Asymmetric Organocatalytic Cascade Michael/Hemiketalization/Retro-Aldol Reaction of 2-[(<i>E</i>)-2-Nitrovinyl]phenols with 2,4-Dioxo-4-arylbutanoates: A Convenient Access to Chiral α-Keto Esters
unprecedented organocatalyticenantioselective cascade Michael/hemiketalization/retro‐aldol reaction of 2‐[(E)‐2‐nitrovinyl]phenols and 2,4‐dioxo‐4‐arylbutanoates is described. With a bifunctional squaramide catalyst incorporating (1R,2R)‐1,2‐diphenylethane‐1,2‐diamine, the reactions afford products in 75–99% yields with 80–98% ee. This process provides an enantioselective pathway for the synthesis of chiral
Stereocontrolled construction of 3H-furo[3,4-b]chromen-1(9H)-one scaffolds via organocatalyzed Michael addition and the following intramolecular dehydration
An efficient approach for the stereocontrolledconstruction of 3H-furo[3,4-b]chromen-1(9H)-oneskeleton has been successfully developed through a sequential Michael addition/intramolecular dehydration strategy. The Michael addition of tetronic acid to 2-((E)-2-nitrovinyl)phenols catalyzed by a bifunctional squaramide derived from L-tert-leucine, and the subsequent intramolecular dehydration promoted
通过顺序迈克尔加成/分子内脱水策略,成功开发了一种立体控制3 H-呋喃并[3,4- b ] chromen-1(9 H)-骨架的有效方法。迈克尔加成特窗酸的2 - ((Ë)-2-硝基乙烯基)苯酚通过衍生自双官能squaramide催化大号-叔-亮氨酸,和由浓硫酸促进了随后的分子内脱水,顺利进行,得到相应的药学上有价值的3 H-呋喃并[3,4- b ] chromen-1(9 H)-one,可接受的收率为ee的79–97%。
Neighboring<i>ortho</i>-Hydroxy Group Directed Catalytic Asymmetric Triple Domino Reactions of Acetaldehyde with (<i>E</i>)-2-(2-Nitrovinyl)phenols
作者:Dhevalapally B. Ramachary、P. Srinivasa Reddy、M. Shiva Prasad
DOI:10.1002/ejoc.201402182
日期:2014.5
neighboring ortho-hydroxy group participation in the pretransition state of enamine- and iminium-based tripledominoreactions for high reactions rates and asymmetric induction. Enantiomerically pure, drug-like chromanes and tetrahydro-6H-benzo[c]chromenes having three to four contiguous stereocenters are synthesized through tripledomino Michael/aldol/oxa-Michael reactions catalyzed by (R)-2-diphenyl[(trim
Dienamineactivation wins against oxa‐1,4/1,4: By using nitrovinyl phenols and enals, aminocatalysis allows the asymmetricsynthesis of chromans and dihydrocoumarins bearing a CC double bond at the 3‐position (see scheme; TMS=trimethylsilyl). The new protocol takes advantage of the dienamine reactivity of the enal and avoids the known oxa‐Michael/Michael sequence.
A primary amine-thiourea organocatalyzed intramolecular Michaeladdition access was developed for the synthesis of trans-dihydrobenzofurans. Under the catalysis of an (R,R)-1,2-diphenylethylamine derived primary amine-thiourea bearing a glucosyl scaffold, the corresponding trans-dihydrobenzofurans were obtained in high yields with excellent level of enantioselectivities (94 to >99% ee). Moreover, an