A synthetically useful source of propargyl radicals
摘要:
S-propargyl xanthates constitute a convenient source of propargyl radicals that can be captured in an inter- or intra-molecular fashion. Copyright (C) 1996 Published by Elsevier Science Ltd
Highly Enantioselective Intermolecular Hydroamination of Allylic Amines with Chiral Aldehydes as Tethering Catalysts
作者:Melissa J. MacDonald、Colin R. Hesp、Derek J. Schipper、Marc Pesant、André M. Beauchemin
DOI:10.1002/chem.201203462
日期:2013.2.18
Chirally LinkedIn: Chiralaldehydes are effective tetheringcatalysts for enantioselectiveintermolecularhydroamination, which provides access to vicinal diamine motifs in good yields and excellent enantioselectivities (see scheme). This work highlights simple chiral α‐oxygenated aldehydes as effective organocatalysts capable of efficiently inducing asymmetry through transient intramolecularity.
Studies on Imidazoles. IV.<sup>1</sup> The Synthesis and Antithyroid Activity of Some 1-Substituted-2-mercaptoimidazoles
作者:Reuben G. Jones、Edmund C. Kornfeld、Keith C. McLaughlin、Robert C. Anderson
DOI:10.1021/ja01180a036
日期:1949.12
Catalysis through Temporary Intramolecularity: Mechanistic Investigations on Aldehyde-Catalyzed Cope-type Hydroamination Lead to the Discovery of a More Efficient Tethering Catalyst
作者:Nicolas Guimond、Melissa J. MacDonald、Valérie Lemieux、André M. Beauchemin
DOI:10.1021/ja303320x
日期:2012.10.10
Mechanistic investigations on the aldehyde-catalyzed intermolecular hydroamination of allylic amines using N-alkylhydroxylamines are presented. Under the reaction conditions, the presence of a specific aldehyde catalyst allows formation of a mixed aminal intermediate, which permits intramolecular Cope-type hydroamination. The reaction was determined to be first-order in both the aldehyde catalyst (alpha-benzyloxyacetaldehyde) and the allylic amine. However, the reaction displays an inverse order behavior in benzylhydroxylamine, which reveals a significant off-cycle pathway and highlights the importance of an aldehyde catalyst that promotes a reversible aminal formation. Kinetic isotope effect experiments suggest that hydroamination is the rate-limiting step of this catalytic cycle. Overall, these results enabled the elaboration of a more accurate catalytic cycle and led to the development of a more efficient catalytic system for alkene hydroamination. The use of 5-10 mol % of paraformaldehyde proved more effective than the use of 20 mol % of a-benzyloxyacetaldehyde, leading to high yields of intermolecular hydroamination products within 24 h at 30 degrees C.