Highly Enantioselective α Alkylation of Aldehydes with 1,3-Benzodithiolylium Tetrafluoroborate: A Formal Organocatalytic α Alkylation of Aldehydes by the Carbenium Ion
作者:Andrea Gualandi、Enrico Emer、Montse Guiteras Capdevila、Pier Giorgio Cozzi
DOI:10.1002/anie.201102562
日期:2011.8.16
A formal formyl: The organocatalytic stereoselective addition of formyl equivalents to aldehydes (see scheme) tolerates a large variety of functional groups to afford products with high enantioselectivity (92–97 % ee) and good yields (up to 95 %). The benzodithiol group can be easily removed with Raney Ni or metalated with nBuLi, thus giving access to a methyl group or to a wide range of useful intermediates
Iminium ion cascade reactions: stereoselective synthesis of quinolizidines and indolizidines
作者:Shawn M. Amorde、Ivan T. Jewett、Stephen F. Martin
DOI:10.1016/j.tet.2008.10.074
日期:2009.4
A noveliminiumion cascade reaction has been developed that allows for the stereoselective synthesis of a variety of substituted aza-fused bicycles. The combination of amino allylsilanes and aldehydes (or ketones) was used to synthesize a number of quinolizidines and indolizidines in a one-pot reaction sequence. This technology has been used to effect the facile syntheses of several indolizidine and
Bioinspired Divergent Oxidative Cyclizations of Geissoschizine: Total Synthesis of (–)‐17‐nor‐Excelsinidine, (+)‐16‐
<i>epi</i>
‐Pleiocarpamine, (+)‐16‐Hydroxymethyl‐Pleiocarpamine and (+)‐Taberdivarine H
作者:Maxime Jarret、Aurélien Tap、Victor Turpin、Natacha Denizot、Cyrille Kouklovsky、Erwan Poupon、Laurent Evanno、Guillaume Vincent
DOI:10.1002/ejoc.202000962
日期:2020.10.31
To synthesize excelsinidines and mavacurans alkaloids, bio‐inspired oxidativecyclizations of (+)‐geissochizine and analogues mediated by KHMDS/I2 were studied. Applied to geissoschizine, the N4–C16 bond formation led to excelsinidines core. Quaternization of the aliphatic nitrogen was necessary to access the mavacurans core (N1–C16 bond). Alternatively, 17‐nor‐excelsinidine was synthetized via an
为了合成excelsinidines和mavacurans生物碱,研究了由KHMDS / I 2介导的(+)-geissochizine及其类似物的生物启发性氧化环化作用。应用于Geissoschizine时,N4-C16键的形成导致了Excelsinidines的核心。脂族氮的季铵化是进入马六甲聚糖核心(N1-C16键)所必需的。或者,通过α-氯内酰胺的分子内亲核取代合成17-或excelsinidine。
The Cyano Group as a Traceless Activation Group for the Intermolecular [3+2] Cycloaddition of Azomethine Ylides: A Five-Step Synthesis of (±)-Isoretronecanol
The cyano group was used as a traceless activation group for the [3+2] cycloaddition of azomethine ylides in a two‐step process, thereby providing a highly effective approach to 5‐unsubstituted pyrrolidines. The transformation includes the silver acetate catalyzed intermolecular 1,3‐dipolarcycloaddition of α‐iminonitriles and an unprecedented sodium borohydride induced reductive decyanation reaction
Development of a s<i>yn</i>-Selective Mannich Reaction of Aldehydes with Propargylic Imines by Dual Catalysis: Asymmetric Synthesis of Functionalized Propargylic Amines
coupling of enolizable aldehydes with C‐alkynyl imines is realized affording the corresponding propargylic Mannich adducts of syn configuration, thus complementing previous methods that gave access to the anti‐isomers. The combination of proline and a urea Brønsted base cocatalyst is key for the reactions to proceed under very mild conditions (3–10 mol % catalyst loading, dichloromethane as solvent