When electron transfer from a nucleophile (reductant) to an electrophile (oxidant) is energetically feasible, the electron transfer precedes a polar pathway to produce a radical ion pair, which leads to the final products via the follow-up steps involving cleavage and formation of chemical bonds. The follow -up steps are usually sufficiently rapid to render the initial electron transfer the rate-determining step in an overall irreversible transformation. The rate-determining electron transfer step can be accelerated by a catalyst which can interact with one of the electron transfer products. Both thermal and photochemical redox reactions which would otherwise be unlikely to occur are made possible to proceed efficiently by the catalysis on the electron transfer steps. The fundamental concepts of catalysis on electron transfer are presented and the mechanistic viability is described by showing a number of examples of both thermal and photochemical reactions that involve catalyzed electron transfer processes as the rate-determining steps.
Two types of reactions with organomanganese have been examined. The first is a reaction of manganate reagents with carbon-carbon multiple bond. Catalytic version of these reactions is also disclosed. The second is a reaction of gem-dibromo compounds such as gem-dibromocyclopropane and dibromomethyltrialkylsilane with trialkylmanganate (II). The reaction was initiated by bromine-manganese exchange.
Novel methods for the oxidation of alkanes with molecular oxygen using a radical catalyst, N-hydroxyphthalimide (NHPI), have been developed. Thus, a variety of alkanes such as cyclohexane, adamantane and toluene which are very difficult to be oxidized with molecular oxygen by conventional methods could be converted into the corresponding alcohols and/or carbonyl compounds in high yields. The application of the same methodology to adamantane with CO/air led to adamantanecarboxylic acid through radical carbonylation in fair yield. The reaction of benzyl ethers with NO in the presence of NHPI afforded the corresponding aldehydes in good yields. The present method provides a new class of aerobic oxidation which is refered to as radical-catalyzed autoxidation.
The effect of Endocrine Disrupting Chemicals (EDCs) upon an organism is mainly mediated by its own hormone receptors and the signal transduction systems linked to them. This leads to a scientific assumption that EDCs can affect the host in a very low concentration as the intrinsic hormones can do, and EDCs may affect multiple signaling systems and may cause an interaction with other signal transduction systems, resulting in antagonistic, additive, or synergistic effects. Our current scientific assumption would be that the effects of EDCs on an adult organism may be subtle. The established homeostatic mechanism will limit them to reversible responses. On the other hand, the developing organism may be influenced by the EDCs in a irreversible way (for example, malformations or hypogenesis of organs). The hormonal systems critically control certain steps of the development of the fetus. Unfortunately, the knowledge of the mechanism related to hormone regulations on embryogenesis is not sufficient to assess the possible adverse effects caused by EDCs on organism in that state. That is why we have to further investigate this issue not only from the chemical side but also from the basic biological side to fully understand the molecular interactions taking place in our body.
This review deals with the problem on “Endocrine Disrupting Chemicals”, which has recently been argued as one of serious matters on the effect to human being as well as to environment. Dr. Theo Colborn and other co-authors discussed extensively on these substances as endocrine disruptors or endocrine disrupting chemicals by their monograph “Our Stolen Future”. In Japan, however, these terms are erroneously translated as “(So-called) Environmental Hormones” in the author's opinion. Thus, the author discusses the terminology in science first, and then, to manufacture useful materials and products tolerant to environment. As a typical example, the manufacture and the use of pesticides and the effect to agricultural production and environment are described perspectively.
Some exogenous chemicals such as PCB, tributyltin compounds (TBT), and diethylstilbestrol (DES) are reported to disrupt the action of the sex hormones, thus resulting in unexpected biological effects. The manufacture and use of these chemicals have strictly been restricted in Japan. Bisphenol A and nonylphenol are suspected to be endocrine disrupter. However the both phenol chemicals are degradable in the environment and far less toxic than PCB, TBT and DES. Environmental pollution with chemical substances are reported to be getting serious every year by mass media. However it peaked around 1970 and has been improved evidently since that. This report deals with the overall evaluation of the endocrine issue in Japan.