material clocking is an important biological phenomenon through which the structure of a material changes sharply with time after activation. A suspension of silica (P)-nanoparticles in the presence of organic molecules in solution exhibits such a material clocking phenomenon during delayed precipitation with high accuracy and precision. A mixture of ethynylhelicene (P)-pentamer and silica (P)-nanoparticles with an average diameter of 70 nm grafted with (P)-helicene in trifluoromethylbenzene is sonicated for activation and dispersion.

Helicene-Grafted Silica Nanoparticles Capture Hetero-Double-Helix Intermediates during Self-Assembly Gelation.

A mixture of a pseudoenantiomeric ethynylhelicene (M)-tetramer and a (P)-pentamer forms a hetero-double-helix in a solution, which self-assembles and gelates solvents. When gelation was conducted in the presence of chiral silica (P)-nanoparticles grafted with (P)-helicene, the resulting hetero-double-helix intermediate was adsorbed on the (P)-nanoparticles, and was removed from the solution by aggregation and precipitation. The resulting precipitates contained only the hetero-double-helix, not random coil or clusters of the hetero-double-helix.

Equilibrium crossing exhibited by an ethynylhelicene (M)-nonamer during random-coil-to-double-helix thermal transition in solution.

The structural change between the random-coil and the double-helix of an ethynylhelicene (M)-nonamer during heating crosses equilibrium. This is a phenomenon where a chemical reaction crosses equilibrium and returns to equilibrium. It is due to an accelerated rate of formation of the double-helix by self-catalysis and an equilibrium shift.

Equilibrium shift in solution: molecular shape recognition and precipitation of a synthetic double helix using helicene-grafted silica nanoparticles.

Chiral silica nanoparticles (70 nm) grafted with (P)-helicene recognized the molecular shape of double helix and random coil (P)-ethynylhelicene oligomers in solution. A mixture of the (P)-nanoparticles and double helix precipitated much faster than a mixture of the (P)-nanoparticles and random coil, and the precipitate contained only the double helix. The mixture of the (P)-nanoparticles and (P)-ethynylhelicene pentamer reversibly dispersed in trifluoromethylbenzene upon heating at 70 °C and precipitated upon cooling at 25 °C.

Optical resolution of aromatic alcohols using silica nanoparticles grafted with helicene.

Optically active silica nanoparticles, with a 70-nm diameter, grafted with (P)-1,12-dimethyl-8-methoxycarbonylbenzo[c]phenanthrene-5-carboxyamide were synthesized, and their use in the kinetic resolution of aromatic alcohols was examined. Up to 61% ee for (S)-2,2-dimethyl-1-phenyl-1-propanol was obtained by a preferential precipitation of aggregates formed with (P)-nanoparticles.