Makoto Onaka

Organic Syntheses Using Aluminosilicates

Publisher Summary This chapter discusses the usage of organic synthesis. Surfaces of porous inorganic solids have long been employed as “reaction fields” in organic reactions to produce bulk chemicals. Organic syntheses on porous solids have also been recognized as a useful synthetic method to produce fine chemicals with various functional groups. In many cases, the presence of inorganic materials enabled better yields and higher selectivities under much milder reaction conditions as compared with conventional reaction systems conducted in homogeneous solutions. Making good use of porous solids, such as silica and alumina in liquid phase, organic reactions provides various advantages, such as inclusion of a reaction substrate and a reagent into a small pore with nanometer dimensions, in the case of a bimolecular reaction, brings the two molecules into proximity, thus lowering the activation entropy of the reaction. The chapter describes liquid–phase organic reactions carried out below 100°C on zeolite and clay, comparing them with reactions carried out by existent synthetic methods from the standpoint of synthetic organic chemistry.

Clay-mediated meso-tetraarylporphyrin synthesis

Abstract meso -Tetraalporphyrin syntheses from aromatic aldehydes and pyrrole in clay nanospaces were investigated. The clay-promoted porphyrin synthesis was also contrasted with the Lindsey BF 3 -catalyzed system.

Hydrosilylation of carbonyl compounds catalyzed by solid acids and bases

Abstract Hydrosilylation of carbonyl compounds with hydrosilane is efficiently catalyzed by inorganic solid acids and bases such as Fe 3+ ion-exchanged montmorillonite and hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ) at reaction temperatures between 25 and 90 °C. Enones are also selectively hydrosilylated in the presence of hydroxyapatite to afford the corresponding 1,2-addition products in high yields.

Acidity comparison between ion-exchanged clay montmorillonites by using silylation of alcohol

Abstract Acidities of various ion-exchanged clay montmorillonites in organic media are compared by use of the reaction of a primary alcohol with allyltrimethylsilane. The order of catalytic activities of the montmorillonites coincide with a sequence of hydration enthalpy of exchanged cations in the clays.

Novel catalytic action of clay montmorillonite on the addition reactions of silyl ketene acetals to α,β-acetylenic esters

Abstract Clay montmorillonite shows novel catalytic behavior to the addition of silyl ketene acetals to ynoates as a heterogeneous solid acid, and this activity has been compared with that obtained with trimethylsilyl triflate.

Clay Montmorillonite-catalyzed regioselective addition of silyl ketene acetals to pyridine derivatives: synthesis of N-silyldihydropyridines

Abstract Clay montmorillonite is an efficient catalyst for addition of silyl ketene acetals to pyridine derivatives with electron-withdrawing groups to afford N-silyldihydropyridines.

New application of solid base to regioselective ring openings of functionalized epoxides and oxetanes with cyanotrimethylsilane

Abstract Solid bases such as magnesium oxide, calcium oxide, and hydroxyapatite were successfully applied to the reactions of cyanotrimethylsilane with epoxides and oxetanes bearing alkyl substituents and diverse functional groups. The solid base-catalyzed systems were found to induce the ring openings of epoxides and oxetanes much more efficiently and regioselectively, as compared with the conventional, homogeneous acid-promoted systems. The high regioselection is ascribed to a nucleophilic ring opening of a cyanide ion through the coordination of cyanotrimethylsilane to base sites on solid bases.

Regioselective reductive opening of 2,3-epoxy alcohol derivatives with lithium borohydride in a solid state

Abstract 2,3-Epoxy alcohol derivatives were reduced regiospecifically with lithium borohydride in a solid state suspended in hexane to yield the corresponding C-3 opening products.

Iron-exchanged Montmorillonite as an Efficient Acid Catalyst in Liquid-Phase Organic Synthesis

Fe 3+ exchanged montmorillonite acted as a solid acid catalyst activating carbonyl groups much more efficiently than a homogeneous superacid of trifluoromethanesulfonic acid and its silyl ester in liquid-phase carbon-carbon bond-forming reactions using enol silanes and silyl cyanide as the nucleophiles to be added to carbonyl compounds. The trialkylsilyl cations formed on the surface of clay silicate layers appear to be responsible for enhancing the reactions as highly active Lewis acid sites.

Selective N-Monoalkylation of aniline derivatives by use of alkali cation exchanged X- and Y-type zeolites

Alkali cation exchanged X- and Y-type zeolites are employed to promote the reactions of aniline derivatives with alkylating agents in organic solvent. The N-alkylation is accelerated by the cooperative function of the acid and base sites on the potassium cation exchanged X- and Y-type zeolites to give the N-monoalkylated product in very high selectivity. Especially the use of the zeolite is found to be effective for N-alkylation of deactivated aromatic amines like nitroaniline. The highly selective N-monoalkylation is attributed to the reaction occurring inside the homogeneous narrow cavities of zeolites.