Sangjune Park

Synthesis of Pyrroles from Terminal Alkynes, N-Sulfonyl Azides, and Alkenyl Alkyl Ethers through 1-Sulfonyl-1,2,3-triazoles

A method for synthesis of substituted pyrroles has been developed. 1-Sulfonyl-1,2,3-triazoles generated from terminal alkynes gave α-imino rhodium carbene complexes, which when reacted with alkenyl alkyl ethers afforded substituted pyrroles. The method can be efficiently applied to a one-pot sequential reaction starting from terminal alkynes.

Rhodium-catalyzed oxidative coupling through C–H activation and annulation directed by phosphonamide and phosphinamide groups

Rhodium-catalyzed oxidative coupling reactions via C-H activation and annulation directed by phosphonamide and phosphinamide groups were developed under aerobic conditions, which produced benzazaphosphole 1-oxides and phosphaisoquinolin-1-oxides.

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.

Diastereoselective N-Sulfonylaminoalkenylation of Azulenes from Terminal Alkynes and Azides via N-Sulfonyl-1,2,3-triazoles

The development of rhodium-catalyzed diastereoselective N-sulfonylaminoalkenylation of azulenes using N-sulfonyltriazoles is described. This procedure can be successfully applied to rhodium-catalyzed diastereoselective N-sulfonylaminoalkenylation of azulenes starting from terminal alkynes and N-sulfonylazides via a three-component semi-one-pot process.

Rhodium-catalyzed oxidative C-H activation/cyclization for the synthesis of phosphaisocoumarins and phosphorous 2-pyrones.

Rhodium-catalyzed cyclization of phosphinic acids and phosphonic monoesters with alkynes has been developed. The oxidative annulation proceeds with complete conversion of phosphinic acid derivatives and allowed the atom-economic preparation of useful phosphaisocoumarins with high yield and selectivity. The reaction is tolerant of extensive substitution on the phosphinic acid, phosphonic monoester and alkyne, including halides, ketone, and hydroxyl groups as substituents. Furthermore, we found that alkenylphosphonic monoesters proceed to give a wide range of phosphorus 2-pyrones through oxidative annulation with alkynes. Mechanistic studies revealed that C-H bond metalation was the rate-limiting step.

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.

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 Azulen-1-yl Ketones via Oxidative Cleavage of C–C Multiple Bonds in N-Sulfonyl Enamides and 1-Alkynes under Air and Natural Sunlight

A synthetic method to prepare azulen-1-yl ketones was developed via oxidative cleavage of the C-C double bond in the reaction of easily obtainable N-sulfonyl enamides with Cs2CO3 under air and natural sunlight and in the absence of a photosensitizer. Oxidative cleavage of C-C triple bonds was also demonstrated for the synthesis of azulen-1-yl ketones via a tandem Cu-catalyzed [3 + 2] cycloaddition, Rh-catalyzed arylation, photooxygenation, and ring-opening reaction in one pot under air and natural sunlight.

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.