According to a system of classification for multi-stage redox systems proposed by Hünig, tetrathiafulvalene (TTF), bithiopyranylidene (BTP) are considered to be Weitz-type donors whereas tetracyanoquinodimethane (TCNQ) is regarded as Wurster-type acceptor. Recent efforts to explore new redox systems have provided various structural modifications, such as symmetrical, unsymmetrical, condensed, and inserted versions on TTF, BTP, and TCNE. In this review recent progress in design and synthesis of the modified TTF, BTP, and TCNE systems is described.
The recent discovery of the new family of compounds, named leukotrienes because of their origin from leukocytes and a structural characteristic, the conjugated triene, has significantly increased our knowledge of arachidonic acid metabolism. This review will focus on the chemistry leading to the complete stereochemical elucidation of the leukotrienes, as well as more recent synthetic advances.
Effects of the structure of diphosphines, especially of n in Ph2P (CH2) nPPh2 (PnP), on the structure, reactivity, catalytic activity and selectivity, and asymmetric induction ability of transition metal complexes are described. The catalytic activity and selectivity change variously depend on n when PnP are used with catalyst metal complexes. P2P is suitable when chelating species is active, while P3P or P4P is superior when dissociation of the diphosphine is necessary. In asymmetric reactions, the diphosphines which form rigid coordination structure bring about high optical yield.
Electrophilic perfluoroalkylations have been scarcely reported, though they are of great importance for introduction of perfluoroalkyl groups to organic compounds. It was found that FITS-m (m=10-2, 3i), synthesized by the reaction of bis (trifluoroacetoxy) -or difluoroiodoperfluoroalkaneswith benzene and trifluoromethanesulfonic acid, acted as highly reactive electrophilic perfluoro.alkylating agents. FITS underwent the first electrophilic reactions with carbanions, alkenes, alkynes, etc., and afforded many synthetic methods for perfluoroalkylated compounds, of which preparationswere difficult by the conventional, free radical or nucleophilic reactions. Studies on the reactivity of FITS led to fortultous discovery of oxy_perfluoroalkylation, a newtype of oxygenation, which made it possible. to prepare perfluoroalkylated carbonyl compoundsdirectly from alkenes under oxygen atmosphere. Effective use of the fluorine atoms in the perfluoroalkyl groups as an application of FITS-2 or 3i provided a new synthetic approach to trifluoromethyl-compounds with various functionalgroups.