Hydrosilanes are compounds with active Si-H bonds and can be used as effective building blocks for synthesizing organic silicon-containing materials through metal-catalyzed hydrosilylation of olefinic substrates. Recently, novel transition metal-catalyzed cross-coupling reactions of aryl and heteroaryl compounds with hydrosilanes have been reported. These reactions proceeded efficiently under mild conditions, and in most cases arylated products were obtained in good to high yields with good functional group tolerance. This review presents the recent results of these research activities with respect to effective catalytic methods for the preparation of arylsilanes using hydrosilanes as silicon sources.
Since the synthesis of the first pentacoordinated organophosphorus compound, Ph5P, by Wittig, the chemistry of pentacoordinated phosphorus compounds has been extensively expanded. Pentacoordinated phosphorus compounds usually take a trigonal bipyramidal structure with two distinctive sites; apical and equatorial positions. In the trigonal bipyramidal structure, electronegative and small substituents prefer the apical positions. Such properties are widely recognized as the apicophilicity rule. However, several examples breaking the apicophilicity rule have been reported in the past few decades and novel properties and reactivities of these new classes of compounds have been found. In this review, the synthesis of novel pentacoordinated phosphoranes with anti-apicophilic arrangement will be introduced, as well as their structures, spectroscopic properties, and reactivities.
Nucleoside antimetabolites act an important role in the fields of cancer and viral chemotherapies. To search new agents effective for tumor and virus, many attempts were made for synthesizing novel nucleoside derivatives. Construction of the glycosidic bond is a key reaction to synthesize new nucleoside derivatives. We have been focused the synthesis of novel biologically active nucleoside derivatives by developing novel “glycosylation” reactions. Our first successful example was the synthesis of 4′-thionucleoside by using the Pummerer-type thioglycosylation reaction. As a result, we found potent antineoplastic nucleoside, 4′-thioFAC, and some novel 4′-thionucleosides possessing antiherpes virus activities. Secondary, we developed a new entry to isonucleosides in which the Mitsunobu reaction with neighboring sulfur assistance was employed as a nucleobase introducing reaction. We also developed a conceptually new method for synthesizing carbocyclic nucleosides based on hypervalent iodine chemistry. The mechanism of this oxidative coupling reaction was investigated.
Solution-phase organic synthesis on soluble tags has developed as an alternative to the heterogeneous resin-supported and combinatorial methodologies. Efforts to design the tags have led to investigation of the effects of high reactivity of the soluble species and the possibility of using routine analytical methods (NMR, TLC, MS, etc.). In particular, hydrophobic tag strategies have been recognized as useful methods which result in effective generation of target products. Towards the separation of tagged products, liquid-liquid extractions (LLE) may also have broad potential, because suitably tagged compounds in a biphasic system often show particular affinity for one phase without further supports. A recent study opened the door to the use of thermomorphic systems which can be applied in the form of a recyclable catalytic system in palladium- catalyzed cross-coupling and other reactions. In this paper, our recent research on the construction of cycloalkane-based thermomorphic solution systems with the hydrophobically tagged compounds. Organic reactions in homogeneous organic solutions, the reaction mixture gave the phase-separation just by cooling or addition of organic solvents. Desired products were immediately separated as a cycloalkane solution that could be successively used for following multi-step reactions. The biphasic solution system has been applied for electrochemical reactions, multi-step peptide, oligo-saccharide, and glyco-peptide syntheses featuring multi-step rapid and efficient reaction/separation process.
Maxacalcitol (OCT) (1), the 22-oxa-derivative of 1α, 25-dihydroxyvitamin D3, has been discovered as a promising candidate for the treatment of antihyperparathroidism and antipsoriatic by our medicinal chemistry research team. In order to enable the development, our process research group has made efforts for its practical large-scale production which allowed successful launch of OCT (1) as an antihyperparathroidism agent in 2000 and as an antipsoriatic agent in 2001. This article describes aspects of the efforts of the process research team making the present industrial production of OCT (1) possible on the basis of the initial synthesis carried out by the medicinal research group.
We have studied the development of functionalized ionic liquids and control of cation-anion interaction in ionic liquids. Herein we report that utilizing a functionalized ionic liquid with a sulfonate group enable us to carry out greener porphyrin syntheses than ever. Such an ionic liquid shows an effective reactivity and a green property by working as an acidic catalyst which is separated from the reaction medium. Moreover, the specific solvation behaviour in ionic liquids was investigated in order to effectively apply the ionic liquids for various reactions. We have found out that [C4mim] [CS] composed of a bulky camphorsulfonate as an anion provides a ionic liquid. The ES-MS analyses of it revealed a loose interaction between the C4mim+ and the bulky CS-. The [C4mim] [CS] produced an effective endo/exo stereoselectivity in the Diels-Alder reaction. The loose cation-anion interaction of [C4mim] [CS] produces a more naked C4mim+. Therefore the naked C4mim+ can more readily contact the reactant further than its counter-anion. The ES-MS analysis directly demonstrated these interactions.
Hydroaminoalkylation of alkenes, where the α-C–H bonds of N-alkylamines are added to alkenes, is one of the unique strategies for functionalization of both amines and alkenes. This review introduces the recent developments of the catalytic, intra- or inter-molecular hydroaminoalkylation, as well as the mechanistic studies on that.