Preparation of indium nitronates and their Henry reactions
作者:Raquel G. Soengas、Rita Acúrcio、Artur M. S. Silva
DOI:10.1039/c4ob01468e
日期:——
Indium nitronates were readily prepared from commercially available nitroalkanes by transmetallation of the corresponding lithium nitronates with indium salts. The Henryreaction of this indium organometallics with aldehydes afforded β-nitroalkanols in moderate to high yields. The use of chiral sugar aldehydes furnished the corresponding carbohydrate-derived β-nitroalkanols with excellent stereoselectivity
Iminium-Allenamine Cascade Catalysis: One-Pot Access to Chiral 4H-Chromenes by a Highly Enantioselective Michael-Michael Sequence
作者:Xinshuai Zhang、Shilei Zhang、Wei Wang
DOI:10.1002/anie.200906050
日期:2010.2.15
Taking the Michael‐Michael: A cascadeMichael–Michael reaction of aryl or alkyl alkynals, involving an unprecedented iminium–allenaminesequence, is efficiently catalyzed by a chiral diphenylprolinol TBDMS ether, and affords highly functionalized 4H‐chromenes in high yields. TBDMS=tert‐butyldimethylsilyl.
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
Organocatalytic Asymmetric Tandem Michael Addition−Hemiacetalization: A Route to Chiral Dihydrocoumarins, Chromanes, and 4<i>H</i>-Chromenes
作者:Dengfu Lu、Yajun Li、Yuefa Gong
DOI:10.1021/jo101446d
日期:2010.10.15
Asymmetric tandem Michael addition−hemiacetalization between aliphatic aldehydes and (E)-2-(2-nitrovinyl)phenols was investigated for constructing benzopyran backbones. Interestingly, the diastereo- and enantioselectivities changed markedly when the reaction was mediated by different types of secondary amine catalysts. The diphenylprolinol silyl ether 7 promoted the reaction with excellent enantioselectivities
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%。