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Supercritical Carbon Dioxide as Solvent and Temporary Protecting Group for Rhodium‐Catalyzed Hydroaminomethylation
Author(s) -
Wittmann Klaus,
Wisniewski Wolfgang,
Mynott Richard,
Leitner Walter,
Kranemann Christian Ludger,
Rische Thorsten,
Eilbracht Peter,
Kluwer Sander,
Ernsting Jan Meine,
Elsevier Cornelis J.
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20011105)7:21<4584::aid-chem4584>3.0.co;2-p
Subject(s) - chemistry , rhodium , catalysis , selectivity , amide , supercritical carbon dioxide , solvent , carbamic acid , supercritical fluid , amine gas treating , organic chemistry , intramolecular force , protecting group , combinatorial chemistry , polymer chemistry , alkyl
Supercritical carbon dioxide (scCO 2 ) 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 scCO 2 , 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 CO 2 , which reduces the tendency for intramolecular ring closure at the Rh–acyl intermediate. These results substantiate the general concept of using scCO 2 as a protective medium for amines in homogeneous catalysis and demonstrate for the first time its application for selectivity control.