Practical Asymmetric Synthesis of Chiral Sulfoximines via Sulfur-Selective Alkylation.

Chiral sulfoximines have recently been considered as promising bioisosteres in medicinal chemistry. However, methods for preparing chiral sulfoximines in a stereoselective manner are underdeveloped. Herein, we demonstrate an asymmetric synthesis of chiral sulfoximines through a stereospecific -alkylation of readily accessible chiral sulfinamides under practical conditions.

Low-oxidation state indium-catalyzed C-C bond formation.

The development of innovative metal catalysis for selective bond formation is an important task in organic chemistry. The group 13 metal indium is appealing for catalysis because indium-based reagents are minimally toxic, selective, and tolerant toward various functional groups. Among elements in this group, the most stable oxidation state is typically +3, but in molecules with larger group 13 atoms, the chemistry of the +1 oxidation state is also important.

Continuous flow hydrogenation using polysilane-supported palladium/alumina hybrid catalysts.

Continuous flow systems for hydrogenation using polysilane-supported palladium/alumina (Pd/(PSi-Al(2)O(3))) hybrid catalysts were developed. Our original Pd/(PSi-Al(2)O(3)) catalysts were used successfully in these systems and the hydrogenation of unsaturated C-C bonds and a nitro group, deprotection of a carbobenzyloxy (Cbz) group, and a dehalogenation reaction proceeded smoothly. The catalyst retained high activity for at least 8 h under neat conditions.

Chiral Sc-catalyzed asymmetric Michael reactions of thiols with enones in water.

Asymmetric Michael reactions of thiols with enones were catalyzed by a Sc(OTf)(3)-chiral bipyridine complex at room temperature in water without using any organic solvents, to afford the desired sulfides in high yields with high enantioselectivities.

Polymer-incarcerated gold-palladium nanoclusters with boron on carbon: a mild and efficient catalyst for the sequential aerobic oxidation-Michael addition of 1,3-dicarbonyl compounds to allylic alcohols.

We have developed a polymer-incarcerated bimetallic Au-Pd nanocluster and boron as a catalyst for the sequential oxidation-addition reaction of 1,3-dicarbonyl compounds with allylic alcohols. The desired tandem reaction products were obtained in good to excellent yields under mild conditions with broad substrate scope. In the course of our studies, we discovered that the excess reducing agent, sodium borohydride, reacts with the polymer backbone to generate an immobilized tetravalent boron catalyst for the Michael reaction.

Indium(I)-catalyzed alkyl-allyl coupling between ethers and an allylborane.

An efficient method for alkyl-allyl cross-coupling between ethers and a 9-BBN-derived allylborane catalyzed by indium(I) triflate has been developed. The allylborane proved to be essential to obtain the desired products in high yields. The reaction displayed good substrate scope including high functional group tolerance.

Direct use of allylic alcohols in the allylation of sulfonylimidates.

We have developed catalytic allylation reactions of sulfonylimidates using allylic alcohols as allylating reagents. Stoichiometric amounts of neither activators nor bases are required in this reaction.

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.

In situ coupled oxidation cycle catalyzed by highly active and reusable Pt-catalysts: dehydrogenative oxidation reactions in the presence of a catalytic amount of o-chloranil using molecular oxygen as the terminal oxidant.

An in situ coupled oxidation cycle that allows catalytic oxidation of a substrate with catalytic amounts of o-chloranil and novel reusable polymer-immobilized platinum nanocluster catalysts using molecular oxygen as the terminal oxidant was developed.

Catalytic asymmetric protonation of chiral calcium enolates via 1,4-addition of malonates.

Catalytic asymmetric protonation of chiral calcium enolates was performed. Chiral calcium enolates, prepared in situ from imides and malonates via 1,4-addition in the presence of catalytic amounts of Ca(OEt)(2), Ph-PyBox, and achiral phenol, were smoothly protonated to afford adducts bearing tertiary asymmetric carbons in high yields with high enantioselectivities. The adducts were readily converted to optically active 2-substituted 1,5-dicarboxylic acid derivatives.

Unusual carbon-carbon bond formations between allylboronates and acetals or ketals catalyzed by a peculiar indium(I) Lewis acid.

In(I)OTf has been uncovered as an effective Lewis acid catalyst for unprecedented nucleophilic substitution of acetals or ketals with allylboronates. A transmetalative S(N)1 mechanism is proposed in which a single In(I) center acts as a dual catalyst to activate both reagents sequentially. Contrary to the classic gamma-selectivity of allylsilanes (Hosomi-Sakurai reaction), this In(I)-catalyzed borono variant displays distinct alpha-selectivity.

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.

Asymmetric mannich reaction of malonates with imines catalyzed by a chiral calcium complex.

A chiral calcium complex was found to be effective for the Mannich reactions of malonates with N-Boc imines. The desired adducts were obtained in excellent yields (up to 95%) with moderate to good enantioselectivities (up to 77% ee).

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.

A gold-immobilized microchannel flow reactor for oxidation of alcohols with molecular oxygen.

Golden capillaries: A gold-immobilized capillary column reactor allows oxidation of alcohols to carbonyl compounds using molecular oxygen. These capillary columns (see picture) can be used for at least four days without loss of activity.

Catalytic direct-type substitution reaction of alpha-alkyl enolates: a Pd/Brønsted base-catalysed approach to the decarboxylative allylation of sulfonylimidates.

A mild and efficient process for the direct-type catalytic allylation of sulfonylimidates has been developed; this reaction represents the first example of Brønsted base-catalysed, in situ generation and use of alpha-alkyl enolates in substitution reactions; the success of this methodology stems from the tunable alpha-proton acidity and nucleophilicity of sulfonylimidates, which could be harnessed in the realization of a broader range of catalytic direct-type reactions using ester equivalents as nucleophiles.

Catalytic use of indium(0) for carbon-carbon bond transformations in water: general catalytic allylations of ketones with allylboronates.

We have discovered the unprecedented catalytic use of In(0) for catalytic C-C bond transformations. Remarkably, these general catalytic allylations of ketones proceeded smoothly in water as a sole solvent under mild conditions, and water proved to be essential for these reactions. Both the displayed substrate scope and the functional group tolerance were excellent.

Gold-platinum bimetallic clusters for aerobic oxidation of alcohols under ambient conditions.

We have developed gold/platinum alloyed bimetallic cluster catalysts supported on a cross-linked polystyrene derivative, which present much higher activity and selectivity than single metal gold or platinum clusters for aerobic oxidation of alcohols under ambient conditions.

Indium(i) iodide-catalyzed regio- and diastereoselective formal alpha-addition of an alpha-methylallylboronate to N-acylhydrazones.

Indium(i) iodide was found to catalyze the formal alpha-addition of an alpha-methylallylboronate to various N-acylhydrazones, in the presence of an alcohol additive, to afford the corresponding anti-alpha-adducts with high regio- and diastereoselectivity in high yields.