Rui Umeda

Tetradehydrodinaphtho[10]annulene: A Hitherto Unknown Dehydroannulene and a Viable Precursor to Stable Zethrene Derivatives

The synthesis and structural characterization of hitherto unknown tetradehydrodinaphtho[10]annulene, a hydrocarbon whose synthesis had been attempted four decades ago, was achieved for the first time. Moreover, the dinaphtho[10]annulene was transformed smoothly into stable zethrene derivatives substituted at its 7,14-positions, showing that it serves as a good reservoir of zethrene derivatives. Optical and electrochemical properties of a disubstituted zethrene derivative are also presented.

Tetradehydrodinaphtho[10]annulene and its transformation into zethrene: A hitherto unknown dehydroannulene and a forgotten aromatic hydrocarbon

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 application as optoelectronic materials.

Ag-catalyzed stereoselective cyclohexadienyl transfer: a novel entry into arylphenylmethanols.

The letter describes a novel concept for the synthesis of biologically important arylphenylmethanols. Stereoselective cyclohexadienyl transfer from 1,4-cyclohexadienyltributyltin to various aromatic aldehydes using AgOTf/BINAP as a catalyst precursor provides 1,4-cyclohexadienylphen-ylmethanols that are readily oxidized to the corresponding arylphenylmethanols. Fifteen examples are presented.

Rhenium‐Catalyzed Benzannulation of o‐Alkynylbenzaldehyde with Alkynes to Multiple 2,3‐Disubstituted Naphthalenes

The development of a synthetic method of multiple substituted polycyclic aromatic hydrocarbons has attracted a great deal of interest because of their potential applications as functional materials in various electronic devices, such as organic semiconductors, organic light-emitting diodes, solar cells, and molecule-based sensory devices. Thus, the development of a convenient and selective synthetic method to produce polysubstituted aromatic compounds has been a challenging problem in organic synthesis. To this end, the benzannulation reaction is one of the promising approaches for their selective synthesis. Recently, Yamamoto and Asao et al. have reported that Au and Cu-catalyzed [4+2] benzannulation between o-alkynylbenzaldehydes and alkynes is an effective strategy for the synthesis of various naphthalenes. Based on this finding, various types of aromatic compounds were prepared by the transition metal-catalyzed [4+2] benzannulation between the enynal, including o-alkynylbenzaldehydes and various unsaturated compounds. It was proposed that the coordination of a transition metal to the carbon–carbon triple bond is a key step in these benzannulation reactions. Alternatively, the utility of rhenium complexes as a catalyst has recently been shown in various organic synthesis and it is suggested that rhenium complexes have not only coordinating to a heteroatom on the heteroatom–carbon bond (s-electrophilic Lewis acid), but also coordinating to carbon–carbon multiple bonds (p-electrophilic Lewis acid) from these reactions. We have now found that the rhenium-catalyzed benzannulation of o-alkynylbenzaldehydes and alkynes proceeded in the co-presence of Brønsted acid to give the corresponding 2,3disubstituted naphthalenes (Scheme 1). This is the first example of the rhenium complex catalyzed benzannulation reaction. Furthermore, we applied the current transformation to the synthesis of multiple and sterically hindered polycyclic aromatic hydrocarbons having 2,3-disubstituted naphthalene units. First, the treatment of o-(2-phenylethynyl)benzaldehyde (1 a, 0.30 mmol) and 1-phenyl-1-propyne (2 a, 0.36 mmol) in the presence of a catalytic amount of ReBr(CO)5 gave 2-methyl-3phenylnaphthalene (3 a) as the sole product in only 11 % yield (entry 1). Yamamoto and Asao have disclosed that Cu(OTf)2-catalyzed benzannulation between o-alkynylbenzaldehyde and alkyne was promoted by the addition of Brønsted acid. Therefore, we investigated the effect of a additive of various Brønsted acids to the rhenium-catalyzed system and these results are shown in Table 1. With the additive of p-touenesulfonic acid and benzoic acid as a Brønsted acid, the yield of 3 a slightly increased (Table 1, entries 2 and 3). When several types of acetic acids were added to the reactions, the yield of 3 a was improved (entries 4-8) and trichloroacetic acid gave the best result (51 %, entry 7). The yield of 3 a was dramatically increased using small excess amounts of 1 a and trichloroacetic acid (entries 9 and 10) and 3 a was obtained in 78 % yield.

Vinylidene to alkyne rearrangement to form polyynes: synthesis and photolysis of dialkynylmethylenebicyclo[4.3.1]deca-1,3,5-triene derivatives

Abstract Dialkynylmethylenebicyclo[4.3.1]deca-1,3,5-triene derivatives were synthesized as precursors to generate dialkynylvinylidenes by extrusion of an aromatic fragment, indane. Photolysis of the trienes gave linear polyynes as the major products produced by rearrangement of the vinylidenes, together with the isomerization products having a methylenecycloheptatriene moiety.

Molecular Propellers that Consist of Dehydrobenzo[14]annulene Blades

A new class of propel- ler-shaped compound (4), which consisted of dehydrobenzo[14]annulene ([14]DBA) blades, as well as its naphtho homologues (5 and 6), have been prepared. Although NMR studies of compound 4 did not provide useful information regarding its conformation in solution, DFT calculations with different functionals and the 6-31G* basis set all indicated that the D(3)-symmetric structure was energetically more favorable than the C(2) conformer. From X-ray crystallographic analysis, it appeared that compound 4 adopted a propeller-shaped-, approximately D(3)-symmetric structure in the solid state, in which the [14]DBA blades were twisted substantially owing to steric repulsion between the neighboring benzene rings. On the contrary, in the case of compound 6, although the DFT calculations with the B3LYP functional predicted that the D(3)-symmetric conformation was more stable, calculations with the M05 and M05-2X functionals indicated that the C(2) conformer was more favorable because of π-π interactions between the naphthalene units of a pair of neighboring blades. Indeed, X-ray analysis of compound 6 showed that it adopted an approximately C(2)-symmetric conformation. Moreover, on the basis of variable-temperature (1)H NMR measurements, we found that compound 6 adopted a C(2) conformation and the barrier for interconversion between the C(2)-C(2) conformers was estimated to be 16.2 kcal mol(-1); however, no indication of the presence of the D(3) isomer was obtained. The relatively small energy barriers to interconversion, despite the large overlapping of neighboring blades, was ascribed to the flexibility of the acetylene linkages, which could be deformed substantially in the transition state of the ring-flip.

Cesium Carbonate-Catalyzed α-Phenylchalcogenation of Carbonyl Compounds with Diphenyl Dichalcogenide

It was found that cesium carbonate has a unique catalytic ability on the reaction of carbonyl compounds with diphenyl diselenide to give the corresponding α-phenylseleno carbonyl compounds in moderate to good yields. Similarly, the α-phenylthiolation of carbonyl compounds with diphenyl disulfide was promoted by the cesium carbonate catalyst.

PtCl2-Catalyzed Cyclization of o-Diethynylbenzene Derivatives Triggered by Intramolecular Nucleophilic Attack

Abstract PtCl2-catalyzed cyclization of o-diethynylbenzene derivatives bearing a hydroxyethyl group yielded naphthofuran derivatives by initial intramolecular cyclization of the hydroxy group to an activated ethynyl group followed by attack of the second ethynyl group to a vinylplatinum intermediate. When the ethynyl terminal is substituted by a hydroxypropyl group, not only homologous naphthodihydropyran but also indenylidenetetrahydrofuran derivatives were formed.

Selective Metallation of 3-Halothiophenes: Practical Methods for the Synthesis of 2-Bromo-3-formylthiophene

Abstract Selective lithiation of 3-bromothiophene was accomplished under controlled conditions without formation of undesired thienyllithium compounds. A thienyl Grignard reagent derived from 2-bromo-3-iodothiophene was transformed into 2-bromo-3-formylthiophene in high selectivity by formylation with dimethylformamide (DMF) at optimal reaction temperature.

Synthesis of 4H-benz[de]anthracen-4-ones via 1,2-addition of metal acetylides to benzanthrone

ABSTRACT Easy and facile syntheses of the 4H-benz[de]anthracen-4-one derivatives were achieved by the reaction of benzanthrone and lithium acetylides, followed by the treatment with silica gel in CHCl3. GRAPHICAL ABSTRACT