Search

An algorithm to parallelize the Metropolis sampling was devised and applied to the Monte Carlo simulations using quantum mechanical calculations (QM/MC simulations). As a 4 CPU calculation needs 670 000 s to finish the same QM/MC simulation with the parallelized program, the present algorism reduced the computational time to almost half as long as that of one CPU calculation. The parallelized QM/MC simulation was applied to Diels-Alder reactions between methylvinylketone and cyclopentadiene. The QM/MC (B3LYP/6-311++G∗∗//MP2/6-31G∗,PM3) calculation gave averaged activation energies of 12.7, 13.8 and 15.2 kcal mol−1 in aqueous, methanol and propane solutions. These results are well consistent with those observed.

It is possible to create novel synthetic routes for compounds using synthesis route design systems (SRDS). We have been investigating an in silico screening protocol, which makes it possible to reduce the number of SRDS experiments in developing new synthesis routes. However, there still remains the problem of how to rank synthesis routes for experiments. The experimental yield is considered to be one of the most important factors in determining which synthesis route is better. The present study describes an attempt toward predicting the trends of experimental yields for organic synthesis by fusing computational chemistry and chemoinformatics. We examined whether the prediction of experimental yields for Diels–Alder reactions is feasible using activation energies obtained from Density Functional Theory (DFT) calculations together with the experimental conditions. A partial least squares analysis using these values gave correlation equations for the experimental yields. If it is possible to construct similar correlation equations for other reactions, then SRDS synthetic routes could be ranked on the basis of their predicted yields, and an order can be determined before beginning the experiments.

In this paper we report on the asymmetric 1,3-dipolar cycloaddition reactions of nitrile oxides mediated by pybox/ytterbium triflates, -/magnesium bromide, and -/magnesium perchlorate. It was confirmed that the reactions proceed smoothly to give isoxazoline derivatives in high enantiomeric excesses with Mg2+ or Yb3+ complexes and acrylamide dipolarophiles bearing an oxazolidinone or imidazolidinone coordination auxiliary as well as a pybox ligand. In reactions with a dipolarophile bearing 4,4-dimethyloxazolidinone as the coordination auxiliary, an enantiomeric excess (59 % ee) of the corresponding cycloaddition product was achieved by using a slow addition technique to generate nitrile oxides in the presence of Yb(OTf)3/ph-pybox. The cycloaddition reaction of a dipolarophile with an unsubstituted oxazolidinone group in the presence of Yb(OTf)3/ph-pybox at a relatively high temperature (35 °C) produced a higher enantiomeric excess. A relatively low temperature (–78 °C) was required to obtain enantiomeric excesses such as 69 and 87 % ee in the reactions of a dipolarophile bearing an imidazolidinone group to afford cycloadducts in the presence of MgBr2/ip-pybox.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

The mechanisms underlying the hydrolysis of methyl acetate and acetamide under acidic conditions were investigated using the MP2/6-311+G(d,p)//MP2/6-31+G(d,p) level of theory. It was necessary to include two water molecules as reactants to obtain a tetrahedral (TD) intermediate for the A AC 2 mechanism that Ingold classified for the hydrolysis of methyl acetate. This mechanism includes two TS structures, one for the formation of the TD intermediate and the other for its decomposition. Since the activation energies were calculated to be 15.7 and 18.3 kcal mol −1 , the second step determines the rate of hydrolysis. The calculated value was close to that observed at ∼16 kcal mol −1 . It was confirmed that the A AC 2 mechanism had a barrier lower by 9.9 kcal mol −1 than the A AL 2 mechanism. The A AC 2 mechanism is also applicable to the acid-catalyzed hydrolysis of acetamide. It is not the TD intermediate with which the NH 3 + moiety forms, but one further step is required to produce the final products, acetic acid and ammonium ion.

Molecular geometries of crown ether derivatives play an important role in capturing and transporting alkali metal ions such as Li + and Na + . As selectivity of the ions is observed in solution, it is necessary to know their molecular structures in solutions. Recently, we investigated stable conformations of 12-crown-O 3 N and its alkali ion complexes in aqueous and acetonitrile solutions. In the present study, we applied a procedure similar to that in previous papers to investigate the side arm effect of 12-crown-O 3 N with an amine arm for capturing Li + and Na + in the two solutions. It was confirmed that the stable structures of Li + and Na + complexes in solutions, especially the geometry of the amine side arm, are highly solvent-dependent. This conformational difference is the key to understanding the high Li + selectivity of 12-crown-O 3 N derivatives with an amine side arm in acetonitrile.

我々は、コンピュータのみを使用した合成ルートの開発を行うために、遷移状態に関する情報を収集したデータベース、遷移状態データベース（TSDB）、の構築を行っている。その過程で、ある合成ルートが他のルートより良いかを判断する時に、有機化学反応の実験収率を予測することが非常に重要であると判断するに至った。そのため、反応物、中間体、生成物に対する分子軌道（MO）計算により得られる電子状態、エネルギー、物理化学的係数等と溶媒や反応温度等の実験条件パラメータをGA-PLS法の説明変数とした検討を行った。即ち、1,4-dihydro-quinolone-3-carboxylic acid骨格を作る芳香族求核置換（SNAr）反応の収率を目的変数として、その傾向が予測できるかについて研究を行った。その中で、求核種やキノロン環の構造により説明変数が異なること、更に、特定の求核剤ではモデル化不能である等、一見、モデル化可能に見えるが、問題点が多いことを明らかにした。

Molecular geometries of crown ether derivatives play an important role in capturing and transporting alkali metal ions such as Li+ and Na+. As the selectivity of ions is observed in solutions, it is necessary to know their molecular structures in solutions. Recently, we investigated stable conformations of 12-crown-O3N and its Li+ complex in aqueous solution by the combination of three programs, the CONFLEX, Gaussian 98, and BOSS programs. In the present study, we applied the same procedure to investigate stable structures of 12-crown-O3N complexes with an alkali ion in aqueous and acetonitrile solutions. It was confirmed that the stable structures of Li+ and Na+ complexes in solutions are highly dependent on the polarity of the solvents.

The photoassisted catalytic degradation of chloroethylene was studied in a tubular photoreactor packed with TiO2 pellets prepared by a sol−gel method. The experiments were performed in a noncirculating mode. Kinetic data and the reaction products were compared with those for the photodegradation of ethylene, trichloroethylene, and tetrachloroethylene. The theoretical calculations at the MP4/6-31G**//B3LYP/6-31G** level indicated that the addition of OH radicals to chlorinated ethylenes is more exothermic than that of Cl radicals by 14.6−29.5 kcal mol-1. Examination of Cl mass balance indicated that the concentration of Cl- collected from the TiO2 surface was higher than that from the product gas stream. When the photodegradation of ethylene was performed on the TiO2 pellets which had been used for that of TCE or which were pretreated with HCl, the formation of chloroacetaldehyde was confirmed by the GC/MS. We proposed that during the photodegradation of the chlorinated ethylenes, the Cl-, as one of the re...

目的化合物の新規合成経路を創生する手段として、合成経路設計システムが既に実用化されている。このようなシステムは、一般的に複数の合成経路を提案するが、多段階で反応を考えた場合、その合成経路の数は級数的に増加し、経験豊かな合成化学者でもその選択に迷う場合がありえる。一方、提案された合成経路の存在の有無は、理論計算を用いた反応解析により、実験を行うことなしに判断することができる。さらに溶媒効果や置換基効果を考慮した計算を行えば、提案された合成経路の容易さも評価できると考えられる。これは計算化学を情報化学的に得られた未知の合成反応に適用することにより、それらの合成経路のランクづけが可能であることを示している。しかしながら、両者を融合した合成経路開発は、その有用性にもかかわらずこれまでほとんど行われていない。本研究では計算化学と情報化学を融合して、実験化学者が合成経路設計システムを利用して新たな合成経路を開発する時に有用な遷移状態データベースとその周辺プログラム、将来性について述べる。

It is possible to synthesize poly(N-substituted maleimide) by using a chiral complex consisting of a zinc and N -diphenylmethyl-1-benzyl-2-pyrrolidinoethanamine (DPhBP). The optical specific rotations [ α ] 435 25 in obtained polymers depend on the chirality of ligands in the catalysts. In the present study, density functional theory (DFT) calculations were adopted to investigate the polymerization mechanism in detail. The bulky diphenylmethyl group in the chiral ligand is effective to enhance the formation of the product in the initiation reaction. The geometry related to the pyrrolidine ring of the chiral ligand in the Zn catalyst is responsible for determining the configuration of polymers. It was also confirmed that the bulky substituent on the N atom of the N-substituted maleimide is another factor for obtaining polymers with high [ α ] 435 25 .

Stable conformations of 12-crown-O 3 N and its Li complexes in aqueous solution were investigated. To calculate the free energy differences of conformers of 12-crown-O 3 N and its Li + complex, our procedure was to make useof two programs, CONFLEX and BOSS. The former generates conformers, and the latter calculates the differences in free energy of solvation between two conformers in aqueous solution. It was confirmed that the present procedure is applicable in solving the question of what is the most stable conformation of 12-crown-O 3 N in aqueous solution. Results of the calculations suggest that the order of stability for conformers in a vacuum is different from that in aqueous solution. It was also confirmed that the coordination geometry of solvent waters to Li + changes depending on the distance between the cation and the crown ring.

An exploratory study has been carried out on new poly(aminoxyl) radicals as potential bridging ligands for 2p/3d-hybrid-spin metal complexes having network structures. Temperature dependence of the magnetic susceptibility data on the title amine N in the range 2–300 K was analyzed to show that its ground state was a doublet with a quartet state lying 559 K (=1.11 kcal mol−1) above the doublet. B3LYP/6-31G*//B3LYP/6-31G computations on a simplified model molecule (N′) confirmed the doublet ground state by 0.84 kcal mol−1. The methyl compound (C) is a triplet diradical with a singlet state lying 410 K above the triplet. The hexamethyl derivative (B′) of the title borane B has a doublet ground state with an energy gap to a quartet state by 9.9 K. The electronic structures are described qualitatively by p-(N-oxyl-tert-butylamino)phenyl homologues of (·H2C)3X in which X=N,C·, and B atoms, and carries two, one, and no π-electrons, respectively. N and B′ showed two reversible redox waves. MnII(hfac)2 and C gave a black–violet crystalline complex in which the 3d and 2p spins ordered at 60 K.

Ab initio molecular orbital calculations at the MP4(SDTQ)/6-31G∗//RHF/6-31G∗ level of theory were used to obtain detailed insight into the reaction profile on the Mg controlled 1,3-cycloaddition of nitriles oxide with allylic alcohols. It was confirmed that the complex formation reduces the HOMO–LUMO energy gaps of the two reactants. The propensity correlates well to calculated activation energies of the cycloaddition. The syn-stereoselectivity depends on the steric repulsion between the vinyl fragment and the substituent at the α-position of the alcohol or alkoxide. THF or Et2O in the reaction mixture prevent the coordination of R1CNO from forming the Mg intermediate and result in deccelerating the cycloaddition. The results obtained in the present study well explain an important role of the Mg2+ ion in the 1,3-dipolar cycloadditions of nitrile oxides with allylic alcohols.

N,N,N-Tris[p-(N-oxyl-tert-butylamino)phenyl]amine (N) was obtained as dark violet plates by lithiation of tris(4-bromophenyl)amine, followed by reaction with 2-methyl-2-nitrosopropane and oxidation of the resulting tris(hydroxyamine) with Ag2O. An X-ray crystal and molecular structure analysis of the monoclinic single crystal with space group Cc showed that it has neither C3 symmetry nor zwitterionic quinonoid structure. An EPR spectrum in MTHF solution at room temperature consisted of seven lines (aN = 4.06 G (3N) at g = 2.0058). The temperature dependence of the magnetic susceptibility data on N in the range 2−300 K was analyzed in terms of a triangular coupling model for three S = 1/2 spins to give a set of best-fit parameters which placed a doublet state as the ground state with a quartet state lying 559 K (= 1.11 kcal mol-1) above it. B3LYP/6-31G*//B3LYP/6-31G computations were performed on both spin states of a model molecule (N‘) in which all three N-tert-butyl groups in N were replaced with N-meth...

Photosolvolysis of 2-chloropropylbenzene in trifluoroethanol (TFE) produces propylbenzene, indane, 2-trifluoroethoxypropylbenzene and other solvolysis products. Propylbenzene clearly comes from 2-propylphenyl radical intermediate while the other products suggest existence of 2-propylphenyl cation as an intermediate. Density functional theory (DFT) calculations at the B3LYP/6-31G∗∗ level of theory were carried out to research reaction paths for the solvolysis products through the cationic intermediate. Three paths investigated in the present study well explain the products obtained in our experiments. The DFT calculations strongly suggest existence of the phenyl cation as an intermediate in the photosolvolysis of 2-chloropropylbenzene in TFE.

フッ素化試薬DASTによる2-ヒドロキシ-3-フェニルプロピオン酸のフッ素置換反応はフェニル基置換基の種類により２つの生成物が得られる。この反応はSN1、SN2反応の両機構で進行することが考えられ、ab inito 分子軌道計算を行い両者の反応性を比較した。SN2反応ではフェニル基置換基効果は小さく、いずれの置換基も高い反応性を示した。一方、SN1反応では中間体のフェノニウムイオン生成においてフェニル基置換基の影響を大きく受けることが明らかになった。その結果、SN2反応より置換基の関与を大きく受けるSN1で進行することが示唆された。 あわせて、フッ化物イオンを求核種とするSN2反応の検討では、中間体の脱離基SF2NEt2基はトシル基、メシル基と同等の高い脱離能を有していることが示された。

これまで経験に基づいて行われてきた目的化合物の新規合成経路を創生する手段として、合成経路設計システムが実用的となりつつある。このようなシステムは、自身が有するデータベースと推論ルーチンにより合成経路を与える。しかしながら、一般的に複数の合成経路を提案するのみで、どの経路を選択するかの最終判断は、合成を行う個々の化学者に委ねられる。もしも提案された合成経路に含まれる反応の容易さが、計算化学的手法により判断できれば、だれにでも経路のランクづけが可能となる。この問題については、遷移状態探索と極限的反応座標計算を十分に活用すれば、解決できると考えられる。本研究では、実験化学者が細かな手順に煩わされることなく遷移状態探索と反応解析を可能とするシステムの開発を行った。本システムには、遷移状態を探索する標準的な方法である、ミニマムエネルギーパス法、Saddle法、エネルギー等高線図法が組み込まれている。また、鎖状及び環状置換基を取り扱う置換基法もプログラム化されている。置換基法は既知の遷移状態構造を利用する方法で、遷移状態探索に非常に有効であることが判明した。

A substitution on 2,2-difluorovinylic carbon was investigated by using ab initio molecular orbital calculations. Three feasible mechanisms, which are the SN1-like, the SN2-type and the addition-elimination mechanisms, were ex- amined for a model borate, 2,2-difluoro-1-mesyloxyvinyl(trimethyl)borate. Four TSs were obtained depending on the position of Li+ around the vinylborate although activation energies in the gas phase are rather high (ca. 30–40 kcal mol−1) in comparison with that expected from the experimental conditions. It was confirmed at the SCRF-IPCM calculations that the solvent effect reduces the acti- vation energy of one SN2-type mechanism very much (4. l kcal mol−1 at the B3LYP/6-31+G∗//RHF/6-31+G/s* level of theory) while those for the other mechanisms do not change very much. Therefore, the SN2-type mechanism is applicable to the substitution reaction observed for the vinylborate.

A variety of armed cyclens were prepared in which ester, amide, nitrile, and pyridine moieties were attached as cation-ligating side arms to a 12-membered ring. Ester-, amide-, and pyridine-armed cyclens nicely accommodated a Na(+) ion in a three-dimensional fashion and clearly discriminated the cation from Li(+) and K(+) ions. They extracted Na(+) ion more efficiently and selectively than common Na(+) ion-selective ligands. X-ray diffraction, FAB-MS, (23)Na NMR binding studies, and computer modeling experiments demonstrated that the cyclens having ester-, amide-, and pyridine-functionalized side arms formed highly selective encapsulated Na(+) complexes via a cooperative action of parent cyclen and side arms.

The hydrolysis of esters and amides accompanies a fast reaction, which results in exchange of carbonyl 18O to 16O coming from solvent water. The present study considered two paths as the oxygen exchange mechanism. One, Path 1 called the direct path, is the mechanism that a proton of the OH fragment directly moves from the OH to the 18O fragment in the tetrahedral intermediate. The other, Path 2 called the water-assisted mechanism, is that one water molecule assists transferring a proton to make an 18OH fragment. The MP2/6-31+G* level of theory estimated rather high ΔEgas‡(TD) for the direct path of methylacetate and N-methylacetamide (21.8 and 19.7 kcal mol−1, respectively). The ΔEgas‡(H2O), the activation barrier for the water-assisted mechanism, is very low both for the ester (3.8 kcal mol−1) and for the amide (2.8 kcal mol−1). The ΔG‡(H2O) and ΔG‡(OH), calculated activation free energies including solvent effect, are small in comparison with those observed for the breakdown of TD intermediates to exchange or hydrolysis products. The present MO calculation suggests that one solvent water acts as one of the reactants and facilitates both proton transfer from the OH fragment and proton acceptance from the water to form the new 18OH fragment. It is likely that the oxygen exchange reaction accompanying hydrolysis of esters and amides proceeds via the water-assisted mechanism.

Density functional calculations at the B3LYP/6-311G**//B3LYP/6-311G level of theory were used to study the initial process of ethylene degradation on the TiO2 photocatalyst by adopting the dimeric titanium structure Ti2O6H4 as a model of the catalyst surface. Adsorption energies of water and ethylene were calculated to be 31.9 and 20.4 kcal mol−1. The photogenerated OH radical does not desorb from the catalyst surface and the further reaction with ethylene proceeds since the adsorption energy was estimated to be 39.3 kcal mol−1. Our calculation also indicated that under steady illumination, ethylene directly attacks the OH radical bound to the TiO2 surface even though the surface has vacant sites available for ethylene adsorption.

In the presence of magnesium perchlorate, 1,3-dipolar cycloaddition reactions of nitrile oxides to crotonamide bearing 4-benzyl-5,5-dimethyl-1,3-oxazolidin-2-one as the chiral auxiliary proceeded with a regio- and diastereo-selective manner to afford the corresponding chiral 2-isoxazoline. The mechanisms underlying the diastereoface selection in the cycloaddition reaction were investigated using the B3LYP/6-31G* level of theory.

In a previous paper (J. Am. Chem. Soc. 1991, 113, 4738), we reported that there was a linear relationship between the activation free energies ΔG⧧ of the Menshutkin reaction of CH3I and the proton ...

Ab initio molecular orbital (MO) study on the inversion process of six trimethylene bridges between two degenerate C 6h conformers of [3 6 ](1,2,3,4,5,6)cyclophane suggests that the inversion occurs in a stepwise manner rather than a synchronous mechanism.

The exchange interaction between two triplet carbene centers through diphenyl sulfide 4,4‘-diyl, its sulfoxide and sulfone analogs, and thiaxanthene 2,7-diyl coupling units was studied. These dicarbenes were generated by photolysis of the corresponding bisdiazo precursors in MTHF matrices at cryogenic temperatures. From the temperature dependence of the ESR signals it was found that the dicarbene jointed through the sulfide group has a quintet ground state; it serves as a ferromagnetic coupler. On the other hand, as the oxidation state or the geometry of the sulfur atom was changed to sulfoxide, sulfone, and thiaxanthene groups, antiferromagnetic interaction was observed between the two diphenylcarbene units. The magnitude of the exchange interaction J/k was determined to be 11, −30, −92, and −21 K for diphenyl sulfide, sulfoxide, sulfone 4,4‘-diyl, and thiaxanthene 2,7-diyl couplers, respectively. In the ESR spectra of sterically unconstrained sulfide and its analogs the isolated triplet signals were rat...

1,4,7,10-Tetraazacyclododecane derivatives having ester- and amide-functionalized sidearms predominantly extracted Na+ ion from an aqueous mixture of Li+, Na+ and K+ ions into a CH2Cl2 via specific octadentate complexation.

The alkaline hydrolysis of amides, N-methyl acetamide 1, acetanilide 2, and N-acetyl imidazole 3, was investigated by use of ab initio molecular orbital calculations. A detailed analysis was performed for two possible mechanisms, Path 1 and 2. Path 1, similar to ester hydrolysis, releases CH3COOH and RNH whereas Path 2 contains the RNH group that extracts the H atom from the OH fragment in the tetrahedral intermediate. In this mechanism, carboxylate ion and an amine directly form. It was ascertained that Path 2 is a better route to decompose the TD intermediate than Path 1 for 1 and 2 in the gas phase. The stability of the leaving group RNH determines which route, Path 1 or 2, is preferred in the gas phase. The solvent effect was estimated for the two mechanisms by using the SCRF calculations of the IPCM model.

A variety of double armed crown ethers were prepared in which amine, amide, ester, nitrile and pyridine moieties were attached as cation-ligating sidearms to diaza-12-crown-4 ring. FAB-MS and 7Li/13C/23Na NMR binding and liquid membrane transport studies revealed that most of them exhibited Li+ cation selectivity, though corresponding single armed lariat ethers showed Na+ cation selectivity. Among them, amine-armed diaza-12-crown-4 derivative offered the highest Li+ ion-selective ionophoric property. Its transport efficiency and selectivity were particularly superior to those of commercially available Li+ ion-selective ionophores.

The photocatalytic degradation of trichloroethylene and tetrachloroethylene in the gas phase, when porous TiO2 pellets were used, produced such undesirable chlorinated byproducts as chloroform (CHCl3) and carbon tetrachloride (CCl4). The formation of byproducts was reduced by increasing oxygen mole fractions in the feed gas stream and/or using the TiO2 pellets fired at a lower temperature. Theoretical calculations indicate that the Cl-radical-initiated reaction produces these byproducts. On the basis of the experimental and the theoretical results, a method to prevent the formation of the chlorinated byproducts is discussed.

Vibration frequencies of the NCO stretching mode were calculated for model molecules of the copper ion-exchanged ZSM-5 catalytic system, Cu(OH 2 ) 3 X n + (X = NCO, NCO − and HNCO, n = 1 or 2) by use of ab initio molecular orbital calculations. The complexes, Al(OH) 3 (NCO), Al(OH) 3 (NCO − ) and Al(OH) 3 (OCNH) were adopted as the models of the zeolite framework. According to the present calculations, the absorption bands observed at 2189 cm −1 and 2251 cm −1 are assigned to the stretching vibration of the NCO − coordinating to the copper ion and to the aluminum in the zeolite (ZSM-5) framework, respectively. This result is consistent with the experimental assignment.

The density functional calculations were performed to investigate why Li + is selectively transported by the aza-12crown-4 with an amine pendant arm. Two type of complexes, + ] and [>M + ] with four or five donor atoms coordinating to a metal, were optimized where “ + , Na + , and K + ) as the fifth ligand in [>M + ]. This result is inconsistent with that observed, i.e., only the amine arm coordinates to Li + and form [>M + ] in the solution. In order to include solvent effect in the calculations, we optimized the geometries of Li + and Na + complexes with one or two waters, [>M + ](OH 2 ) and + ] (OH 2 ) 2 , which have a cation with the hexa-coordinated environment. Only the combination of an amine arm and Li + has similar stabilization energies for formation of such complexes. The + ](OH 2 ) 2 complex releases larger stabilization energies than those for the [>M + ](OH 2 ) in the other combination of the arms and the cations.

p-Terphenoquinone analogues containing a quinonoid type of tellurophene skeleton in the central position have been prepared with a view to developing a new type of organic pnotoconductive materials having amphoteric redox properties. X-ray structure analysis showed that each molecule exhibited an asymmetric boat conformation owing to the bent structure of the whole ring system and the opposite twisting of two terminal rings. The molecular packing manner in the crystals depends on the substituents on the terminal quinonoid rings. These compounds were electrically amphoteric and afforded radical cation salts and CT complexes by electrochemical or chemical oxidation or by the reaction with an appropriate electron acceptor, respectively. Preliminary experimental results on the photoconductive properties of the neutral compound along with the electrical and magnetic properties of the radical cation salts and CT complexes are described.

Experimental and theoretical investigations of the anti-selective nucleophilic addition induced by BF 3 to 3-formyl-Δ 2 -isoxazolines are described. Ab initio molecular orbital (MO) calculations show that the 3-formyl-Δ 2 -isoxazoline-BF 3 complex prefers s-trans conformation to s-cis conformation. Nucleophiles attack the stable s-trans conformer from the opposite side of C(4) substituent, giving anti-adducts selectively. The BO bond lengths and the stabilization energies suggest that the features of the complex resemble those of aliphatic aldehyde-BF 3 complexes. Introduction of substituent to allyl tin improves the anti-selectivity from 87/13 to 98/2. These results suggest that the reaction proceeds via anti-periplanar transition state.

A systematic investigation of the cyclic ethers and amines was conducted using molecular orbital calculations to assess their possibility as building blocks of novel functional molecules. A method was developed to quantitatively calculate the Free-O and Comp-O radii which correspond to the hole sizes of free and complexed crown compounds. These radii show the linear relationship with the number of atoms in crown ring for both calculated and observed coordinates. On the other hand, the Li-X (XO and N) lengths are not dependent on the number of atoms in the crown ring. While the ΔEstab's of the crown ethers show a clear dependence on the number of the crown ring atoms, the values does not vary significantly among the cyclic amines. The MNDO method gave reasonable results by chance.

The hitherto unknown stereochemistry concerning the formation of 2,3-disubstituted cycloheptanones by the Michael addition reaction was studied. The Michael addition of thiophenol to 3-substituted 2-methylene-cycloheptanones in the presence of triethylamine in THF at ambient temperature produced 3-substituted 2-[(phenylthio)methyl]cycloheptanones with high cis selectivity (>96/4), which was unequivocally established by 1 H NMR and X-rays analyses

Reversal of enantioface selectivity was observed by merely switching the solvent from CH2Cl2 (enantiomer ratio of the adduct = 91:9) to THF (14:86) in the asymmetric Diels-Alder reaction catalyzed by the aluminum complex of a newly prepared chiral methol derivative. Negative nonlinear effect on the relationship between enantiomeric excesses of the reaction product and optical purities of the ligand was observed for the reaction in CH2Cl2 whilst linear relationship for that in THF.

Ab initio molecular orbital calculations at the MP4(SDTQ)/6-31G∗//RHF/6-31G∗ level of theory were used to obtain detailed insight into the reaction profile on the Mg controlled 1,3-cycloaddition of nitriles oxide with allylic alcohols. It was confirmed that the complex formation reduces the HOMO–LUMO energy gaps of the two reactants. The propensity correlates well to calculated activation energies of the cycloaddition. The syn-stereoselectivity depends on the steric repulsion between the vinyl fragment and the substituent at the α-position of the alcohol or alkoxide. THF or Et2O in the reaction mixture prevent the coordination of R1CNO from forming the Mg intermediate and result in deccelerating the cycloaddition. The results obtained in the present study well explain an important role of the Mg2+ ion in the 1,3-dipolar cycloadditions of nitrile oxides with allylic alcohols.

The effects of axial ligands on the ground-state geometries, electronic structures and the characteristic optical properties of iron phthalocyanine and its derivatives, FePc and FePcL(n) (L = pyridine (Py) and cyanide (CN(-)); n = 1, 2), were investigated using the density functional theory (DFT) method. The geometries of FePc with a triplet spin state and of FePc(Py), FePc(Py)(2), FePc(CN(-)) and FePc(CN(-))(2) with singlet spin states were optimized under D(4h), C(2v), D(2h), C(4v), and D(4h) molecular symmetries, respectively. The highest occupied molecular orbitals (HOMOs) of FePc, FePc(Py), FePc(Py)(2), and FePc(CN(-)) are pi-type orbitals, which have no contribution from the p(z) atomic orbitals of all nitrogen atoms, whereas the HOMO of FePc(CN(-))(2) is the 7e(g) orbital, which has contributions from the d(xz) and the d(yz) orbitals of the Fe atom mixing with the pi-orbitals of the axial CN(-) ligands. The time-dependent (TD) DFT method gives many optically allowed excitations for FePc, FePc(Py), FePc(Py)(2), FePc(CN(-)), and FePc(CN(-))(2) in the UV-VIS region. Our calculated bands corresponded well with the experimental results. In FePc(Py)(2), the metal-ligand charge transfer (MLCT) transitions from the metal d to the axial-ligand pi*-type orbitals contributed to the B band region. In FePc(CN(-))(2), the MLCT transitions from the metal d to the Pc-ring pi*-type orbitals contributed mainly to the first B band region, but those from the metal d to the axial-ligand pi*-type orbitals did not appear in the energy regions of the Q and B bands. Thus, the axial ligands caused a spectral change in FePc through orbital mixing.