In this article are reviewed some special topics for the synthesis of cyclic peroxides ; (a) a survey for the synthesis of 1, 2-dioxolanes, a model of prostaglandine endoperoxide, (b) synthesis of cyclic peroxides by a process involving single electron transfer, (c) peroxyzwitter ions and diradicals as the key intermediates in the synthesis of cyclic peroxides, and (d) peroxy intermediates participating in ozonolysis and related reactions.
Novel electron acceptors and donors containing fused-heterocycles such as 1, 2, 5-thiadiazole, 1, 2, 5-selenadiazole, and pyrazine were synthesized and their properties including those of their charge-transfer complexes or ion-radical salts were investigated in detail. Tetracyanoquinodimethane (TCNQ) derivatives fused with those heterocycles show interesting properties which are not found in TCNQ itself due to the heterocycles which can accept negative charge and increase intermolecular interactions by heteroatom contacts. Quinones fused with sulfur heterocycles are stronger electron acceptors than chloranil. Bisthiadiazolopyrazine, a 14 π hypervalent heterocycle, have extremely high electron affinity. Tropylium ions fused with heterocycles gave highly conducting TCNQ_??_ salts. Tetrathio-derivatives of p-quinodimethanes fused with electron withdrawing heterocycles are colored electron donors in which on-site Coulomb repulsion is decreased. Dimethyldihydro [1, 2, 5] thiadiazolo [3, 4-b] pyrazine is also a new type of electron donor whose oxidation potential is very low due to a 12 π electron ring system.
Some acyclic rigid compounds which bearing phenyl and hydroxyl groups were found to be good host compound. On the basis of this finding, we designed several new host compounds. Some optically active hosts were also designed. These hosts form crystalline inclusion compounds with a wide variety of guest compounds in which efficient and precise molecular recognition are observed. Application of the molecular recognition to isolation of compound in pure state from a mixture, isolation of water soluble material from aqueous solution, and isolation of natural product were studied. Optically active host includes one enantiomer selectively. By using the enantioselctive inclusion, optical resolution of some racemic guests were achieved efficiently.
The following novel organic syntheses using group VIII metal complexes, especially iron, rhodium and ruthenium, which have been disclosed by the authors are reviewed. 1) Highly selective reduction and carbonylation of a wide variety of organic compounds using alcoholic potassium tetracarbonylhydridoferrate (KHFe (CO) 4 (1)) as a reagent. 2) N-Alkylation and N-heterocyclization using amines and aldehydes mediated by 1, which provides novel synthetic methods for quinolines, benzimidazoles, isoindoles and isoindolines. 3) Rhodium and ruthenium catalyzed N-alkylation and N-heterocyclyzation of amines which involve the activation of N-H and O-H bonds. 4) Synthesis of aldehydes and ketones using K2Fe (CO) 4 reagent or ruthenium catalysts. 5) Ruthenium complex catalyzed novel carbon-carbon bond forming reactions using formyl derivatives which involve the catalytic activation of formyl C-H bond. 6) New methodology for carbonylation of alkyl iodides having β-hydrogens on saturated sp3 carbons is explored. Photo- and electrochemical carbonylations using various group VII and VIII metal complexes smoothly proceed under extremely mild conditions (i.e., at room tempeature and under 1 atm of CO (balloon)). The mechanisms of these novel reactions are suggested.
For the purpose of synthesizing effectively the optically active natural products which contain a long chain consisting of many consecutive chiral carbon atoms, it is indispensable to realize the highly diastereoselective connections between the selected chiral segments. “Two-stage coupling process” is one of the solutions, It consists of the first stage (stage I) of addition reaction of chiral vinyllithium compounds to 2-methyl-substituted aldehydes and the second stage (stage II) of homogeneous hydrogenation of exo-methylene group in the major Cram (syn) type of addition products with Wilkinson's catalyst. This article describes the mechanism of diastereoselective first stage of this process on the basis of the conformational analysis of transition states and the successful application of this process to syntheses of macrolide antibiotics.
Rifamycins are important antibiotics. This article describes the studies on rifamycins; i) the formation of dihydropyrimidorifamycins in the reaction of rifamycin S with hexahydro-1, 3, 5-triazines, ii) the formation of dihydropyrimidorifamycins from 3-formylrifamycin S and 3-formylrifamycin SV, iii) the reduction of the iminium bond of dihydropyrimidorifamycins, and iv) the reaction of 3-formylrifamycin S with Schiff bases and aminomethylethers.