Heterobimetallic Transition Metal/Rare Earth Metal Bifunctional Catalysis: A Cu/Sm/Schiff Base Complex for Syn-Selective Catalytic Asymmetric Nitro-Mannich Reaction

The full details of a catalytic asymmetric syn-selective nitro-Mannich reaction promoted by heterobimetallic Cu/Sm/dinucleating Schiff base complexes are described, demonstrating the effectiveness of the heterobimetallic transition metal/rare earth metal bifunctional catalysis. The first-generation...

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Bibliographic Details
Published in:Journal of the American Chemical Society 2010-04, Vol.132 (13), p.4925-4934
Main Authors: Handa, Shinya, Gnanadesikan, Vijay, Matsunaga, Shigeki, Shibasaki, Masakatsu
Format: Article
Language:English
Subjects:
Catalysis
Copper - chemistry
Imines - chemical synthesis
Imines - chemistry
Mannich Bases - chemistry
Molecular Structure
Organometallic Compounds - chemistry
Samarium - chemistry
Schiff Bases - chemistry
Stereoisomerism
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Summary:The full details of a catalytic asymmetric syn-selective nitro-Mannich reaction promoted by heterobimetallic Cu/Sm/dinucleating Schiff base complexes are described, demonstrating the effectiveness of the heterobimetallic transition metal/rare earth metal bifunctional catalysis. The first-generation system prepared from Cu(OAc)2/Sm(O-iPr)3/Schiff base 1a = 1:1:1 with an achiral phenol additive was partially successful for achieving the syn-selective catalytic asymmetric nitro-Mannich reaction. The substrate scope and limitations of the first-generation system remained problematic. After mechanistic studies on the catalyst prepared from Sm(O-iPr)3, we reoptimized the catalyst preparation method, and a catalyst derived from Sm5O(O-iPr)13 showed broader substrate generality as well as higher reactivity and stereoselectivity compared to Sm(O-iPr)3. The optimal system with Sm5O(O-iPr)13 was applicable to various aromatic, heteroaromatic, and isomerizable aliphatic N-Boc imines, giving products in 66−99% ee and syn/anti = >20:1−13:1. Catalytic asymmetric synthesis of nemonapride is also demonstrated using the catalyst derived from Sm5O(O-iPr)13.
ISSN:0002-7863
1520-5126
DOI:10.1021/ja100514y