Yoichi M. A. Yamada

Asymmetric Suzuki–Miyaura Coupling in Water with a Chiral Palladium Catalyst Supported on an Amphiphilic Resin

You oughta use water: Broad functional-group (FG) tolerance was observed for the title coupling of aryl halides (X = Cl, Br, I) and aryl boronic acids to give biaryl compounds with up to 94% ee. The chiral imidazoindole phosphine-palladium catalyst supported on an amphiphilic polystyrene-poly(ethylene glycol) (PS-PEG) resin could be recycled readily.

Self-assembled poly(imidazole-palladium): highly active, reusable catalyst at parts per million to parts per billion levels.

Metalloenzymes are essential proteins with vital activity that promote high-efficiency enzymatic reactions. To ensure catalytic activity, stability, and reusability for safe, nontoxic, sustainable chemistry, and green organic synthesis, it is important to develop metalloenzyme-inspired polymer-supported metal catalysts. Here, we present a highly active, reusable, self-assembled catalyst of poly(imidazole-acrylamide) and palladium species inspired by metalloenzymes and apply our convolution methodology to the preparation of polymeric metal catalysts. Thus, a metalloenzyme-inspired polymeric imidazole Pd catalyst (MEPI-Pd) was readily prepared by the coordinative convolution of (NH(4))(2)PdCl(4) and poly[(N-vinylimidazole)-co-(N-isopropylacrylamide)(5)] in a methanol-water solution at 80 °C for 30 min. SEM observation revealed that MEPI-Pd has a globular-aggregated, self-assembled structure. TEM observation and XPS and EDX analyses indicated that PdCl(2) and Pd(0) nanoparticles were uniformly dispersed in MEPI-Pd. MEPI-Pd was utilized for the allylic arylation/alkenylation/vinylation of allylic esters and carbonates with aryl/alkenylboronic acids, vinylboronic acid esters, and tetraaryl borates. Even 0.8-40 mol ppm Pd of MEPI-Pd efficiently promoted allylic arylation/alkenylation/vinylation in alcohol and/or water with a catalytic turnover number (TON) of 20,000-1,250,000. Furthermore, MEPI-Pd efficiently promoted the Suzuki-Miyaura reaction of a variety of inactivated aryl chlorides as well as aryl bromides and iodides in water with a TON of up to 3,570,000. MEPI-Pd was reused for the allylic arylation and Suzuki-Miyaura reaction of an aryl chloride without loss of catalytic activity.

Efficient Baylis–Hillman reactions promoted by mild cooperative catalysts and their application to catalytic asymmetric synthesis

Abstract Baylis–Hillman reactions were promoted by mild cooperative catalysts of tributylphosphine with phenols such as (±)-1,1′-bi-2-naphthol (BINOL) in THF to give α-methylene-β-hydroxyalkanones in high yield. The reactions proceeded much faster in the presence of 1,1′-bi-2-naphthol than in its absence. The 1H NMR studies suggested that 1,1′-bi-2-naphthol functions as a Bronsted acid to activate the carbonyl group of an aldehyde and a polarized alkene. Application of the reactions to catalytic asymmetric synthesis was examined by using cooperative catalysts of tributylphosphine with the calcium chiral catalyst to give the desired product with fairly good % ee in fairly good yield.

Amphiphilic Self-Assembled Polymeric Copper Catalyst to Parts per Million Levels: Click Chemistry

Self-assembly of copper sulfate and a poly(imidazole-acrylamide) amphiphile provided a highly active, reusable, globular, solid-phase catalyst for click chemistry. The self-assembled polymeric Cu catalyst was readily prepared from poly(N-isopropylacrylamide-co-N-vinylimidazole) and CuSO(4) via coordinative convolution. The surface of the catalyst was covered with globular particles tens of nanometers in diameter, and those sheetlike composites were layered to build an aggregated structure. Moreover, the imidazole units in the polymeric ligand coordinate to CuSO(4) to give a self-assembled, layered, polymeric copper complex. The insoluble amphiphilic polymeric imidazole Cu catalyst with even 4.5-45 mol ppm drove the Huisgen 1,3-dipolar cycloaddition of a variety of alkynes and organic azides, including the three-component cyclization of a variety of alkynes, organic halides, and sodium azide. The catalytic turnover number and frequency were up to 209000 and 6740 h(-1), respectively. The catalyst was readily reused without loss of catalytic activity to give the corresponding triazoles quantitatively.

A Palladium‐Nanoparticle and Silicon‐Nanowire‐Array Hybrid: A Platform for Catalytic Heterogeneous Reactions

We report the development of a silicon nanowire array-stabilized palladium nanoparticle catalyst, SiNA-Pd. Its use in the palladium-catalyzed Mizoroki-Heck reaction, the hydrogenation of an alkene, the hydrogenolysis of nitrobenzene, the hydrosilylation of an α,β-unsaturated ketone, and the C-H bond functionalization reactions of thiophenes and indoles achieved a quantitative production with high reusability. The catalytic activity reached several hundred-mol ppb of palladium, reaching a TON of 2 000 000.

A Highly Active and Reusable Self‐Assembled Poly(Imidazole/Palladium) Catalyst: Allylic Arylation/Alkenylation

Metalloproteins, supramolecular composites of polymeric peptides and metal species, are essential organic transformation systems for maintaining vital activity to promote highly efficient enzymatic reactions. For example, the metalloprotein catalase provides extremely high turnover efficiencies of 40000 000 sec . However, metalloproteins are easily disassimilated and exhibit substrate specificity. Therefore, the development of a metalloprotein-inspired polymeric metal catalyst is an important objective for organic, organometallic, and supramolecular chemistry, as well as sustainable and industrial process chemistry. These catalysts are expected to provide highly active and selective organic transformation systems with high reusability, safety, cleanness, ease of use, and substrate tolerance. In metalloproteins, the basic imidazole unit within histidine plays an important role for binding with metal species, thus forming catalytic sites within a supramolecular structure; therefore imidazole ligands are widely utilized as the building blocks of artificial metal– organic self-assembled supramolecules for functional materials including catalysts. We believe that some insoluble selfassembled complexes of amphiphilic polymeric imidazoles and metal species could offer catalytic activities as high as that of metalloproteins, but with much greater reusability. We recently reported the preparation of highly active, reusable, heterogeneous polymeric metal catalysts for organic transformations, also known as molecular convolution, where a soluble linear polymer having multiple ligand groups is convoluted (noncovalently cross-linked) with transition metals through coordinative or ionic complexation. We envisioned applying this concept to the preparation of metalloprotein-inspired polymeric imidazole metal catalysts to produce highly active, reusable, heterogeneous, selfassembled catalysts. Herein we report the development of a novel polymeric imidazole/acrylamide palladium catalyst that was utilized for the allylic arylation/alkenylation of allylic esters with aryl/alkenylboronic acids and tetraaryl borates. Even 0.8–40 ppm of the catalyst efficiently promoted the allylic arylation/alkenylation in alcohol or water with a catalytic turnover number (TON) of 20 000–1250 000, and the catalyst was reusable without loss of catalytic activity. We found that our molecular convolution methodology provided the globular-aggregated, self-assembled structure of the catalyst. The metalloprotein-inspired polymeric imidazole/palladium catalyst 3 (MPPI-Pd) was readily prepared as follows. When the coordinative convolution of [(NH4)2PdCl4] (2 ; 1 mol equiv Pd) and poly[(N-vinylimidazole)-co-(N-isopropylacrylamide)5] [5] (1; 2 molequiv imidazole) was carried out in a methanol/water (1:1) solution at 80 8C for 30 minutes, the resulting compound 3 (brown powder) was precipitated out (Scheme 1). The precipitates were hardly soluble in water, methanol, DMF, EtOAc, CH2Cl2, or n-hexane. As shown in the top left panel of Figure 1, scanning electron microscopy

Palladium Membrane‐Installed Microchannel Devices for Instantaneous Suzuki–Miyaura Cross‐Coupling

Instantaneous catalytic carbon-carbon bond-forming reactions were achieved in catalytic membrane-installed microchannel devices that have a polymeric palladium-complex membrane. The catalytic membrane-installed microchannel devices were provided inside the microchannels by means of coordinative and ionic molecular convolution at the interface between the organic and aqueous phases flowing laminarly, in which both non-crosslinked linear polymer ligands and palladium species dissolved. The palladium-catalyzed Suzuki-Miyaura reaction of aryl, heteroaryl, and alkenyl halides with arylboronic acids and sodium tetraarylborates was performed with the catalytic membrane-installed microchannel devices to give quantitative yields of biaryls, heterobiaryls, and aryl alkenes within 5 s of residence time in the defined channel region. These microchannel devices were applied to the instantaneous allylic arylation reaction of allylic esters with arylboron reagents under microflow conditions to afford the corresponding coupling products within 1 s of residence time.

Development of an amphiphilic resin-dispersion of nanopalladium and nanoplatinum catalysts: design, preparation, and their use in green organic transformations.

An amphiphilic polymer resin-dispersion of nanoparticles of palladium was designed and prepared with a view toward use for catalysis in water. The amphiphilic polystyrene-poly(ethylene glycol) (PS-PEG) resin-dispersion of nanoparticles of palladium exhibited high catalytic performance in the hydrodechlorination of chloroarenes under aqueous conditions. The amphiphilic resin-supported nanopalladium and nanoplatinum particles also catalyzed aerobic oxidation of various alcohols including nonactivated aliphatic and alicyclic alcohols, which is one of the most fundamental and important yet immature processes in organic chemistry, in water under an atmospheric pressure of oxygen gas to form aldehydes, ketones, and carboxylic acids to meet green chemical requirements. Viologen polymer-supported nanopalladium catalyst realized alpha-alkylation of ketones with primary alcohols as the alkylating agents.

Highly efficient iron(0) nanoparticle-catalyzed hydrogenation in water in flow

Highly efficient catalytic hydrogenations are achieved by using amphiphilic polymer-stabilized Fe(0) nanoparticle (Fe NP) catalysts in ethanol or water in a flow reactor. Alkenes, alkynes, aromatic imines and aldehydes were hydrogenated nearly quantitatively in most cases. Aliphatic amines and aldehydes, ketone, ester, arene, nitro, and aryl halide functionalities are not affected, which provides an interesting chemoselectivity. The Fe NPs used in this system are stabilized and protected by an amphiphilic polymer resin, providing a unique system that combines long-term stability and high activity. The NPs were characterized by TEM of microtomed resin, which established that iron remains in the zero-valent form despite exposure to water and oxygen. The amphiphilic resin-supported Fe(0) nanoparticles in water and in flow provide a novel, robust, cheap and environmentally benign catalyst system for chemoselective hydrogenations.

An efficient heterogeneous Heck reaction promoted by a new assembled catalyst of palladium and non-cross-linked amphiphilic polymer

Abstract A newly assembled insoluble catalyst 1b composed of palladium and non-cross-linked amphiphilic polymer was developed. It was named PdAS-V: a supramolecular complex of (NH 4 ) 2 Pd Cl 4 ( 2 ) and poly[( N -isopropylacrylamide) 5 - co -(4-diphenylstyrylphosphine)] ( 3b ). The use of 8.0×10 −7 –5.0×10 −5 mol equiv. of PdAS-V efficiently catalyzed the Heck reaction of aryl iodides with acrylates and styrenes. The turnover number of PdAS-V reached up to 1,150,000, and the catalyst was recycled five times without any decrease in its activity.