Continuous-flow synthesis of carboxylic acids from alcohols platinum and silicon dioxide-catalyzed hydrogen peroxide oxidation.

A continuous-flow method for the direct oxidation of alcohols to carboxylic acids is reported, employing hydrogen peroxide (HO) and a platinum (Pt) catalyst within a flow reactor system. This approach allows for precise control over the contact time between the reactants and the catalyst, enabling optimization of reaction conditions. By analyzing the yields of both aldehydes and carboxylic acids as a function of weight hourly space velocity (WHSV), selective synthesis of carboxylic acids was achieved without the formation of corresponding aldehydes.

Brønsted base-catalyzed imino-ene-type allylation reactions of simple alkenes as unactivated allyl compounds.

Catalytic imino-ene-type allylation reactions of unactivated allyl compounds were achieved. In the presence of a catalytic amount of a strongly basic KOBu-LiTMP or NaOBu-LiTMP mixed system, the desired reactions proceeded smoothly at low temperature. Notably, a gaseous alkene, propylene, could also be used in this reaction system.

Direct and quantitative monitoring of catalytic organic reactions under heterogeneous conditions using direct analysis in real time mass spectrometry.

This new method overcomes problems of conventional analytical methodologies such as light scattering and sampling reproducibility issues. We used this method for mechanistic studies of catalytic reactions under heterogeneous conditions. Direct-type hydroxymethylation reactions and Mukaiyama-type hydroxymethylation reactions both catalyzed by a scandium-bipyridine ligand complex under micellar conditions were employed as examples of heterogeneous reactions.

Chiral Lewis acids integrated with single-walled carbon nanotubes for asymmetric catalysis in water.

The development of highly reactive and stereoselective catalytic systems is required not only to improve existing synthetic methods but also to invent distinct chemical reactions. Herein, a homogenized combination of nickel-based Lewis acid-surfactant-combined catalysts and single-walled carbon nanotubes is shown to exhibit substantial activity in water. In addition to the enhanced reactivity, stereoselective performance and long-term stability were demonstrated in asymmetric conjugate addition reactions of aldoximes to furnish chiral nitrones in high yields with excellent selectivities.

Development of a Simple Adjustable Zinc Acid/Base Hybrid Catalyst for C-C and C-O Bond-Forming and C-C Bond-Cleavage Reactions.

A newly designed zinc Lewis acid/base hybrid catalyst was developed. By adjusting the Lewis acidity of the zinc center, aldol-type additions of 2-picolylamine Schiff base to aldehydes proceeded smoothly to afford syn-aldol adduct equivalents, trans-N,O-acetal adducts, in high yields with high selectivities. NMR experiments, including microchanneled cell for synthesis monitoring (MICCS) NMR analysis, revealed that anti-aldol adducts were formed at the initial stage of the reactions under kinetic control, but the final products were the trans-(syn)-N,O-acetal adducts that were produced through a retro-aldol process under thermodynamic control.

Chiral Nanoparticles/Lewis Acids as Cooperative Catalysts for Asymmetric 1,4-Addition of Arylboronic Acids to α,β-Unsaturated Amides.

Cooperative catalysts consisting of chiral Rh/Ag nanoparticles and Sc(OTf)3 have been developed that catalyze asymmetric 1,4-addition reactions of arylboronic acids with α,β-unsaturated amides efficiently. The reaction has been considered one of the most challenging reactions because of the low reactivity of the amide substrates. The new catalysts provide the desired products with outstanding enantioselectivities (>98 % ee) in the presence of low loadings (<0.

Flow "Fine" Synthesis: High Yielding and Selective Organic Synthesis by Flow Methods.

The concept of flow "fine" synthesis, that is, high yielding and selective organic synthesis by flow methods, is described. Some examples of flow "fine" synthesis of natural products and APIs are discussed. Flow methods have several advantages over batch methods in terms of environmental compatibility, efficiency, and safety.

Self-Assembled Nanocomposite Organic Polymers with Aluminum and Scandium as Heterogeneous Water-Compatible Lewis Acid Catalysts.

While water-compatible Lewis acids have great potential as accessible and environmentally benign catalysts for various organic transformations, efficient immobilization of such Lewis acids while keeping high activity and without leaching of metals even under aqueous conditions is a challenging task. Self-assembled nanocomposite catalysts of organic polymers, carbon black, aluminum reductants, and scandium salts as heterogeneous water-compatible Lewis acid catalysts are described. These catalysts could be successfully applied to various C-C bond-forming reactions without leaching of metals.

Size of gold nanoparticles driving selective amide synthesis through aerobic condensation of aldehydes and amines.

Metal nanoparticles (NPs) have attracted much attention in many fields due to their intrinsic characteristics. It is generally accepted that smaller NPs (1.5-3 nm) are more active than larger NPs, and reverse cases are very rare.

Visible-light-mediated chan-lam coupling reactions of aryl boronic acids and aniline derivatives.

The copper(II)-catalyzed aerobic oxidative coupling reaction between aryl boronic acids and aniline derivatives was found to be improved significantly under visible-light-mediated photoredox catalysis. The substrate scope of this oxidative Chan-Lam reaction was thus expanded to include electron-deficient aryl boronic acids as viable starting materials.

Catalytic imine-imine cross-coupling reactions.

We report here efficient catalytic imine-imine cross-coupling reactions based on an umpolung strategy; an imine bearing a 9-fluorenyl moiety on its nitrogen atom, which acted as a nucleophile, reacted with another imine to afford an imine-imine cross-coupling adduct in high yield. Furthermore, a chiral guanidine acted as a chiral catalyst for these coupling reactions, and optically active 1,2-diamines were obtained in high yields with high enantioselectivities.

A cooperative water effect in proazaphosphatrane-catalysed heterocycle synthesis.

The synthesis of oxazolines and imidazolines was achieved by activation of isocyanides with water. Mechanistic studies show that the organosuperbase proazaphosphatrane is tolerant of water within the reaction medium, with a beneficial and cooperative effect being observed.

Chiral metal nanoparticle-catalyzed asymmetric C-C bond formation reactions.

Chiral ligand-modified metal nanoparticles possess an attractive potential for application in asymmetric synthesis. This article focuses on chiral-nanoparticle-catalyzed asymmetric C-C bond formation reactions and discusses the nature of the active species.

A heterogeneous layered bifunctional catalyst for the integration of aerobic oxidation and asymmetric C-C bond formation.

The design and synthesis of a heterogeneous bifunctional chiral catalyst for the sequential aerobic oxidation-asymmetric Michael reactions between primary allylic alcohols and dibenzyl malonate are described. Interestingly, we found that layering bimetallic nanoparticles over the organocatalyst, within the chiral composite material, is crucial for catalytic activity.

Allylation reactions of aldehydes with allylboronates in aqueous media: unique reactivity and selectivity that are only observed in the presence of water.

Zn(OH)2-catalyzed allylation reactions of aldehydes with allylboronates in aqueous media have been developed. In contrast to conventional allylboration reactions of aldehydes in organic solvents, the α-addition products were obtained exclusively. A catalytic cycle in which the allylzinc species was generated through a B-to-Zn exchange process is proposed and kinetic studies were performed.

Catalytic silicon-mediated carbon-carbon bond-forming reactions of unactivated amides.

In the presence of catalytic amounts of trialkylsilyl triflate and triethylamine, unactivated amides react with imines to afford the corresponding Mannich-type adducts in high yields with high anti selectivities. While silicon enolates have been widely used in organic synthesis for four decades, this is the first example of the catalytic use of the silicon species, to the best of our knowledge. Moreover, it is noteworthy that unactivated simple amides bearing α-protons that are less acidic than those of ketones and aldehydes can be successfully used in catalytic direct-type addition reactions.

Alkaline earth metal catalysts for asymmetric reactions.

The group 2 alkaline earth metals calcium (Ca), strontium (Sr), and barium (Ba) are among the most common elements on Earth, abundant in both the sea and the Earth's crust. Although they are familiar in our daily lives, their application to organic synthesis has, so far, been limited. Some particularly useful properties of these elements include (i) low electronegativity, (ii) a stable oxidation state of +2, meaning that they can potentially form two covalent bonds with anions, and (iii) the ability to occupy a variety of coordination sites due to their large ionic radius.

Polymer-incarcerated metal(0) cluster catalysts.

Polymer-incarcerated metal(0) nanocluster catalysts were developed based on two techniques: microencapsulation and cross-linking. Pd, Au, Pt, and bimetallic nanoclusters could be efficiently immobilized on polymers containing benzene rings keeping subnanometer- to nanometer-size clusters. Catalysts could be used for redox reactions using molecular hydrogen and oxygen, and could be reused without aggregation of nanoclusters and leaching of metals.

Aldehyde allylation with allylboronates providing alpha-addition products.

Zn(OH)(2)-catalyzed allylation reactions of allylboronates with aldehydes proceeded smoothly in aqueous media; when alpha-substituted allylboronates were employed, the alpha-addition products were obtained exclusively, and syn-adducts were formed selectively in most cases; the use of Zn(OH)(2) with dmp (ligand) in aqueous media is the key to these reactions.

Catalytic carbanion reactions: formation and reaction of carbanions from ester or amide equivalents using catalytic amounts of bases.

We describe here carbanion reactions using catalytic amounts of bases. The carbanions formed are different from conventional carbanions in which stoichiometric amounts of bases are needed for the formation. Two types of reactions using such carbanions from amide (imido) and ester equivalents are discussed.

Calcium-catalyzed diastereo- and enantioselective 1,4-addition of glycine derivatives to alpha,beta-unsaturated esters.

The first highly diastereo- and enantioselective catalytic asymmetric 1,4-addition reactions of a glycine Schiff base to beta-substituted alpha,beta-unsaturated esters have been developed. The reaction pathway was successfully controlled, and the desired 1,4-addition products were exclusively obtained with high enantioselectivities. The product obtained was converted to a 3-substituted glutamic acid derivative by acid hydrolysis.