Naoto Hayashi

High pressure mediated three component Strecker synthesis of α-aminonitriles from ketones, aromatic amines and trimethylsilyl cyanide

High pressure (600 MPa) reaction conditions, in the absence of a catalyst, have proved to be a powerful way to stimulate the three component Strecker reaction synthesis of α-aminonitriles in high yields. Examples of two types of double Strecker reactions were also described.

Coumarin–Spiropyran Dyad with a Hydrogenated Pyran Moiety for Rapid, Selective, and Sensitive Fluorometric Detection of Cyanide Anion

We synthesized a coumarin-spiropyran dyad with a hydrogenated pyran moiety (2), behaving as an off-on type fluorescent receptor for rapid, selective, and sensitive detection of cyanide anion (CN(-)) in aqueous media. The receptor itself shows almost no fluorescence with a quantum yield < 0.01, due to the delocalization of π-electrons over the molecule. Selective nucleophilic addition of CN(-) to the spirocarbon of the molecule rapidly promotes spirocycle opening within only 3 min. This leads to localization of π-electrons on the coumarin moiety and exhibits strong light-blue fluorescence at 459 nm with very high quantum yield (0.52). As a result of this, the receptor facilitates rapid, selective, and sensitive fluorometric detection of CN(-) as low as 1.0 μM.

An even–odd effect in inclusion properties and crystal structures of a new host series based on linearly condensed polythiophenes

For a new host series 1a–4c the host–guest (Me2SO) composition and the conformation of the host molecule in the crystalline inclusion compounds are dependent on whether the number of condensed thiophene rings in the host compound is even or odd.

An unusual cobalt-mediated cleavage of a hindered alkyne

Abstract When 1-(pentaphenylphenyl)-2-phenylacetylene (1) is heated with (η5-cyclopentadienyl)dicarbonylcobalt, 1,2,3,4-tetraphenylfluorene (3) and related minor products are formed rather than the expected tetraarylcyclobutadiene. The formation of 3 requires that a seven-carbon fragment (formally a phenylcarbyne) must be lost. Two minor products, however, result from intramolecular cyclization of the alkyne and these two retain all of the carbons from the starting material.

First synthesis of 4, 6-dialkyl-1, 2, 3- triazinones via dialkylcyclopropenones

2-Methyl-4,6-dialkyl-1,2,3-triazin-5(2H)-ones (12a-e) were prepared for the first time from the corresponding cyclopropenones that were prepared by Nakamuras method.

Synthesis of 2,3,4-triphenyl-3-azabicyclo[3.2.0]hepta-1,4-diene and its novel reaction with dimethyl acetylenedicarboxylate

A 3-azabicyclo[3.2.0]hepta-1,4-diene that is unsubstituted in the cyclobutene moiety has been prepared for the first time and undergoes a novel reaction with dimethyl acetylenedicarboxylate to give azepine 6.

QUINONE DIMERS CONNECTED BY 1,4-PHENYLENE AND 2,5-THIENYLENE MOIETIES AS A π-LINKER

The synthesis and characterization of quinone dimers connected by 1,4-phenylene (QPQ) and 2,5-thienylene (QTQ) linkers are described. QPQ and QTQ were synthesized by means of Suzuki coupling and subsequent oxidation. Significant bathochromic shifts were observed in the electronic absorption spectra of QPQ and QTQ as compared to that of the quinine dimers without a linker. In addition, cyclic voltammetry and DFT calculations demonstrated that QTQ was a stronger electron acceptor than QPQ due to its planar structure, even though QTQ contains an electron-rich thiophene ring.

Isomorphic clathrate crystals of isomeric host compounds based on thieno[2,3-b]thiophene and thieno[2,3-b]thiophene

Two isomeric host compounds 1 and 2, which are similar in shape and size to each other, afford crystalline host–guest inclusion complexes in different host:guest ratios with only an exception for Me2SO, a guest compound with strong hydrogen-bonding ability, to form isomorphic crystals of [1][Me2SO]2 and [2][Me2SO]2.

Synthesis of Au Nanoparticles with Benzoic Acid as Reductant and Surface Stabilizer Promoted Solely by UV Light

Photoreductive synthesis of colloidal gold nanoparticles (AuNPs) from Au3+ is one important process for nanoprocessing. Several methods have been proposed; however, there is no report of a method capable of producing AuNPs with inexpensive reagents acting as both reductant and surface stabilizer, promoted solely under photoirradiation. We found that UV irradiation of water with Au3+ and benzoic acid successfully produces monodispersed AuNPs, where thermal reduction does not occur in the dark condition even at elevated temperatures. Photoexcitation of a benzoate-Au3+ complex reduces Au3+ while oxidizing benzoic acid. The benzoic acid molecules are adsorbed on the AuNPs and act as surface stabilizers. Change in light intensity and benzoic acid amount successfully creates AuNPs with controllable sizes. The obtained AuNPs can easily be redispersed in an organic solvent or loaded onto a solid support by simple treatments.

1,3-Dipolar Cycloaddition of Ethyl 2,3-Pentadienoate with Pyridinium Dicyanomethylides: Regiospecific Formation of Ethyl 3-Cyano-2-ethylindolizine-1-carboxylates and a Novel Formation of Tricyclic Compounds

Pyridinium dicyanomethylides underwent site- and regioslective 1,3-dipolar cycloaddition with ethyl 2,3-pentadienoate to give ethyl 3-cyano-2-ethylindolizine-1-carboxylates in moderate yields. In two cases, a novel type of the tricycle compounds, in addition to indolizines, were obtained whose structure was established by a single crystal X-Ray analysis. A plausible mechanism for its formation is also presented.