Organocatalyzed enantioselective aldol reaction of 1H-pyrrole-2,3-diones

Abstract

The enantioselective cross aldol reaction of 1-benzyl 4,5-dioxo-2-aryl-4,5-dihydro-1H-pyrrole-3-carboxylates and ketones was studied with proline derivatives or cinchona alkaloid-derived primary amines as the catalysts for the first time. trans-4-Benzoyloxy-L-proline (15) was found to be the best catalyst for acyclic ketones. For cyclohexanone, the best results were achieved with 9-deoxy-9-epi-aminoquinine (18) as the catalyst in the presence of racemic 1,1'-binaphthyl-2,2'-diyl hydrogen phosphate (19) as the cocatalyst. Using these protocols, 3-alkyl-3-hydroxy-1H-pyrrol-2(3H)-one derivatives were obtained in excellent yields and good to high ee values (up to 94% ee).

Organocatalytic asymmetric Henry reaction of 1H-pyrrole-2,3-diones with bifunctional amine-thiourea catalysts bearing multiple hydrogen-bond donors

“…A survey of the literature reveals that the study of 1 H -pyrrole-2,3-diones is mainly focused on three-component spiro-heterocyclization reactions [30–32]. However, for the catalytic asymmetric transformation, only one example of an aldol reaction of 1 H -pyrrole-2,3-diones with ketones has been reported so far (Scheme 1) [33]. Recently, our group developed a chiral bifunctional multiple hydrogen-bond amine-thiourea-catalyzed Michael reaction of acetyl phosphonates with nitroolefins, giving a series of β-substituted nitro compounds with excellent stereoselectivity [34].…”

Tricomponent spiro heterocyclization of pyrrolediones under the action of 4-hydroxycoumarin

“…The formation of compounds 2а and 2b occurs apparently through initial condensation of the keto carbonyl group in the position 3 of pyrrolediones 1а and 1b with the methylene group of diketo form of 4hydroxycoumarin (analogously to the condensation of these pyrrolediones with methylene-active compounds [3]) followed by the nucleophilic addition of the β-CH of the enol fragment of the second 4-hydroxycoumarin molecule to the carbon atom in the position 3 of the …”