Recent progress in chemistry on ruthenium complexes is reviewed from a viewpoint of homogeneous ruthenium complex-catalyzed organic synthesis. Some real active intermediary species of the ruthenium complex-catalysis are isolated from the catalytic reaction mixtures or their model complexes are synthesized by stoichiometric methods. This article deals with the following subjects : (i) Progress on the ruthenium (II) -BINAP complexes which exhibits higher activity and stereoselectivity in catalytic asymmetric hydrogenation, (ii) Ruthenium (II) complex-promoted activation of some organic compounds such as alkenes, alkynes and nitriles, forming various types of complexes with the activated ligands, (iii) Relationship between the active ruthenium (0) complexes and the ruthenium-catalyzed C-H activation.
In the presence of SnCl4-Bu3N reagent, silyl enol ethers and ketones were α-alkylidenated or α-alkenylated with 1-alkynes. Phenols were ortho-alkenylated using this system. Direct ortho-vinylation of phenols was achieved by treating with ethyne (acetylene gas) at ambient pressure. These syntheses involve carbostannylation reaction where α-stannyl ketones or phenoxytins add to alkynyltrichlorotins giving 1, 1-bis (stannyl) alkenes.
Ionic olefins are adsorbed on oppositely charged surface consisted either of molecular aggregates of organic surfactants or inorganic clay interlayers. The ionic olefins, i.e., stilbazolium cations and unsaturated aromatic carboxylate anions, undergo efficient and stereoselective photocyclodimerization in the present heterogeneous reaction fields. The reaction pathways are quite different from those in solution, where no cyclodimers formed and, observed is only E-Z photoisomerization. Employed are not only micelle, reversed micelles, and vesicles as organic interface, but also montmorillonite and hydrotalcite clays as inorganic minerals. The stereochemistry of the resulting cyclodimers has been elucidated to be controlled by a number of factors such as orientation of the olefins in the interface of host materials, the density of ionic sites of the interface, and the looseness of the molecular packing of the guests. Mixed intercalation of different kinds of host olefins and ketone resulted in the formation of regioselective cycloadducts depending on the kinds of above mentioned ionic interface.
Synthetic utility of silacyclobutane as a C3 building block in the constitution of carbon skeletons is described. Topics are (1) lithium carbenoids induced ring enlargement of silacyclobutane into silacyclopentane, (2) nucleophile-induced ring enlargement of 1- (1-iodoalkyl) silacyclobutane and 1- (1, 2-epoxyalkyl) silacyclobutane into silacyclopentane, (3) triethylborane-induced radical cyclization of 1-allyloxy-2-halosilacyclopentane, (4) noncatalyzed stereoselective allylation of carbonyl compounds with allylsilacyclobutanes, and (5) preparation of 3-methylenesilacyclobutane and its use in organic synthesis.
Total synthesis of the novel trehalase inhibitor, trehazolin was accomplished, and its absolute structure was determined. On the basis of this synthetic study, several related compounds including its stereoisomers were synthesized to investigate the effects of their stereochemistry and framework on the enzyme inhibitory activities. Further studies were carried out for the syntheses and biological evaluation of the trehazolin derivatives, which were derived from its natural aminocyclitol and modified at the terminal amino group of trehalamine. They were designed as compounds exhibiting the inhibition toward the other glucosidases such as intestinal maltase and isomaltase, judging from the structural similarity between D-glucose and trehalamine.
Artificial ribofuranoside receptors represent the molecular design and the synthetic strategy for our multi-functional artificial receptors. The design of the polypyridine-macrocyclic ribofuranoside receptors was based on the multipoint hydrogen bond complementarity between the receptors and methyl β- (D) -ribofuranoside. The binding affinity of the receptors for the ribofuranoside in CDCl3 was very high (up to Ka = 5.2 × 103M-1), so that even native ribose was extracted by them into such nonpolar solvents. Selective extraction of ribose by the receptors was observed. The selectivity is governed by the OH direction and the whole size of the sugars as well as their shapes. Furthermore, fluorescence emission of the receptors was largely enhanced in the presence of methyl β- (D) -ribofuranoside or ribose.