Characteristic properties of organosulfur compounds bearing azaheteroaromatics and their applications for organic synthesis are described as follows : 1) strategies for development of new synthetic procedures by using thione-thiol tautomerisms of pyridyl derivatives. 2) studies on new ligand coupling reactions of benzyl pyridyl and related sulfoxides with Grignard reagents and butyl lithium together with their stereochemistry and mechanisms. 3) preparation and reactions of pyridyl and quinolyl Grignard reagents. 4) ipso-substitution reactions on the azaaromatic compounds bearing sulfinyl and sulfonyl groups with nucleophiles.
Synthetic peptide lipids having amino acid residue (s), interposed between a polar head moiety and a hydrophobic double-chain segment as hydrogen-bonding component (s), constitute morphologically stable bilayer membranes in aqueous media. Relevant adjustment of the packing mode of lipid molecules results in the formation of nonbilayer structures, inverted cubic and hexagonal phases, which have been assumed as key intermediates in the membrane fusion, and these phases are evidently involved in the present dynamic fusion processes. Single-walled vesicles formed with the present peptide lipids are utilized as effective apoenzyme models for formation of artificial holoenzymes with various hydrophobic coenzyme models of NADH, vitamin B6, and B12.
Practical and stereocontrolled new methods for the synthesis of highly potent synthetic pyrethroids, 2, 2-dimethyl-3- (2-chloro- 3, 3, 3- trifluoro- 2- propenyl) cyclopropanecarboxylates are described. The key of the methods is the transformation of RCHO to RCH=C (Cl) CF3. This was achieved (1) by aldehyde addition of a zinc carbenoid CF3CCl2ZnCl prepared from CCl3CF3 and Zn, followed by acetylation and reduction; (2) by one-pot procedure using CF3CCl3/Zn (> 2mol) /Ac2O (1mol); or (3) by conversion to RCH (OH) CX = CF2 with CF3CCl3/Zn (> 2mol) /AlCl3 (cat.) followed by regio- and stereoselective fluorination. Application of these to 3- formyl- 2, 2- dimethycyclopropanecarboxylates afforded the trans isomer of the target compounds. A series of transformation involving addition of CF3CCl2ZnCl to 3- methy- 2- butenal, conversion into Me2C = CHCH (COCHN2) CCl2CF3, intramolecular carbene addition, and reduction gave the cis acid of the aimed pyrethroids.
Solid-acid catalysts having sulfo groups were prepared by two different ways. One way is by surface modification of silica. The other is by the sulfonation of polyorgano-siloxanes. Polysiloxanes containing phenyl, benzyl, 2- (phenyl) ethyl, and 3-mercaptopropyl groups were prepared by co-condensation polymerization of alkoxysilane and alkoxyorganosilane. The ion exchange capacity and the elemental analysis for sulfur and carbon showed that the sulfonated polyorganosiloxanes (SPOS) had much higher acid content (0.8-3.2mmol/g) than the modified silica gel. The thermal stability of SPOS was much higher than Amberlyst 15. Thus, the thermal stability is in a decreasing order; sulfonated polyphenylsiloxane>sulfonated polypropyl-siloxane>Amberlyst 15 under a nitrogen stream, and is in a decreasing order; sulfonated polypropylsiloxane>sulfonated polyphenylsiloxane=Amberlyst 15 under steaming conditions. The catalytic activities for various acid-catalyzed reactions were studied. For vapor phase dehydration of alcohols and the liquid phase esterification, the activities of SPOS were comparable to those of Amberlyst 15. For the vapor-phase nitration of benzene with nitrogen dioxide, the activities of SPOS were much higher than that of the ion-exchange resin.
New syntheses of a variety of heterocycles using two kinds of ketene-S, N-acetals (KSNA) are described. KSNA derived from thioamides are regarded as interesting enamines (A : α-alkylthioenamines B : lithioenamines). Their utilities as synthetic intermediates to heterocycles are presented.
Process, catalyst, and reaction mechanism for vinyl acetate synthesis have been reviewed. Progress and improvement are discussed in the following sections, (1) acetylene-based process, (liquid- and vapor-phase) (2) ethylene-based process, (liquid- and vapor-phase) (3) carbon monoxide-based process, and, as additional item, (4) newer ethylene synthesis from methane comprised in dry natural gas.