An imaginary transition structure (ITS) is defined as a kind of structure that has par-, out-, and in-bonds in accord with structural changes during an organic reaction. Various subgraphs (or substructures) of an ITS afford effective pieces of information on reaction types. Thus, imaginary rings in an ITS are the descriptors of ring-opening, ring-closure, and rearrangement reactions. Three- and four-nodal subgraphs correspond to reaction-site changes. Other useful concepts such as reaction-center graphs, reaction graphs, and reaction strings are also discussed. An algorithm for selecting an essential set of essential rings is proposed. The first method for giving a canonical name to ITS is presented. Enumeration of reaction types is also discussed.
Recent developments in the synthesis of 2-pyrone and 2-pyridone derivatives by the reaction of ketene dithioacetals with active methyl or methylene compounds are summarized by major emphasis that is placed on the results obtained in our own laboratory. The reaction of 4-methylthio-2-pyrone or 2-pyridones with various nucleophiles such as amines or active methylene compounds is also described.
This review deals with the most recent utilization of bismuth and bismuth compounds in organic synthesis : (1) mild and selective oxidation of alcohols using organobismuth (V) reagents, (2) mild and efficient phenylation on carbon, nitrogen, and oxygen using organobismuth (V) reagents, (3) chemo- and stereoselective allylation of aldehydes using Bi (0) or BiCl3, and (4) other carbon-carbon bond forming reactions and miscellaneous reactions utilizing bismuth compounds.
The reactions of arene- and methanesulfonyl chlorides with alkenes catalyzed by dichlorotris(triphenylphosphine)ruthenium (II) were found to give 1 : 1 adducts in high yield. Whereas, trichloromethanesulfonyl chloride added to alkenes with extrusion of sulfur dioxide under similar conditions. A reaction mechanism involving a radical intermediate which interacts to the ruthenium in the coordination sphere is proposed. The reactions of styrylsulfonyl chloride with alkenes under similar conditions afforded 1 : 1 adducts at the initial step, then followed dehydrochlorination and desulfonylation from the adducts successively to give divinyl sulfones and 1, 3-butadienes in high yield, respectively. The reaction is a novel and convenient methods for synthesis of substituted 1, 3-butadienes. The reactions of alkane- and arenesulfonyl chloride with alkenes in the presence of a catalytic amount of ruthenium (II) complex with chiral ligand, Ru2Cl4 [(+)-DION]3 or Ru2Cl4- [(-)-DION]3', were found to give optically active adducts with about 10-40 % e.e. These results suggest that radicals formed by the interaction with metal catalysts are coordinated with metals, and therefore such reactive species should be called “RADICALOID” since carbenes coordinated to metals are called carbenoid.
Anionic living polymerizations of monomers with functional silyl groups are reviewed. The monomers include styrenes and 1, 3-butadiene derivatives containing Si-OR, Si-NEt2, Si-H, Si-O-SiMe3, Si-SiMe3, Si-CH2-CH =CH2, and Si-CH =CH2. The polymerizations of these monomers with anionic initiators such as butyllithium, alkali-metal naphthalenides and oligo (α-methylstyryl) dialkali-metal salts, always proceed without chain transfer and termination reactions to afford stable living polymers, although the limited conditions are required in some cases. The polymers with controllable molecular weights and narrow molecular weight distributions (Mw/Mn≤ 1.1) are obtained in all cases described here. Synthesis of new types of block copolymers with styrene. isoprene with these monomers are also discussed.
Nonlinear optical materials, which are expected in various applications such as optical information processing, telecommunication, integrated optics, etc., have aroused our interest. Among many organic nonlinear optical materials which are considered to have a number of merits compared with inorganic ones, 2-methyl-4-nitroaniline (MNA) is one of the most famous compounds. This compound, however, has an insufficient transparency in blue light region, making MNA inadequate for a frequency doubler for blue light generator. Our study for finding compounds with higher transparencies for blue light resulted in 1- (4-nitrophenyl) azole derivatives and 5-nitrobenzazole derivatives. When compared from the viewpoint of the second order molecular hyperpolarizability (β) calculated by PPP-CI method, the 1- (4-nitrophenyl) azole derivatives were judged better than 5-nitrobenzazole derivatives.