Naoto Hayashi

Synthesis and properties of unsymmetrically extended π-electronic conjugation system of octaethylporphyrin(Ni)-dihexybithiophene-octaethylporphyrin(Pd) connected with diacetylene linkage

Abstract Orientational isomers of the diacetylene-group connected dihexybithiophene (DHBTh) derivatives have been synthesized, in which the different octaethylporphyrin (OEP(M); M=Ni or Pd) rings are attached at the ends. Reflecting the unsymmetrical structural feature, the peculiar electronic properties of the extended OEP(Ni)–DHBTh–OEP(Pd) system were observed.

X/π Interactions in Aromatic Heterocycles: Basic Principles and Recent Advances

This article outlines the basic principles and recent advances of XH/π interactions involving heteroaromatic molecules or moieties, which include π/π interactions, CH/π interactions, cation/π interactions, anion/π interactions, NH/π and OH/π interactions, and lone-pair/π interactions. Their fundamental features (such as interaction energies and favorable geometries) investigated by means of high-level theoretical calculations and statistical studies are described and compared to interactions involving aromatic hydrocarbons. Several typical or unique examples, where XH/π interactions play a significant role in construction of crystal and supramolecular structures and/or in modulating the properties are shown. The interplay of π/π interaction and hydrogen bonding is also mentioned.

FISCHER INDOLE SYNTHESIS IN THE ABSENCE OF A SOLVENT

The traditional Fischer synthesis of indoles has been investigated and it has been shown that the reaction proceeds in good yield in the absence of a solvent. Introduction In 1883, while studying the reactivity of arylhydrazines and arylhydrazones, Emil Fischer found that, under acidic conditions, enolizable arylhydrazones undergo rearrangement and loss of ammonia to provide indole products (1-3). Subsequent studies suggested a mechanism for the Fischer indole synthesis that proceeds through an initial acid-catalyzed tautomerization of an arylhydrazone to an ene-hydrazine. The ene-hydrazine then undergoes [3,3]-sigmatropic rearrangement to produce a bis-imine intermediate. Subsequent aromatization of the imlnocyclohexadlene ring followed by intramolecular nucleophilic attack produces an aminal, which after loss of ammonia affords the indole product (4). Over 100 years after the initial discovery, the Fischer indole synthesis remains the most commonly employed method for the preparation of Indoles (5,6) Since a novel entry into the Fischer indole synthesis via a palladium-catalyzed strategy for the preparation of hydrazones has recently been developed particularly by Buchwald (7,8), the scope of Fischer Indole synthesis has expanded. Recently combinatorial syntheses of indole derivatives have been reported (9). On the other hand, many advantages of solvent free reactions have been recognized such as reduced pollution, low costs, and simplicity in process and handling (10). We now report that the classical Fischer indole synthesis can be achieved in the absence of a solvent that is followed by a simple work up of the reaction products. Results and Discussion A mixture of Phenylhydrazine l a , 3-pentanone, and p-toluenesulfonic acid (molar ratio 1:1:3) was heated, with mixing, in a test tube, on a water bath, at around 100 °C for 5 mln. The crude product was collected by filtration, washed with water and dried to give 2-ethyl-3-methylindole In Vol. 9. No. 1, 2003 Fischer indole synthesis in the absence of a solvent 82 % yield. Other examples of the reaction products are summarized In Table 1. ρ -TsOH · H 2 0 (3 mmol) R2 JHNH2 (HCl) 1 ( 1 mmol) 2 ( 1 mmol) solvent-free 100 °C (250 °C)

The effect of substitution of the C–F group for the C–H group in crystal packing as well as thermal behaviour

The packing motif and/or thermal stability of a crystal is controlled by intermolecular C–F···π interactions.

Synthesis and electronic properties of hexylthiophene–octaethylporphyrin derivatives (HTh–OEP) connected with diacetylene linkage: substituent effect on the electronic structure of the extended HTh–OEP conjugation system

Abstract Octaethylporphyrin (OEP) was combined with 2-substituted 3-hexylthiophenes (HTh) by diacetylene linkage to afford the highly extended conjugation system (HTh–OEP). Their absorption spectral properties were examined, proving that the electronic structure of OEP is affected by the more electron-withdrawing substituents through the diacetylene linkage more dramatically. The substituent effect on the HTh–OEP conjugation system is much outstanding, as compared with that on the corresponding benzene system (Bzn–OEP).

Generation of 1,1′-Diethynylferrocene for Practical Use: One-Pot Synthesis of 1,1′-Bis(Diacetylene)–Connected Ferrocene Derivative

1,1′-Diethynylferrocene was readily generated for practical use from the trimethylsilyl-protected precursor under modified Eglinton conditions. An oxidative coupling reaction of this reactive species with phenylacetylene successively took place to afford the corresponding 1,1′-bis(diacetylene) connected ferrocene derivative.

Synthesis and electronic properties of dinucleic octaethylporphyrin (OEP) derivatives spaced with p-phenylene group [OEP-(p-Phen)n-OEP].: A comparative study with dihexylbithiophene (DHBTh) group-spaced OEP dimers [OEP-(DHBTh)n-OEP]

Abstract The dinucleic octaethylporphyrin (OEP) derivatives described as OEP-(p-Phen)n-OEP (n = 1–4) were synthesized, in each of which the porphyrin ring is spaced with p-phenylene group. Their electronic properties were studied, as compared with those of the corresponding dihexylbithiophene (DHBTh) derivatives with head-to-head (HH) and tail-to-tail (TT) orientations. It proves that OEP-(p-Phen)n-OEP possesses an in-between feature of OEP-(HH-DHBTh)n-OEP and OEP-(TT-DHBTh)n-OEP in electronic properties.

A FACILE AND SOLVENT-FREE SYNTHESIS OF 3,5 -DISUBSTITUTED-4-AMINO-1,2,4-TRIAZOLES BY REACTIONS OF AROMATIC NITRILES WITH HYDRAZINE

A variety of 3, 5-disubstituted-4-amino-l,2,4-triazoles were prepared by reactions of aromatic nitriles with hydrazine monohydrate. The structure of 3.5-diphenyl-4-amino-l ,2,4-triazoIe was established by an X-ray analysis. 4-Amino-1,2,4-triazoles derivatives have rather Interesting activities such as fungicides (la-c), herbicides and pesticides (2), and more recently, have been used as organic electroluminescent material and devices (Id). 4-Amino-1,2.4-triazoles have been prepared by a number of methods (2). Previously, we reported preparation of a variety of 3,6-diaryl-l, 2, 4, 5-tetrazines and their inverse electron demand Diels-Alder reaction with cyclooctyne (3). During the course of preparation of a variety of 3,6-diaryl-l, 2, 4, 5-tetrazines from aromatic nitriles and hydrazine, we obtained colorless solids when a mixture of these was vigorously refluxed (4). Fortunately, one of the compounds formed a single crystal which was subjected to an X-ray analysis and was unambiguously proven to be 3,5-diphenyl-4-amino-l,2,4-triazole (5). Therefore, we describe below briefly a facile and solvent-free synthesis of 3,5-disubstituted-4-amino-l,2,4-triazoles 3 by reactions of aromatic nitriles 1 with hydrazine monohydrate 2. The reaction procedure is extremely simple: for example, a mixture of benzonirile Jla (4.95g. 0.048 mol) with hydrazine monohydrate 2 (14.447g, 0.288 mol) was refluxed for 48 h. The colorless precipitates were separated by filtration which were dried under vacuum giving crude 3.5-diphenyl-4-amino-l,2,4triazole 3a in 74 % yield (4.2 g) (6). The analytically pure sample was obtained by recrystallizing from ethanol.

Syntheses and reactivities of non-symmetrical “active ester” bi-dentate cross-linking reagents having a phthalimidoyl and acid chloride, 2-benzothiazole, or 1-benzotriazole group

We have newly synthesized the non-symmetrical phthalimidoyl active ester bi-dentate cross-linking reagents having an acid chloride, 2-benzothiazole, or 1-benzotriazole group (i.e., 9, 15, and 16) on the basis of the reactivity study of the active ester model compounds, 11-14, toward the various nucleophiles and examined their reaction selectivity towards the same nucleophiles. Then, we applied for the modification of cholesterol at the more reactive site of the bi-dentate linkers to give 3β-cholesteryl 4-(phthalimidoyloxycarbonyl)butyrate (39), and the subsequent reaction of 39 with several amines, such as benzylamine, 4-chlorobenzylamine, 2-phenylethylamine, L-phenylalanine methyl ester, or diphenylalanine benzyl ester as a protein model of the cholesterol antigen.

Effect of aryl substituents on intramolecular cyclization of 2,2′-biphenoquinones

Effect of aryl substituents on intramolecular cyclizations of 3,3,5,5-tetraaryl-2,2-biphenoquinones (Ar = phenyl (la) and 4-methoxyphenyl (1b)) has been studied. In benzene, la gave 2,4,6,8-tetraphenyldibenzofuran-l-ol (10) gradually as a main product, indicating the phenyl substituents preferred to stabilize the intermediate by delocalization of the negative charge rather than that of the positive one. In contrast, the reaction of lb occurred spontaneously in order to give a complex mixture, which should be due to 4-methoxyphenyl substituent at the 3 position.