Investigation on 1,4‐dichlorophthalazine‐derivatized cinchona alkaloids‐catalyzed asymmetric “interrupted” Feist–Bénary reaction

Abstract

Different 1,4-dichlorophthalazine-cinchona alkaloid derivatives have been used to catalyze the asymmetric "interrupted" Feist-Bénary reaction of ethyl bromopyruvate/substituted bromoketoesters and beta-dicarbonyl compounds. The corresponding hydroxydihydrofurans have been obtained in excellent yields and with up to 91%ee.

Cinchona Alkaloid-Silyl Ether Derivatives as Organocatalysts for Asymmetric “Interrupted” Feist-Bénary Reaction

“…As expected, the opposite enantiomer as the major product was obtained, but with a low ee value (55%ee, entry 6). The configuration of all the products were confirmed through comparison of the optical rotation with a value from the literature [6]. a Unless noted, reactions were carried out using 5 mol% of catalyst at -78˚C.…”

“…The reaction mixture was then concentrated and purified by flash chromatography on silica gel (CH 2 Cl 2 /MeOH, 100/1). The structure of product 6c and 6d were determined by NMR analysis and proved to be correct according to the data from literature [6].…”

“…Interestingly, slight changes to a substituent of the catalysts or different cinchona alkaloids significantly affected the enantiomeric purity of products (14-98%). In our previous study, we reported the investigation of 1,4-dichlorophthalazine [6] and 3,6-dichloropyridazine-cinchona alkaloid derivatives [7] in asymmetric IFB reaction. Here we reported a series of new cinchona alkaloid-silyl ether derivatives and the application in asymmetric IFB reaction(Fig.…”

Estudos envolvendo a adição nucleofílica de 1,3-ciclohexanodionas a 1,4-diaril-1,3-diinos

“…Sua generalidade quanto a natureza do substrato foi estudada -utilização de βcetoésteres, β-oxopropionatos, β-dicetonas e β-dialdeídos 22 -, como também a influência da variação das condições reacionais e da natureza do catalisador 23,24 . Sua versão enantiosseletiva 25 , modificações 26,27,28 sobre a reação e aplicações em síntese também foram relatadas 21,29,30,31,32,33 Esquema 5.…”