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Title compounds (III) are prepared by benzannulation reaction of 9,10-bis(arylethynyl)anthracene derivatives (I) and 2-(phenylethynyl)benzaldehyde (II) in the presence of Cu or Re catalyst, resp., and trichloroacetic acid.

“Kekulene” is a doughnut-like shaped polycyclic aromatic hydrocarbon consisting of cyclically arrayed benzene rings. It has attracted a great deal of theoretical interest because it is regarded as an ideal model to study conjugation circuits of π electrons, i.e. whether they delocalize locally in benzene rings or globally throughout the molecule. Though kekulene was synthesized in 1978, it was the only known compound of this class of compounds for a long time. Recently, new kekulene-related molecules, septulene, which is a non-alternant benzenoid hydrocarbon, and a tetracyclopentatetraphenylene (TCPTP) derivative belonging to non-alternant non-benzenoid hydrocarbons, were synthesized. This article presents theoretical and experimental aspects of kekulene-related molecules focusing on the viewpoint of conjugation circuits by classifying them into three types: benzenoid kekulenes including kekulene itself and septulene, yet unknown anti-kekulene and non-alternant non-benzenoid kekulenes represented by TCPTP.

Compound (I), a derivative of the hitherto unknown title compound which is a potential tetraradicaloid hydrocarbon, is synthesized in five steps starting from a known polycyclic tetracarboxylic acid (synthetic pathway not shown).

The development of the chemistry of non-alternant non-benzenoid hydrocarbons is reviewed in connection with the International Symposium on Novel Aromatic Compounds (ISNA) and the author's personal anecdotes. Past molecules include the classics of this class of compounds, pentalene, azulene, and heptalene, and the structurally integrated congeners such as indacenes formed by benzannelation and benzinterposition, which were extensively studied during the last century. Indenofluorene isomers constructed by benzannelation to indacenes represent present molecules, which have attracted much interest in recent years in view of their potential in optoelectronic applications. The unusual properties of the most exotic isomer, indeno[2,1-b]fluorene, are specifically described to demonstrate that the benzannelation is not simply a modification for stabilization. Finally, as future molecules, those consisting of linear and cyclic arrays of indenofluorene motifs formed by further extension are proposed.

Review: synthesis, molecular structures, and physical properties relevant to biradical character of indenofluorene isomers; 60 refs.

The title compounds (III) are obtained by Cu- or Re-catalyzed double benzannulation of 2-(phenylethynyl)benzaldehyde with various butadiynes.

3,5-Dinitro-1,4-dihydropyridines (DNDHPs) are readily constructed by the acid-promoted self-condensation of β-formyl-β-nitroenamines. In the DNDHPs, one molecule of the nitroenamine serves as a C3N1 building block and the other serves as a C2 block. This synthetic method does not require any special reagents and conditions. When the reaction is conducted in the presence of electron-rich benzene derivatives, arylation at the 4-position of DNDHP is achieved by trapping the 3,5-dinitropyridinium ion intermediate.

Pt-catalyzed cyclization of o-dialkynylbenzene derivatives bearing a hydroxyethyl group [cf.

At the liquid/graphite interface triangular and rhombic phenylene–ethynylene macrocycles substituted by alkyl chains self-assemble to form porous two-dimensional (2D) molecular networks of honeycomb and Kagome types, respectively, or close-packed non-porous structures via alkyl chain interdigitation as the directional intermolecular linkages. Factors that affect the formation of the 2D molecular networks, such as alkyl chain length, solvent, solute concentration, and co-adsorption of guest molecules, were elucidated through a systematic study. For the porous networks, various molecules and molecular clusters were adsorbed in the pores reflecting the size and shape complementarity, exploring a new field of 2D host–guest chemistry.

The synthesis and structural characterization of a hitherto unknown tetradehydro - dinaphtho(10)annulene, which had eluded isolation since attempts initiated during the late 1960s, was achieved. Moreover, the dehydroannulene was transformed into stable derivatives of zethrene, which was first reported in 1955, but forgotten for a long time. These molecules are substituted at the 7,14-positions and open the door to the zethrene family for potential ap- plication as optoelectronic materials.

The first total syntheses and structural studies of [6] (1,4) naphthalenophane (4) and [6] (1,4) anthracenophane (5), the smallest-bridged isolable cyclophanes with bent acene nuclei, are disclosed. The acenophanes 4 and 5 were successfully synthesized by the oxidative decarboxylation of benzo- and naphtho-fused propellenecarboxylic acids: the bridgehead olefins followed by subsequent treatment with potassium tert-butoxide

An acid-catalyzed rearrangement of tricyclo[5.4.0.01,5]undecan-ll-one gave tricyclo[5.3.1.01,5]undecan-11-one in a nonnucleophilic media and tricyclo[5.4.0.03,8]undecane-7, 8-diol in the presence of a nucleophile, respectively. Tricyclo[5.4.0.01,5]undecan-11-ols also rearranged to tricyclo[5.4.0.03,8]undecan-7-ol. A reductive rearrangement with a hydride transfer of the alcohol gave only tricyclo[5.4.0.03,8]undecane.

Irradiation of 3-methoxyphenol in the presence of 2 equiv of AlBr3 in CH2Cl2 gave 4-methoxybicyclo[3.1.0]hex-3-en-2-one in a 38% yield. 3-Methoxy-2-methylphenol also yielded the lumiketone rearrangement product. On the other hand, 3-methoxy-4-methyl-, 3-methoxy-5-methyl-, and 5-methoxy-2-methylphenol underwent transposition of the methyl group to give equilibrium mixtures of the three methoxycresols.

[6](1,4)Naphthalenophane ( 1 ) and [6](1,4)anthracenophane ( 2 ) underwent thermal cycloaddition with tetracyanoethylene to give the corresponding [2+2] adducts 3 and 4 . Anthracenophane 2 reacted with dimethyl acetylenedicarboxylate to yield the 1:1 and 1:2 adducts 6 and 7 .

8-Methoxycarbonyl substituted [6](1,4)naphthaleno- and [6](1,4)anthracenophanes were prepared by the thermal valence isomerization of the corresponding hemi-Dewar type valence isomers. The rates of their isomerization were remarkably faster than those of the Dewar isomer of [6]paracyclophanes.

A new class of cyclam, octamethylcyclam, and its related compounds bearing tetramethylethane, cis-cyclohexane, or trans-cyclohexane subunit(s) have been synthesized. Nickel(II) complexes with sterically congested ligands have been shown to be low-spin complexes in water, while those with less congested ligands to be mixtures of low-spin and high-spin ones. Nickel(II) complexes with sterically congested ligands have been also exhibited to have higher half-wave potentials (E1/2(NiII,III)) than those of the complexes with less congested ligands.

The unusual reactivity of [6](1,4)naphthalenophane (2) and [6](1,4)anthracenophane (3), the smallest-bridged acenophanes hitherto known, in electrophilic reactions has been disclosed. These reactions include (i) acid-catalyzed telomerization, (ii) peracid oxidation, and (iii) addition with dienophiles. Semi-empirical molecular orbital calculations (MNDO and MNDO/PM3) were performed in order to compare the geometries, energies, and bonding characters of 2 and 3 with those of [6]paracyclophane (1)

Novel photoreactions of 1- and 2-naphthols with ethylene promoted by aluminum halides are described. Irradiation of 2-naphthol (2a) with AlX 3 (X=Cl, Br) and ethylene in CH 2 Cl 2 gave the corresponding [2+2] cycloadduct 7a in good yields. The major side product was 2-ethyl-1-naphthol (8a). Of the Lewis acids and alkenes examined, only AlCl 3 and AlBr 3 effected the reaction and only ethylene gave satisfactory results, although allene can also be employed. Naphthols 2b-e having different electron-attracting substituents on C-6 afforded [2+2] adducts 7b-e in moderate to good yields, while the reactions of C-3-alkyl-substituted derivatives 8a and 15b were unsuccessful

Metalation of [6]paracyclophane ( 1 ) with a superbase generated metalocyclophanes 2a and 3a regioselectively which led to mono substituted derivatives 2b – 2e and para disubstituted 3b , 3d , and 3e .

Pig liver esterase, lipase from porcine pancreas, lipase from Pseudomonas sp. (lipase YS), and lipase from Candida cylindracea catalyzed hydrolyses of the cis-diacetate 1 and the trans-diacetate (±)-4 to give the cis-monoacetate 3 and the trans-monoacetate 6 in optically active forms, respectively. Lipase YS-catalyzed acylations of the cis-diol 2 and the trans-diol (±)-5 with an acylating agent in cyclohexane yielded (−)-3 and (−)-6, respectively. The group adjacent to the R stereogenic center preferentially reacted in lipase YS-catalyzed hydrolyses of 1 and (±)-4 and acylations of 2 and (±)-5, and the enantioselectivities are rationalized by our rule recently proposed for lipase YS.

Photolysis of trienediynes (1a) and (1b) and trienetetrayne (1c) having a [4.3.2]propellane framework yielded the respective lines polyynes (2a-c) in good efficiency through [2+2] cycloreversion, extruding indan (3)

Homochiral 1-(1-adamantyl)ethane-1,2-diol ( 5 ) was prepared and its absolute configuration was determined to be ( S )-(+)- 5 by enzymatic and 1 H n.m.r. spectroscopic methods. Using ( S )-(+)- 5 as a chiral subunit, the homochiral crown ether (+)- 18 was synthesized and its enantioselectivity in complexation of methionine methyl ester perchlorate was also examined by the 1 H n.m.r. spectroscopic method.

Extremely air- and acid-sensitive [6](9,10)anthracenophane (1), the smallest-9,10-bridged anthracene, has been synthesized by reductive deoxygenation of diepoxyanthracenophane (4) with a low-valent titanium reagent, and it was characterized by its NMR and electronic spectrum

Cis- and trans-2-phenylcyclohexano-14-crown-4 and cis- and trans-2,3-diphenylcyclohexano-14-crown-4 were prepared and their ion selectivity was determined by means of extraction of alkali metal picrates, stability constants, and ion-selective electrodes. Cis diphenyl derivative exhibits the highest lithium ion-selectivity of the four ionophores examined, which is as high as that of decalino-14-crown-4, one of the best Li+-selective ionophores.

Homochiral azophenolic crown ethers 1 and 2 having three chiral barriers, that is, the phenyl group, the methyl group, and the cyclohexane moiety on each of the homotopic faces have been prepared. The enantiomer recognition toward chiral 2-aminoethanol derivatives has been examined.

Primary alcohols having a hydroxymethyl group at an S stereogemic center and secondary alcohols with an R configuration are preferentially acylated to give the corresponding acetates by lipase YS (from Pseudomonas fluorescens )-catalyzed acylation using isopropenyl acetate as the acylating agent in diisopropyl ether. On the basis of enantiomer selectivities observed, a predictive active site model for lipase YS is proposed for identifying which enantiomer of a primary or a secondary alcohol reacts faster in this acylation.

The design and synthesis of chiral crown ethers possessing a chiral recognition ability which carry great potential for separation of enantiomers and analytical purpose has become an important and rapidly growing field of host-guest chemistry. One of the advantages of crown ethers constructed using a synthetic chiral building block is that it is rather easy to modify the chiral cavity resulting in the improvement in enantiomer selectivity. Cyclohexane-1,2-diol derivatives such as cis -1-phenylcyclohexane-1,2-diol, trans -1-phenylcyclohexane-1,2-diol and trans - 1,2-diphenylcyclohexane-1,2-diol are of interest as chiral building blocks of crown ethers, because incorporation of these subunits into the 18-crown-6 framework causes a reduction in conformational flexibility of the chiral cavity and fixes the phenyl chiral barrier perpendicularly above the face of crown ring to modify enantiomer recognition ability. Chiral crown ethers of the 18-crown-6 type were synthesized using these building blocks and their chiral recognition behaviour in differential enantiomer transport through bulk liquid membranes were examined. Chiral azophenolic crown ethers containing cis -1-phenylcyclohexane-1,2-diol or cis -cyclohexane-1,2-diol which can bind neutral amines to form a stable complex and exhibit enantiorecognitive coloration in complexation with chiral amines were prepared and the association constants for their complexes with chiral ethylamine and ethanolamine derivatives were determined on the basis of UV-visible absorbance. The observed enantioselectivity is rationalized in terms of complementarity between a host and a guest as indicated by CPK molecular model examination. The alternation of the position of chiral barriers resulted in a reversal of the enantioselectivity. Crown ethers with diastereotopic faces can bind a guest to each side of the diastereotopic faces to form diastereoisomeric complexes which occasionally cause troublesome “sidedness” problems. In order to avoid the problems, most crown ethers previously prepared contained at least one C 2 axis of symmetry. However, diastereotopic face selectivity in complexation does provide helpful information on the complexing behaviour of crown ethers to assist in the design of more elaborate and structured host molecules. meso -Crown ethers having cis-1-phenylcyclohexane-1,2-diol were prepared and the diastereotopic face selectivity by their diastereotopic faces in complexation with achiral amines was examined by temperature-dependent 1H nuclear magnetic resonance. Ethanolamine is attached stereoselectively to one of the faces to give one of diastereoisomeric complexes and the alternation of the position of steric barriers led to reversal of the diastereotopic face selectivity. A prediction of which diastereoisomeric complex is formed is made on the basis of CPK molecular model.

[6](9,10)Anthracenophane (1a) was synthesized by the benzoannelation method starting from dibromo[6]paracyclophane 6 via diepoxyanthracenophanes 3a and 4a. In a similar fashion, peri-substituted de...

Lipase QL-catalyzed acylation of secondary alcohols using isopropenyl acetate as the acylating agent in diisopropyl ether gave preferentially the corresponding acetate with an R configuration. On the basis of the results, a predictive active site model for lipase QL is proposed for identifying which enantiomer of a secondary alcohol reacts faster in this reaction.

Lipase QL (from Alcaligenes sp.)-catalyzed acylation of alcohols using isopropenyl acetate as the acylating agent in diisopropyl ether converted preferentially primary alcohols with an S configuration and secondary alcohols with an R configuration into the corresponding homochiral acetates. On the basis of observed enantiomer selectivities, a predictive active site model for lipase QL is proposed for identifying which enantiomer of a primary or a secondary alcohol reacts faster in this acylation.