Supercritical Carbon Dioxide as Solvent and Temporary Protecting Group for Rhodium-Catalyzed Hydroaminomethylation

Supercritical Carbon Dioxide as Solvent and Temporary Protecting Group for Rhodium-Catalyzed Hydroaminomethylation

Supercritical carbon dioxide (scCO2) acts simultaneously as solvent and temporary protecting group during homogeneously rhodium‐catalyzed hydroaminomethylation of ethyl methallylic amine. Cyclic amines are formed as the major products in scCO2, whereas the cyclic amide is formed preferentially in co...

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Bibliographic Details
Published in:Chemistry : a European journal Vol. 7; no. 21; pp. 4584 - 4589
Main Authors: Wittmann, Klaus, Wisniewski, Wolfgang, Mynott, Richard, Leitner, Walter, Kranemann, Christian Ludger, Rische, Thorsten, Eilbracht, Peter, Kluwer, Sander, Ernsting, Jan Meine, Elsevier, Cornelis J.
Format: Journal Article
Language:English
Published: Weinheim WILEY-VCH Verlag GmbH 05-11-2001
WILEY‐VCH Verlag GmbH
Subjects:
homogeneous catalysis
hydroaminomethylation
hydroformylation
protecting groups
supercritical fluids
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Summary:Supercritical carbon dioxide (scCO2) acts simultaneously as solvent and temporary protecting group during homogeneously rhodium‐catalyzed hydroaminomethylation of ethyl methallylic amine. Cyclic amines are formed as the major products in scCO2, whereas the cyclic amide is formed preferentially in conventional solvents. Multinuclear high‐pressure NMR spectroscopy revealed that this selectivity switch is mainly due to reversible formation of the carbamic acid in the solvent CO2, which reduces the tendency for intramolecular ring closure at the Rh–acyl intermediate. These results substantiate the general concept of using scCO2 as a protective medium for amines in homogeneous catalysis and demonstrate for the first time its application for selectivity control. A remarkably different product distribution from the hydroaminomethylation of ethyl methallylic amine 1 is observed when the reaction is carried out in supercritical carbon dioxide (scCO2) rather than in organic liquid solvents (see scheme): whereas the cyclic amide 3 is obtained as the major product in conventional solvents, saturated nitrogen heterocycles are formed preferentially in scCO2. The reaction conditions can be optimized further to yield either the pyrrolidine 2 or the new bicyclic framework 5 as the major saturated heterocyclic product.
Bibliography:istex:BFF2EF710E2DC11F84EA9D12EB5C8F185CA8538B
ArticleID:CHEM4584
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ObjectType-Article-1
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ObjectType-Feature-2
content type line 23
ISSN:0947-6539
1521-3765
DOI:10.1002/1521-3765(20011105)7:21<4584::AID-CHEM4584>3.0.CO;2-P