Surface structure determination of silica single layer on Mo(112) by LEED

The atomic structure of silica single layer on a Mo(112) substrate was determined by means of low-energy electron diffraction analysis. The best-fit structure was consistent with findings of previous studies [Phys. Rev. Lett. 95 (2005) 076103 and Phys. Rev. Lett. 103 (2009) 017601]. The unit cell is c(2 × 2)-Si₂O₅ and is composed of a two-dimensional network of SiO₄ tetrahedrons. The tetrahedrons incline slightly to fit the silica network on the Mo(112) surface while maintaining the ideal Si–O bond length. Since there are no dangling bonds in the silica network, the surface is very stable even in the atmosphere.     

Platinum‐Catalyzed Friedel–Crafts‐Type C−H Coupling–Allylic Amination Cascade to Synthesize 3,4‐Fused Tricyclic Indoles

A novel platinum‐catalyzed cascade cyclization reaction was developed by intramolecular Friedel–Crafts‐type C?H coupling of aniline derivatives with a propargyl carbonate unit‐allylic amination sequence. Treatment of various propargyl carbonates tethered to meta‐aniline derivatives with a Pt(dba)₃/DPEphos catalyst system afforded the corresponding 3,4‐fused tricyclic 3‐alkylidene indolines in 42–99 % yield, which were transformed into 3,4‐fused indole derivatives by reaction with trifluoroacetic acid. The reaction products exhibited antiproliferative activities against cancer cells, but not normal cells, revealing the potential usefulness of this reaction for medicinal chemistry.     

Synthesis of novel bidentate P-chiral diaminophosphine oxide preligands: application to Pd-catalyzed asymmetric allylic substitution reactions

We developed a novel (S)-L-phenylalanine derived-bidentate chiral diaminophosphine oxide (DIAPHOX) preligand (S,S(P))-9b, which was successfully applied to Pd-catalyzed asymmetric allylic alkylation and amination. Using the Pd-(S,S(P))-9b catalyst system, asymmetric allylic alkylation and amination proceeded very smoothly, affording the corresponding products in excellent yield with high enantiomeric excess. It is noteworthy that both enantiomers were accessible with high enantiomeric purity using the structurally related DIAPHOX preligands (S,S(P))-9b and a monodentate chiral diaminophosphine oxide preligand (S,R(P))-10a, both of which can be prepared from a single chiral source, (S)-L-phenylalanine.     

Attosecond electron delocalization in the conduction band through the phosphate backbone of genomic DNA

Partial density of states in the empty conduction band of the phosphate backbone sites in DNA was probed using energy-dependent resonant Auger spectroscopy. Results show that genomic DNA with periodic backbones exhibits an extended state despite separation of each phosphate group by an insulating sugar group. In antisense DNA with an aperiodic backbone, the equivalent state is localized. Remarkably rapid electron delocalization occurs at ca. 740 attoseconds for wet DNA, as estimated using the core-hole clock method. Such delocalization is comparable to the Fermi velocity of carbon nanotubes.     

Pd-catalyzed enantioselective synthesis of quaternary α-amino acid derivatives using a phenylalanine-derived P-chirogenic diaminophosphine oxide

A Pd-catalyzed enantioselective synthesis of quaternary α-amino acid derivatives using a phenylalanine-derived P-chirogenic diaminophosphine oxide is described. Asymmetric allylic substitution using acyclic β-keto esters with a nitrogen functional group at the α-carbon as prochiral nucleophiles proceeded in the presence of 5 mol % of Pd catalyst, 10 mol % of chiral diaminophosphine oxide 1j, BSA, and appropriate additives, affording the corresponding quaternary α-amino acid derivatives in excellent yield and in up to 92% ee.     

Strategy for enantio- and diastereoselective syntheses of all possible stereoisomers of 1,3-polyol arrays based on a highly catalyst-controlled epoxidation of alpha,beta-unsaturated morpholinyl amides: application to natural product synthesis

We describe a new strategy for enantio- and diastereoselective syntheses of all possible stereoisomers of 1,3-polyol arrays. This strategy relies on a highly catalyst-controlled epoxidation of alpha,beta-unsaturated morpholinyl amides promoted by the Sm-BINOL-Ph(3)As[double bond]O (1:1:1) complex, followed by a conversion of morpholinyl amides into ketones and diastereoselective ketone reduction. Highly enantio- (up to >99 % ee) or diastereoselective (up to >99.5:0.5) epoxidation was achieved using 5-10 mol % of the Sm complex to afford synthetically very useful, nearly optically pure alpha,beta-epoxy morpholinyl amides. Stereoselectivity of the epoxidation was controlled by the chirality of BINOL with overwhelming inherent diastereofacial preference for the substrate. Combination with the syn- and anti-selective ketone reduction with the highly catalyst-controlled epoxidation allowed for an iterative strategy for the syntheses of all possible stereoisomers of 1,3-polyol arrays. Eight possible stereoisomers of 1,3,5,7-tetraol arrays were synthesized with high to excellent stereoselectivity. Moreover, the efficiency of the present strategy was successfully demonstrated by enantioselective syntheses of several 1,3-polyol/alpha-pyrone natural products, for example, cryptocaryolone diacetate.     

Construction of the multidecker anthracene-silver(I) system by intramolecular pi-pi interactions

As a continuation of the study on the construction of the multidecker aromatic compounds with pi-pi interactions, the anthracene derivatives 9,10-dimethylanthracene (dman), 9,10-diphenylanthracene (dpan), and 7,12-dimethylbenz[a]anthracene (dmban) have been studied toward complexation with the silver(I) ion. The crystal structures of [Ag(dman)(0.5)(p-xylene)(ClO(4))], [Ag(2)(dpan)(0.5)(C(6)H(6))(0.5)(CF(3)SO(3))(2)], and [Ag(2)(dmban)(2)(ClO(4))(2)](p-xylene), together with the metal-free ligand dpan, have been determined by single-crystal X-ray diffraction. These pi-electron-rich aromatic compounds are found to have great promise as an approach to the effective self-assembly of high nuclearity in a multilayer fashion.     

A polar oxide ZnSnO3 with a LiNbO3-type structure

A polar oxide ZnSnO3 was synthesized by a solid-state reaction under a pressure of 7 GPa and a temperature of 1000 degrees C. The crystal structure was determined by Rietveld analysis of the X-ray powder diffraction data. ZnSnO3 has a rhombohedral LiNbO3-type structure with unit cell parameters, a = 0.52622(1) nm, c = 1.40026(2) nm (space group: R3c). The polar structure is characterized by the large displacement of Zn along the c-axis in the ZnO6 octahedron based on the strong chemical bonding between Zn and three O. ZnSnO3 is a candidate piezoelectric and pyroelectric material as well as nonlinear optical material.     

A Direct S0→Tn Transition in the Photoreaction of Heavy-Atom-Containing Molecules

According to the Grotthuss–Draper law, light must be absorbed by a substrate to initiate a photoreaction. There have been several reports, however, on the promotion of photoreactions using hypervalent iodine during irradiation with light from a non-absorbing region. This contradiction gave rise to a mystery regarding photoreactions involving hypervalent iodine. We demonstrated that the photoactivation of hypervalent iodine with light from the apparently non-absorbing region proceeds via a direct S₀→T_n transition, which has been considered a forbidden process. Spectroscopic, computational, and synthetic experimental results support this conclusion. Moreover, the photoactivation mode could be extended to monovalent iodine and bromine, as well as bismuth(III)-containing molecules, providing new possibilities for studying photoreactions that involve heavy-atom-containing molecules.