Taekyu Ryu

Synthesis of Phosphaisocoumarins through Rhodium-Catalyzed Cyclization Using Alkynes and Arylphosphonic Acid Monoesters

A rhodium-catalyzed cyclization using alkynes and arylphosphonic acid monoesters for the synthesis of phosphaisocoumarins is reported. A number of arylphosphonic acid monoesters were selectively cyclized in high yields with functional group tolerance. In addition, unsymmetrical alkynes are applied in high regioselectivity.

Synthesis of 2-aryl-2H-benzotrizoles from azobenzenes and N-sulfonyl azides through sequential rhodium-catalyzed amidation and oxidation in one pot.

An efficient synthetic method of 2-aryl-2H-benzotriazoles from nonprefunctionalized azobenzenes and N-sulfonyl azides via sequential Rh-catalyzed amidation (C-N bond formation) and oxidation (N-N bond formation) with PhI(OAc)2 in one pot is reported.

Rhodium-Catalyzed Oxidative Cyclization of Arylphosphonic Acid Monoethyl Esters with Alkenes: Efficient Synthesis of Benzoxaphosphole 1-Oxides

Rhodium-catalyzed tandem oxidative alkenylation and an intramolecular oxy-Michael reaction were developed using arylphosphonic acid monoethyl esters and alkenes under aerobic conditions, which produced benzoxaphosphole 1-oxides in good to excellent yields.

Synthesis of Pyrazines from Rhodium-Catalyzed Reaction of 2H-Azirines with N-Sulfonyl 1,2,3-Triazoles

An efficient synthetic route to a wide range of trisubstituted pyrazines is developed from Rh-catalyzed reaction of 2H-azirines with N-sulfonyl-1,2,3-triazoles through the elimination of nitrogen molecule and arylsulfinic acid. The present reaction proceeds through formation of in situ generated dihydropyrazines.

Synthesis of indenes via Brønsted acid catalyzed cyclization of diaryl- and alkyl aryl-1,3-dienes.

Substituted indenes can be synthesized via the Brønsted acid catalyzed cyclization of diaryl- and alkyl aryl-1,3-dienes. In this approach, treatment of symmetric or unsymmetric diaryl- and alkyl aryl-1,3-dienes with a catalytic amount of trifluoromethanesulfonic acid gives a variety of indene derivatives in good to excellent yields under mild conditions.

Synthesis of 2-Bromoimidazoles from Alkynes, N-Sulfonylazides, and Bromocyanides

A synthetic method for 2-bromoimidazoles is developed from Rh-catalyzed cyclization of N-sulfonyl-1,2,3-triazoles with bromocyanides. Cu-catalyzed [3 + 2] cycloaddition followed by Rh-catalyzed cyclization starting from alkynes, N-sulfonylazides, and bromocyanides is also demonstrated for de novo synthesis of 2-bromoimidazoles in one pot. Moreover, this work was successfully employed to introduce diverse functional groups to the 2-position of imidazoles via cross-coupling reaction.

Oxidative ortho-alkenylation of arylphosphine oxides by rhodium-catalyzed C–H bond twofold cleavage

An efficient Rh-catalyed oxidative ortho-alkenylation is reported from the reaction of arylphosphine oxides with activated and non-activated alkenes as well. The developed method is characterized by high selectivity, a wide substrate scope, and an excellent functional group tolerance.

Indium Tri(isopropoxide)-Catalyzed Selective Meerwein–Ponndorf–Verley Reduction of Aliphatic and Aromatic Aldehydes

Indium tri(isopropoxide)-catalyzed Meerwein-Ponndorf-Verley reduction of aliphatic and aromatic aldehydes in 2-propanol gave selectively the corresponding primary alcohols in good to excellent yields at room temperature. A wide range of functional groups including alkene, ether, ketone, ester, nitrile, and nitro were tolerated under the optimum reaction conditions. Chemoselective reductions were also achieved not only between aromatic aldehyde, aromatic ketone, and epoxide but also between aliphatic aldehyde and alkene.

Synthesis of N-Imidoyl and N-Oxoimidoyl Sulfoximines from 1-Alkynes, N-Sulfonyl Azides, and Sulfoximines

N-Imidoylation of sulfoximines is developed from a Cu-catalyzed three-component reaction from 1-alkynes, N-sulfonyl azides, and sulfoximines in THF at room temperature under air. In addition, N-oxoimidoylation of sulfoximines is accessed from a Cu-catalyzed three-component reaction from 1-alkynes, N-sulfonyl azides, and sulfoximines in THF at room temperature followed by a Cu-catalyzed oxidative reaction at 50 °C under air, producing N-oxoimidoyl sulfoximines.

Gold-catalyzed hydrosilyloxylation driving tandem aldol and Mannich reactions.

The chemoselective formation of an enolate from alkyne in the presence of a carbonyl and imine group was realized, which constructed a variety of structural motifs under exceedingly mild reaction conditions in a tandem process. Reaction driving tandem hydrosilyloxylation/aldol reactions was achieved through the formation of enol silyl ethers catalytically generated in situ from readily available alkynes. These reactions were expanded to obtain β-amino enol silyl ethers in good yields via the tandem hydrosilyloxylation/isomerization/Mannich reaction.