Enantioselective Syntheses of Morpholines and Their Homologues via S<sub>N</sub>2-Type Ring Opening of Aziridines and Azetidines with Haloalcohols
作者:Manas K. Ghorai、Dipti Shukla、Kalpataru Das
DOI:10.1021/jo901297d
日期:2009.9.18
yield and enantioselectivity of a variety of substituted nonracemic morpholines and their homologues is described. The reaction proceeds via an SN2-type ring opening of activated aziridines and azetidines by suitable halogenated alcohols in the presence of Lewis acid followed by base-mediated intramolecular ring closure of the resulting haloalkoxy amine.
aza-Michael addition of N-substituted phosphoramidates to enones generates aza-Michael adducts which undergo intramolecular reductive cyclization with (R)-alpine borane to afford 1,2,4-trisubstituted azetidines in a one-pot procedure. These optically active products are obtained in good to high yields (67–93%) with excellent stereocontrol (78–96% ee) from a vast variety of enones.
Syntheses of Chiral β- and γ-Amino Ethers, Morpholines, and Their Homologues via Nucleophilic Ring-Opening of Chiral Activated Aziridines and Azetidines
作者:Manas K. Ghorai、Dipti Shukla、Aditya Bhattacharyya
DOI:10.1021/jo300002u
日期:2012.4.20
Lewis acid catalyzed quaternary ammonium salt mediated highly regioselective ring-opening of chiral activated aziridines and azetidines with alcohols to nonracemic β- and γ-amino ethers has been developed. The reaction mainly proceeds via an SN2 pathway, and the partial racemization of the starting substrate was effectively controlled by using quaternary ammonium salts. β- and γ-amino ethers are obtained
已经开发了路易斯酸催化的季铵盐介导的手性活化氮丙啶和氮杂环丁烷与醇的非区域性β-和γ-氨基醚的高度区域选择性开环。该反应主要通过S N 2途径进行,并且通过使用季铵盐有效地控制了起始底物的部分消旋。以高对映体和非对映体特异性(ee最高> 99%,最高99%)获得β-和γ-氨基醚。当将卤代醇用作亲核试剂时,该方法进一步扩展为合成具有高对映体特异性的吗啉及其同系物(ee高达90%)。
A convenient synthetic route to enantiopure N-tosylazetidines from α-amino acids
作者:Manas K. Ghorai、Kalpataru Das、Amit Kumar
DOI:10.1016/j.tetlet.2007.02.033
日期:2007.4
A general and convenient syntheticroute to various chiral 2-substituted- and 2,4-disubstituted-N-tosylazetidines (ee >99%) is described in good overall yields starting from chiral α-amino acids using very simple chemistry.
Lewis Acid-Mediated Unprecedented Ring-Opening Rearrangement of 2-Aryl-<i>N</i>-tosylazetidines to Enantiopure (<i>E</i>)-Allylamines
作者:Manas K. Ghorai、Amit Kumar、Kalpataru Das
DOI:10.1021/ol7023218
日期:2007.12.1
of 2-aryl-N-tosylazetidines in polar and coordinating solvents followed by an unprecedented rearrangement to substituted achiral and chiral (E)-allylamines (ee >99%) is reported. The methodology has been applied for the synthesis of gamma-unsaturated-beta-amino acids. A plausible mechanism for the rearrangement is also described.