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Ruthenium‐Catalyzed Chemoselective N‐Allyl Cleavage: Novel Grubbs Carbene Mediated Deprotection of Allylic Amines
Author(s) -
Alcaide Benito,
Almendros Pedro,
Alonso Jose M.
Publication year - 2003
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/chem.200305236
Subject(s) - allylic rearrangement , carbene , chemistry , ruthenium , isomerization , catalysis , grubbs' catalyst , combinatorial chemistry , palladium , organic chemistry , metathesis , medicinal chemistry , polymerization , polymer
A novel application of the Grubbs carbene complex has been discovered. The first examples of the catalytic deprotection of allylic amines with reagents other than palladium catalysts have been achieved through Grubbs carbene mediated reaction. Significantly, the catalytic system directs the reaction toward the selective deprotection of allylic amines (secondary as well as tertiary) in the presence of allylic ethers. A variety of substrates, including enantiomerically pure multifunctional piperidines, are also usable. The new method is more convenient, chemoselective, and operationally simple than the palladium‐catalyzed method. The current mechanistic hypothesis invokes a nitrogen‐assisted ruthenium‐catalyzed isomerization, followed by hydrolysis of the enamine intermediate. We believe that the reactive species involved in the reaction may be an RuH species rather than the Grubbs carbene itself. Thus, the isomerization may occur according to the hydride mechanism. The synthetic utility of this ruthenium‐catalyzed allyl cleavage is illustrated by the preparation of indolizidine‐type alkaloids.