Hirotaka Kagoshima

BRONSTED ACID-CATALYZED AZA DIELS-ALDER REACTION OF DANISHEFSKY'S DIENE WITH ALDIMINE GENERATED IN SITU FROM ALDEHYDE AND AMINE IN AQUEOUS MEDIA

Abstract Three-component aza Diels-Alder reaction, starting from aldehyde, aniline, and Danishefskys diene, took place smoothly under the influence of HBF 4 in aqueous media to afford dihydro-4-pyridone derivatives in high yields.

Brønsted Acid-Catalyzed Mannich-Type Reactions in Aqueous Media

HBF4-catalyzed Mannich-type reaction of silyl enolates with aldimines took place smoothly in aqueous organic solvent to afford β-aminocarbonyl compounds in high yields. The HBF4-catalyzed Mannich-type reaction also proceeded smoothly in water without organic solvent in the presence of a surfactant. A three-component synthesis starting from aldehyde, amine, and silyl enolate was successfully realized by means of a Bronsted acid in aqueous media.

A highly stereo-divergent Mannich-type reaction catalyzed by Brønsted acid in aqueous media

Abstract anti And syn stereoselectivity on the HBF4-catalyzed Mannich-type reaction of ketene silyl acetal derived from α-oxy esters with aldimines were investigated. Whereas use of ketene silyl acetal derived from aryl ester in aqueous 2-propanol gave anti β-amino-α-siloxy ester with excellent stereoselectivity, use of ketene silyl acetal derived from methyl ester in water in the presence of sodium dodecyl sulfate gave the syn isomer preferentially.

Lewis acid-mediated [3+2] cycloaddition of allyltriisopropylsilane to N-sulfonyl aldimines

Abstract BF3·OEt2-mediated [3+2] cycloaddition of allyltriisopropylsilane to N-sulfonyl aldimine afforded silyl substituted pyrrolidines in good yields. Excellent cis selectivity was observed with aromatic aldimines.

CHIRAL SYNTHESES OF 2,3,5-TRISUBSTITUTED PYRROLIDINES BY SILICON-DIRECTED CYCLIZATION OF ALLYLSILANES BEARING A SULFONAMIDE MOIETY

Abstract Bronsted acid-catalyzed cyclization of chiral N-tosyl-3-silyl-4-pentenamine proceeded smoothly by way of a β-silyl carbocation intermediate to furnish 2,3,5-trisubstituted pyrrolidines in enantiomerically pure form.

Chemoselective allylation of aldimine with allyltriethylgermane by the combined use of BF3•OEt2 and AcOH

Allyltriethylgermane reacts with aldimines in preference to aldehydes by means of BF3•OEt2 and AcOH to afford homoallylic amines in high yields; three component syntheses of homoallytic amines starting from aldehyde, aniline and allylgermane were successfully achieved.