Diastereoselective Construction of Cyclopropane-Fused Tetrahydroquinolines via a Sequential [4 + 2]/[2 + 1] Annulation Reaction
A sequential [4 + 2]/[2 + 1] annulation of α-aryl vinylsulfoniums with 2-aminochalcones and 2-(2-aminobenzylidene)-1H-indene-1,3(2H)-dione is reported that affords a series of cyclopropane-fused tetrahydroquinolines. The salient features of this novel and practical transformation include high efficiency, transition-metal-free nature, operational simplicity, and outstanding functional group tolerance.
Asymmetric Ring Opening/Cyclization/Retro-Mannich Reaction of Cyclopropyl Ketones with Aryl 1,2-Diamines for the Synthesis of Benzimidazole Derivatives
A highly efficient asymmetric ring-opening/cyclization/retro-Mannich reaction of cyclopropyl ketones with aryl 1,2-diamines has been realized using a chiral N,N′-dioxide/ScIIIcatalyst. Benzimidazoles containing chiral side chains were generated under mild reaction conditions in excellent outcomes (up to 99 % yield and 97 % ee). This method also provides efficient access to chiral benzimidazole-substituted amide and cycloheptene derivatives.
Asymmetric synthesis of 2,3-dihydropyrroles by ring-opening/ cyclization of cyclopropyl ketones using primary amines
The asymmetric ring-opening/cyclization of cyclopropyl ketones with primary amine nucleophiles was catalyzed by a chiral N,N'-dioxide/scandium(III) complex through a kinetic resolution process. A broad range of cyclopropyl ketones and primary amines are suitable substrates of this reaction. The corresponding products were afforded in excellent enantioselectivities and yields (up to 97% ee and 98% yield) under mild reaction conditions. This method provides a promising access to chiral 2,3-dihydropyrroles as well as an effective procedure for the kinetic resolution of 2-substituted cyclopropyl ketones.
Polystyrene-supported amino acids as efficient catalyst for chemical fixation of carbon dioxide
Four new polystyrene-supported amino acids have been synthesized and applied to the chemical fixation of carbon dioxide for the first time. Two series of experiments with polystyrene-supported threonine (PS-Thr) and polystyrene-supported tyrosine (PS-Tyr) as catalyst, respectively, were conducted to study the effect of the reaction conditions on the carboxylation of propylene oxide/carbon dioxide. There was no considerable decrease in the yield of propylene carbonate after the polystyrene-supported amino acids were used five times, indicating that these catalysts are very stable. It was demonstrated that these catalysts were very efficient in the carboxylation of various epoxides and aziridines with carbon dioxide under mild conditions without any solvents. The mechanism for this carboxylation is also discussed.
Qi, Chaorong,Ye, Jinwu,Zeng, Wei,Jiang, Huanfeng
supporting information; experimental part
p. 1925 - 1933
(2010/11/04)
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