This review deals with the application of fluorine-containing heterocycles as biological active compounds and functional material. Various approaches to the four-, five-, and six-membered heterocycles and the relative compounds bearing fluorine atom or trifluoromethyl group are summarized and the synthetic methods are mainly depending on cyclization of the fluorinated building blocks.
Recently, we have proposed a new designing concept, “Respective Control Concept”, for developing highly efficient chiral bisphosphine ligands. On the basis of our concept, new chiral bisphosphine ligands, BCPM, MOD-BPPM, MOD-DIOP, etc. have been synthesized. Their rhodium complexes have been found to show very high catalytic activity and enantioselectivity in the asymmetric hydrogenations of prochiral carbonyl and olefinic compounds. Practical asymmetric syntheses of useful biologically active compounds have been realized by using these hydrogenations as key reactions.
Steroids are one of the most interesting and the most widely distributed and also one of the most structurally complex families of naturally occurring substances. Due to their great importance for biology and medicine, intensive efforts have been devoted into their synthesis. Especially, stereoselective construction of steroidal side chains has been the subject of extensive synthetic efforts, because their physiological activity has been reflected in the stereochemistry of the side chain. This article describes the highly stereoselective construction of steroidal side chains, where furan and its analogues are employed as the carbon-unit sources of the side chains. Moreover the strategies developed above are applied to the synthesis of several natural products, such as brassinolide and ecdysone.
An economical synthetic process of methyl jasmonate has been established. Total yield of this process is higher than 60 % for all five steps from cheaply available adipic acid. 2-Pentyny1-2-cyclopentenone, the key intermediate in this route, is synthesized by applying the improved palladiumcatalyzed enone formation from allyl β-keto carboxylate as a key reaction. The pentynyl moiety is introduced by the use of pentynyl chloride which is prepared in two steps from 2-butyne, our original source, cheaply.
Photochemical reduction of nitroaromatic species has been critically reviewed. The photoreaction mechanism of nitroaromatic compounds has been less understood in comparison with that of aromatic carbonyl compounds, because the properties of nitroaromatic excited states are still ambiguously described. At least three different lower electronically excited states are involved in the longest wavelength absorption band. These are La (long-axis polarization), Lb (short-axis polarization), and nπ* states. The relative location of these three states is dependent upon the nature of substituents and solvents, and therefore the characterization of lower excited states of nitrobenzene derivatives are rather difficult. Since complications due to the secondary process of primary photoproducts are inevitable, an intermolecular photoreduction for nitroaromatic species is practically of minor importance. On the other hand, some intramolecular photoredox reactions involving ο-nitrobenzyl moiety have been used for photosensitive protection of a certain functional group and photoresists.