Aminoboranes as "Compatible" Iminium Ion Generators in Aminative C-C Bond Formations
Michinori Suginome,* Lars Uehlin, and Masahiro Murakami
*Department of Synthetic Chemistry and Biological Chemistry, Graduate School
of Engineering, Kyoto University, Email: suginome
sbchem.kyoto-u.ac.jp
M. Suginome, L. Uehlin, M. Murakami, J. Am. Chem. Soc., 2004, 126, 13196-13197.
DOI: 10.1021/ja045827y
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Abstract
Aminoboranes are highly efficient and mild iminium ion generators in the Mannich-type aminative coupling of aldehydes with silyl ketene acetals. The use of diisopropylaminoboranes enables a three-component Mannich reaction of free secondary amines with aldehydes and silyl ketene acetals.
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Details
The document discusses the development of aminoboranes as efficient iminium ion generators for Mannich-type reactions, which are crucial for forming functionalized amines. Traditional three-component Mannich reactions involve amines, non-enolizable aldehydes, and active methylene compounds under harsh acidic conditions. Recent advancements have improved the reaction efficiency using two-component systems with preformed imines or iminium salts. However, a three-component strategy is preferred for synthesizing diverse derivatives due to the in situ formation of iminium intermediates from aldehydes and amines.
The authors report a new three-component Mannich-type reaction using aminoboranes, which are compatible with acid-sensitive functionalities and work under mild conditions. Experiments showed that aminoboranes, particularly the salicyl alcohol derivative, effectively generated iminium intermediates, leading to high yields of β-amino esters. The presence of a secondary amide like 2-piperidinone further accelerated the reaction.
The study also demonstrated the reaction's applicability to various aldehydes and silyl ketene acetals, producing Mannich products in high yields. The use of free secondary amines via in situ aminoborane formation was also successful. This method's mild conditions and compatibility with functional groups make it a valuable tool for synthetic chemistry.
Y. Tanaka, T. Hasui, M. Suginome, Synlett, 2008, 1239-1241.
Key Words
β-Amino Acids, Mannich Reaction, Multicomponent Reactions
ID: J48-Y2004-1750
