巻号一覧
50 巻, 8 号
選択された号の論文の8件中1～8を表示しています
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一電子移動効率とN-Mg, C-Mgの諸反応の体系化大久保 正夫, 松尾 浩二1992 年 50 巻 8 号 p. 682-691
発行日: 1992/08/01
公開日: 2010/01/28
ジャーナル フリーAryliminodimagnesium (ArN (MgBr) 2, IDMg) reacts with various kinds of substrates in the modes of condensation, addition, replacement, and coupling. Many reactions of this N-Mg and also C-Mg (Grignard) reagents were classified in terms of “efficiency of single electron transfer (SET)” using the difference between oxidation and reduction potentials of reactants (ΔE=Eox-Ered). The minor factors disclosed from detailed distribution of normal and abnormal products are those arising from “aggregation of excess reagent molecules” and from “σ-complexation of reactants”. The former factor participates in common to the N-Mg and C-Mg reactions of medium ΔE, whereas the latter factor participates in common to three reactions of large ΔE using N-Mg which is weakly electron-donating. Usefulness of the ΔE-approach for structure-reactivity study and also synthetic use of various magnesium reagents were discussed.抄録全体を表示PDF形式でダウンロード (1376K) -
〓原 徹1992 年 50 巻 8 号 p. 692-702
発行日: 1992/08/01
公開日: 2009/11/16
ジャーナル フリーBy the use of appropriate model compounds, semiempirical molecular orbital calculation could reproduce the following experimental results :
1) the stereoselectivities observed in addition reactions of methanol and 1, 3-dioxolanyl radical to 3-C- and/or 2-C-nitro-2-enopyranoside derivatives,
2) the higher kinetic acidity of the anomeric, quasiequatorial proton than the alternative one of 1, 5-anhydro-3-C-nitro-2-enitol derivative,
3) chlorination of 1, 5-anhydro-3-C-nitro-1-enitol derivative in various ethers.抄録全体を表示PDF形式でダウンロード (1224K) -
斎本 博之, 重政 好弘1992 年 50 巻 8 号 p. 703-712
発行日: 1992/08/01
公開日: 2010/01/28
ジャーナル フリーOne-pot synthesis of saccharides and their derivatives from formaldehyde is called “Formose Reaction”. The formose reaction consists of (1) benzoin type condensation of aldehyde, (2) aldol and retro-aldol reaction, (3) enediol rearrangement and epimerization, and (4) Cannizzaro and cross-Cannizzaro reaction. In this review were described recent progresses in improvement of product selectivity, isolation of formose sugars, thiazolium salts-catalyzed benzoin type condensation, and aldol condensation in an aqueous phase. Identification of formose sugars revealed a reaction pathway to lead 2, 4-bis (hydroxymethyl) -3-pentulose. Formation of ribose was discussed in connection with the origin of ribonucleic acids.抄録全体を表示PDF形式でダウンロード (796K) -
-テルペノイド合成の一断面-萩原 久大1992 年 50 巻 8 号 p. 713-725
発行日: 1992/08/01
公開日: 2010/01/28
ジャーナル フリーThe kinetic enolates or trimethylsilyl enol ethers of 1-acetylcyclohexene undergo successive double Michael reactions with α, β-unsaturated carbonyl compounds to give substituted decalones. The kinetic enolates of cyclohexenone provide bicyclo [2.2.2] octane derivatives via double Michael reaction. These double Michael reactions have been extended to bicycloannulation leading to tricyclo [4.4.0.01.5] decane or tricyclo [3.2.1.02.7] octane compounds by employing α-bromo-α, β-unsaturated esters with cyclohexenone or 1-acetylcyclohexene, respectively. Divinylketone and the trimethylsilyl enol ethers of cyclohexenone undergo Lewis acid assisted triple Michael reactions yielding tricyclo [5.3.1.03.8] undecane derivatives. These successive multifold Michael reactions have enabled the synthetic studies of ε-cadinene, khusitone, khusilal, isoeremolactone, ishwarane, and seychellene.抄録全体を表示PDF形式でダウンロード (1341K) -
穐田 宗隆, 諸岡 良彦1992 年 50 巻 8 号 p. 726-736
発行日: 1992/08/01
公開日: 2010/01/28
ジャーナル フリーMechanisms of syngas reactions which produce a wide variety of organic compounds including hydrocarbons and oxygenates and consist of multi-step elementary transformations have been studied by employing organometallic model compounds. Since the three plausible reaction mechanisms proposed on the basis of previous catalytic studies may be recognized as combinations of two reaction stages, that is, (1) reduction of coordinated CO into CHx and CHxO species and (2) carbon-chain elongation step, model reactions have been reviewed according to the two aspects. In addition, results of the reduction of organometallic compounds using hydrosilanes or hydrostannanes in place of dihydrogen are also briefly summarized. Such reducing agents turn out to be effective for the reduction of oxygen-containing intermediates and, as a result, new model systems for production of alkanes, alcohols, aldehydes, and ethylene have been established.抄録全体を表示PDF形式でダウンロード (1540K) -
柳 日馨1992 年 50 巻 8 号 p. 737-745
発行日: 1992/08/01
公開日: 2010/01/28
ジャーナル フリーA novel carbonylation method based on free-radical reactions has been developed. Acyl radicals, generated by the addition of alkyl free-radicals to carbon monoxide, have been effectively trapped by tin hydride. Through this sequence, the free-radical formylation of organo halides to the corresponding aldehydes was realized. Carbonylative cyclizations to give cyclopentanones can also be affected starting with 4-pentenyl halides. When an alkene was also present in the reaction system, the trapping of the alkyl free-radical by carbon monoxide to form an acyl free-radical and the subsequent addition of that radical to the alkene took place efficiently to give an unsymmetrical ketone. This sequence represents a unique method for the double alkylation of carbon monoxide β, γ-Unsaturated ketones can be synthesized via a three-component coupling of alkyl iodides, carbon monoxide, and allylstannane. All of these findings have demonstrated that free-radical carbonylation is a useful method for the introduction of carbon monoxide into organic molecules.抄録全体を表示PDF形式でダウンロード (880K) -
北川 敏一, 竹内 賢一, 小松 紘一, 木下 知己1992 年 50 巻 8 号 p. 746-757
発行日: 1992/08/01
公開日: 2009/11/16
ジャーナル フリーTwo novel classes of hydrocarbons, i.e. hydrocarbon salts and ionically dissociative covalent hydrocarbons, were prepared from Kuhn's carbanion (5-) and various cyclopropenylium and tropylium ions.
The ionic structures of the hydrocarbon salts were evidenced by IR spectra (solid state), UV-vis spectra (DMSO), and electric conductivity measurements (DMSO) The salt obtained from 5- and tricyclopropylcyclopropenylium ion formed a unique covalent compound in chloroform which can exist only in solution. The salt of 5- and tricyclopropyltropylium ion was found to undergo both coordination and single-electron transfer in THF, affording a yet unknown type of equilibrium system, in which the ionic, radical, and covalent species coexist.
Studies on the free energies of heterolysis of the newly synthesized covalent hydrocarbons revealed the importance of the steric effect in the heterolytic cleavage of σ carbon-carbon a bond. It was also found that a slight difference in the cation stability differentiates the product, either ionic or covalent, of the reaction with a carbanion.抄録全体を表示PDF形式でダウンロード (1466K) -
〓原 徹, 萩原 久大1992 年 50 巻 8 号 p. 758
発行日: 1992/08/01
公開日: 2009/11/16
ジャーナル フリーPDF形式でダウンロード (144K)
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