Cycloaddition of homochiral imidazolinium ylides: A route to optically active pyrroloimidazoles
摘要:
The synthesis of either enantiomer of 1-benzyl-4-phenyl-2-imidazoline from phenylglycine is described. 'One-pot' generation and enantioselective 1,3-dipolar cycloaddition of homochiral azomethine ylides prepared from these imidazolines with a range of alkene dipolarophiles affords optically active hexahydropyrroloimidazole adducts.
The synthesis of an enantiomeric pair of enaminoesters from phenylglycine is described. Conjugate addition to alpha,beta-enones, reductive cyclization-fragmentation to octahydroimidazopyridines and further reduction to remove the auxiliary atoms, completes a new route to homochiral piperidines in which the enaminoesters function as homochiral 'ethanal enamines'.
Methylene-Bridged Bis(imidazoline)-Derived 2-Oxopyrimidinium Salts as Catalysts for Asymmetric Michael Reactions
作者:Andrey E. Sheshenev、Ekaterina V. Boltukhina、Andrew J. P. White、King Kuok Mimi Hii
DOI:10.1002/anie.201300614
日期:2013.7.1
In nothing flat: The title salts, having planar nitrogen centers, were utilized successfully as phase‐transfer catalysts for asymmetricMichaelreactions of tert‐butyl glycinate benzophenone Schiff base with vinyl ketone and chalcone derivatives, thus providing excellent levels of diastereo‐ and enantiocontrol (see scheme).
Cycloaddition of homochiral dihydroimidazoles: A 1,3-dipolar cycloaddition route to optically active pyrrolo[1,2-a]imidazoles
作者:Raymond C. F. Jones、Kevin J. Howard、John S. Snaith、Alexander J. Blake、Wang-Shei Li、Peter J. Steel
DOI:10.1039/c0ob00529k
日期:——
terminating in a 1,3-dipolarcycloadditionreaction that affords optically active pyrrolo[1,2-a]imidazoles. Three bonds of the so-formed pyrrolidine moiety are constructed in this cascade. The cycloaddition follows an endo approach of dipole and dipolarophile with anti geometry of the dipole and facial selectivity derived from the phenyl substituent. Inter- and intramolecularcycloaddition modes are observed
N-光学活性的烷基化1-苄基-4-苯基-4,5-二氢咪唑活性烷基卤化物和在一系列缺电子的烯烃双极性亲和剂存在下用DBU处理如此形成的4,5-二氢咪唑鎓离子,构成终止于1,3-偶极环加成反应的``一锅''级联反应提供光学活性的吡咯并[1,2- a ]咪唑。在该级联反应中构建了如此形成的吡咯烷部分的三个键。环加成遵循内偶极子和亲偶极与方法抗偶极子的几何形状,并从苯基取代基衍生的面部选择性。观察到分子间和分子内的环加成模式。
Synthesis of Chiral C2-Symmetric Methylene- and Boron-Bridged Bis(imidazolines)
by lithiation of 2-imidazolines and subsequent reaction with dialkyl- or diarylhaloboranes. The corresponding 2-imidazolines were prepared by an efficient four-step sequence starting from N-tert-butoxycarbonyl-protected α-amino acids. C 2 -Symmetric methylenebis(imidazolines) were readily synthesized from chiral diamines by condensation with diethyl malonimidate. The bis(imidazolines) were used as