Waro Nakanishi

Bio: Waro Nakanishi is an academic researcher from Wakayama University. The author has contributed to research in topics: Hypervalent molecule & Chemical shift. The author has an hindex of 26, co-authored 130 publications receiving 2171 citations. Previous affiliations of Waro Nakanishi include Kitasato University & Florida State University College of Arts and Sciences.

Atoms-in-Molecules Dual Parameter Analysis of Weak to Strong Interactions: Behaviors of Electronic Energy Densities versus Laplacian of Electron Densities at Bond Critical Points

Abstract: AIM dual parameter analysis is proposed for the better understanding of weak to strong interactions: Total electron energy densities (Hb(rc)) are plotted versus Laplacian of electron densities (Δρb(rc)) at bond critical points (BCPs). Interactions examined in this work are those in van der Waals adducts, hydrogen bonded complexes, molecular complexes and hypervalent adducts through charge transfer (CT) interactions, and some classical covalent bonds. Data calculated at BCPs for the optimized distances (ro), together with ro − 0.1 A, ro + 0.1 A, and ro + 0.2 A, are employed for the plots. The plots of Hb(rc) versus Δρb(rc) start from near origin (Hb(rc) = Δρb(rc) = 0) and turn to the right drawing a helical stream as a whole. The helical nature is demonstrated to be controlled by the relative magnitudes of kinetic energy densities (Gb(rc)) and potential energy densities (Vb(rc)), where Gb(rc) + Vb(rc) = Hb(rc). Requirements for the data to appear in the specified quadrant are clarified. Points correspondin...

Highly Regioselective Amination of Unactivated Alkanes by Hypervalent Sulfonylimino-λ3-Bromane

Abstract: Amination of alkanes has generally required metal catalysts and/or high temperatures. Here we report that simple exposure of a broad range of alkanes to N-triflylimino-λ3-bromane 1 at ambient temperature results in C–H insertion of the nitrogen functionality to afford triflyl-substituted amines in moderate to high yields. Marked selectivity for tertiary over secondary C–H bonds was observed; primary (methyl) C–H bonds were inert. Addition of hexafluoroisopropanol to inhibit decomposition of 1 dramatically improved the C–H amination efficiencies. Second-order kinetics, activation parameters (negative activation entropy), deuterium isotope effects, and theoretical calculations suggest a concerted asynchronous bimolecular transition state for the metal-free C–H amination event.

Attractive Interaction Caused by the Linear F···Se−C Alignment in Naphthalene Peri Positions

Abstract: The X-ray crystallographic analysis of 8-fluoro-1-(p-anisylselanyl)naphthalene (1) revealed that the F and Se atoms and the ipso-carbon of the p-anisyl group (C(An)) aligned linearly The F atom and the Se−C(An) bond lay on the naphthyl plane: the nonbonded distance between F and Se atoms was 2753(3) A and the FSeC(An) angle was 1750(1)° Ab initio MO calculations with the 6-311++G(3df,2pd) basis sets performed on the model compound of 1, HF···SeH2, where the aryl groups of 1 were replaced by hydrogens The calculations exhibited that the energy minimum was achieved when the F, Se, and C(An) atoms aligned linearly Charge transfer in the formation of HF···SeH2 was suggested to occur from F to SeH2 on the basis of natural population analysis, which supported the npx(F)−σ*(Se−C(An)) interaction

Polar coordinate representation of Hb(rc) versus (h2/8m)nabla2rhob(rc) at BCP in AIM analysis: classification and evaluation of weak to strong interactions.

Abstract: Polar coordinate (R, θ) representation is proposed for the plot of Hb(rc) versus (ℏ2/8m)▽2ρb(rc) in AIM analysis to classify, evaluate, and understand weak to strong interactions in a unified way and in more detail; Hb(rc) and ▽2ρb(rc) are total electron energy densities and the Laplacian of ρb(rc) at bond critical points (BCPs: rc), respectively, where ρb(rc) are electron densities at rc. Both the x- and y-axes of the plot are expressed in the common unit of energy since Hb(rc) = Gb(rc) + Vb(rc) and (ℏ2/8m)▽2ρb(rc) = Hb(rc) − Vb(rc)/2 (= Gb(rc) + Vb(rc)/2), where Gb(rc) and Vb(rc) are kinetic energy densities and potential energy densities, respectively. Data employed for the plot are calculated at BCPs for full-optimized structures and optimized structures with the fixed distances (r) of r = ro + wao, where ro are the full-optimized distances, ao is the Bohr radius, and w = ±0.1 and ±0.2. The plot draws a helical stream starting from near origin (Hb(rc) = (ℏ2/8m)▽2ρb(rc) = 0) for very weak interactions ...

Novel Substituent Effect on 77Se NMR Chemical Shifts Caused by 4c-6e versus 2c-4e and 3c-4e in Naphthalene Peri Positions: Spectroscopic and Theoretical Study

Abstract: δ(8Se) values for 1-[8-(p-YC6H4Se)C10H6]SeSe[C10H6(SeC6H4Y-p)-8‘]-1‘ (1: Y = H, OMe, Me, Cl, Br, COOEt, and NO2) showed a good correlation with those of 1-(MeSe)-8-(p-YC6H4Se)C10H6 (2). While the δ(1Se) values correlated well with δ(8Se) in 2 with a positive proportionality constant of 0.252 (regular correlation), a similar correlation for 1 gave a negative proportionality constant of −0.282 (inverse correlation). To clarify the mechanism associated with the inverse correlation in 1, together with the regular correlation in 2, ab initio MO calculations, containing the GIAO magnetic shielding tensor for the Se nucleus (σ(Se)), were performed on p-YC6H4ASeH- - -BSeH−BSeH- - -HASeC6H4Y-p (3: model of Se4 4c-6e for 1) and on p-YC6H4ASeH- - -BSeH2 (4 and 5: models of Se2 π type 2c-4e and ASe- - -BSe−H 3c-4e for 2, respectively) with the 6-311+G(2d,p) basis sets at B3LYP and/or HF levels. The characteristic nature of the substituent effects on atomic charges and δ(Se) values in 3 is demonstrated to be Yδ-←C6H...

The Halogen Bond

Abstract: The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.

Advances in Synthetic Applications of Hypervalent Iodine Compounds

Abstract: The preparation, structure, and chemistry of hypervalent iodine compounds are reviewed with emphasis on their synthetic application. Compounds of iodine possess reactivity similar to that of transition metals, but have the advantage of environmental sustainability and efficient utilization of natural resources. These compounds are widely used in organic synthesis as selective oxidants and environmentally friendly reagents. Synthetic uses of hypervalent iodine reagents in halogenation reactions, various oxidations, rearrangements, aminations, C–C bond-forming reactions, and transition metal-catalyzed reactions are summarized and discussed. Recent discovery of hypervalent catalytic systems and recyclable reagents, and the development of new enantioselective reactions using chiral hypervalent iodine compounds represent a particularly important achievement in the field of hypervalent iodine chemistry. One of the goals of this Review is to attract the attention of the scientific community as to the benefits of...

Organoselenium chemistry: role of intramolecular interactions.

Abstract: In 1836 the first organoselenium compound, diethyl selenide, was prepared by Löwig,1 and it was isolated in the pure form in 1869.2 Early selenium chemistry involved the synthesis of simple aliphatic compounds such as selenols (RSeH), selenides (RSeR), and diselenides (RSeSeR); however, because of their malodorous nature, these compounds were difficult to handle. This, combined with the instability of certain derivatives and difficulties in purification, meant that selenium chemistry was slow to develop. By the 1950s, the number of known selenium compounds had increased significantly, but it was not until the 1970s, when several new reactions leading to novel compounds with unusual properties were discovered, that selenium chemistry began to attract more general interest.3-9 Aryl-substituted compounds were synthesized that were found to be less volatile and more pleasant to handle than the earlier aliphatic compounds. Compounds containing selenium in high oxidation states are relatively easy to manipulate using modern techniques.4c Organoselenium chemistry has now become a well-established field of research, and recent advances have been brought about by the potential technical applications of selenium compounds. Today selenium compounds find application in many areas including organic synthesis,4 biochemistry,5 xerography,6 the synthesis of conducting materials7 and semiconductors,8 and ligand chemistry.4c,9 Many of these aspects of selenium chemistry are wellcovered elsewhere in the literature; however, the subject of hypervalency has not attracted much attention and is the focus of this review.10

Metal-catalysed azidation of tertiary C–H bonds suitable for late-stage functionalization

Abstract: Many enzymes oxidize unactivated aliphatic C-H bonds selectively to form alcohols; however, biological systems do not possess enzymes that catalyse the analogous aminations of C-H bonds. The absence of such enzymes limits the discovery of potential medicinal candidates because nitrogen-containing groups are crucial to the biological activity of therapeutic agents and clinically useful natural products. In one prominent example illustrating the importance of incorporating nitrogen-based functionality, the conversion of the ketone of erythromycin to the -N(Me)CH2- group in azithromycin leads to a compound that can be dosed once daily with a shorter treatment time. For such reasons, synthetic chemists have sought catalysts that directly convert C-H bonds to C-N bonds. Most currently used catalysts for C-H bond amination are ill suited to the intermolecular functionalization of complex molecules because they require excess substrate or directing groups, harsh reaction conditions, weak or acidic C-H bonds, or reagents containing specialized groups on the nitrogen atom. Among C-H bond amination reactions, those forming a C-N bond at a tertiary alkyl group would be particularly valuable, because this linkage is difficult to form from ketones or alcohols that might be created in a biosynthetic pathway by oxidation. Here we report a mild, selective, iron-catalysed azidation of tertiary C-H bonds that occurs without excess of the valuable substrate. The reaction tolerates aqueous environments and is suitable for the functionalization of complex structures in the late stages of a multistep synthesis. Moreover, this azidation makes it possible to install a range of nitrogen-based functional groups, including those from Huisgen 'click' cycloadditions and the Staudinger ligation. We anticipate that these reactions will create opportunities to modify natural products, their precursors and their derivatives to produce analogues that contain different polarity and charge as a result of nitrogen-containing groups. It could also be used to help identify targets of biologically active molecules by creating a point of attachment--for example, to fluorescent tags or 'handles' for affinity chromatography--directly on complex molecular structures.