Toru Amaya

Anisotropic Electron Transport Properties in Sumanene Crystal

The high electron mobility with large anisotropy was attained in the needle-like single crystal of sumanene, which was indicated by time-resolved microwave conductivity (TRMC) measurement.

Synthesis of Highly Strained π-Bowls from Sumanene

The short step synthesis of highly strained naphtosumanenes was successfully achieved from sumanene based on a nonpyrolytic approach.

A Dynamically Inverting π‐Bowl Complex

The binding of metals to curved carbon p-surfaces has attracted continuous scientific interest since the discovery of metal complexes of buckminsterfullerene C60. [1–3] Molecules that consist of fragments of C60, that is, buckybowls, open geodesic polyarenes, or p bowls, possess curved carbon psurfaces; examples include corannulene (C20H10) and sumanene (1, C21H12; Figure 1a). [4, 5] From a coordination chemistry

Chemistry of sumanene.

Sumanene (C21 H12 ) is a bowl-shaped π-conjugated molecule with C3v symmetry, consisting of alternating benzene rings and cyclopentadiene rings around the central benzene ring. The structure corresponds to the smallest C3v-symmetric fragment for the structural motifs of fullerenes or end-caps of carbon nanotubes. The presence of three sp(3)-hybridized benzylic sites is one of the most characteristic structural features in sumanene, which allows the different chemistry from that of corannulene. Since our first synthesis in 2003, we have engaged in the study of sumanene. This article summarizes our continuous study, including the synthesis, structure, dynamics, derivatization, complexation with transition metals, charge carrier mobility, and conversion to nitrogen-doped graphitic carbon, of sumanene.

Synthesis and characterization of π-extended bowl-shaped π-conjugated molecules

A series of pi-extended bowl-shaped pi-conjugated compounds were synthesized from sumanene and characterized, and among them the terthiophene derivative showed a remarkable red-shifted absorption and small band gap, which wa rationalized by molecular orbital calculation.

Synthesis of oxosumanenes through benzylic oxidation.

Oxosumanenes were synthesized through benzylic oxidation. The electronic and redox properties were revealed to exhibit the expanded π-conjugation compared to sumanene. Single-crystal X-ray analysis of monooxosumanene showed columnar π-stacking in a concave-convex fashion. Stereoselective trimethylation of the trioxo derivative was performed via 1,2-addition to the carbonyl groups.

A theoretical study of the bowl-to-bowl inversion of sumanene derivatives

A theoretical study was conducted on the bowl-to-bowl inversion of sumanene: its benzylic mono-, di-, and trianion species and its mono-, di-, and trinaphthosumanenes. The use of B3LYP/6-311+G(2d,p) for the B3LYP/6-31G(d,p)-optimized geometries approximately reproduced the experimental values for the bowl-to-bowl inversion of sumanene, and its benzylic mono- and dianion species. The value for the trianion was estimated to be around 21 kcal/mol using the above levels. The investigation of naphthosumanenes clearly indicated a noted increase in the inversion barrier with additional fused rings. The calculated inversion barrier for mononaphthosumanene also correctly reproduced the experimental value (32.2 kcal/mol) using the above levels (31.4 kcal/mol). The calculated barrier for trinaphthosumanene reached 63.8 kcal/mol, therefore, the bowl-to-bowl inversion is less likely to occur under realistic conditions.

Parallel synthesis of multi-branched oligosaccharides related to elicitor active pentasaccharide in rice cell based on orthogonal deprotection and glycosylation strategy

Abstract We describe a parallel and efficient synthesis of multi-branched oligosaccharides 3a–g based upon the structure of the phytoalexin elicitor active branched pentasaccharide 2 . One-pot sequential orthogonal deprotection of tetrasaccharide 5 with three different protecting groups provided each of seven glycosyl acceptors 4a–g . Glycosylation of the acceptors 4a–g , followed by deprotection provided branched oligosaccharides 3a–g . All the reaction processes from scaffold 5 to 3a–g except for final hydrogenolysis were achieved utilizing an automated synthesizer in a parallel fashion.

Bowl Inversion of Surface-Adsorbed Sumanene

Bowl-shaped π-conjugated compounds offer the possibility to study curvature-dependent host-guest interactions and chemical reactivity in ideal model systems. For surface-adsorbed π bowls, however, only conformations with the bowl opening pointing away from the surface have been observed so far. Here we show for sumanene on Ag(111) that both bowl-up and bowl-down conformations can be stabilized. Analysis of the molecular layer as a function of coverage reveals an unprecedented structural phase transition involving a bowl inversion of one-third of the molecules. On the basis of scanning tunneling microscopy (STM) and complementary atomistic simulations, we develop a model that describes the observed phase transition in terms of a subtle interplay between inversion-dependent adsorption energies and intermolecular interactions. In addition, we explore the coexisting bowl-up and -down conformations with respect to host-guest binding of methane. STM reveals a clear energetic preference for methane binding to the concave face of sumanene.

Selective Intermolecular Oxidative Cross-Coupling of Enolates.

Selective intermolecular oxidative cross-coupling of enolates, which is a bond-forming reaction between carbanion equivalents, remains as an unsolved issue despite its potential utility for the direct synthesis of unsymmetrical 1,4-diones. The main difficulty derives from the unavoidable homo-coupling. Our strategy depends on the selective one-electron oxidation of one enolate to afford an electrophilic carbonyl α-radical species, followed by trapping with another enolate. The present study demonstrates the selective oxovanadium(V)-induced cross-coupling between boron and silyl enolates.