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 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 Sm(5)O(O-iPr)(13) showed broader substrate generality as well as higher reactivity and stereoselectivity compared to Sm(O-iPr)(3). The optimal system with Sm(5)O(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 Sm(5)O(O-iPr)(13).
Handa
Shinya
S
Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan.
Gnanadesikan
Vijay
V
Matsunaga
Shigeki
S
Shibasaki
Masakatsu
M
D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D007097:Imines / Q000138:chemical synthesis* / Q000737:chemistry; D008352:Mannich Bases / Q000737:chemistry; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D012493:Samarium / Q000737:chemistry*; D012545:Schiff Bases / Q000737:chemistry*; D013237:Stereoisomerism
D007097:Imines; D008352:Mannich Bases; D009942:Organometallic Compounds; D012545:Schiff Bases; D012493:Samarium; D003300:Copper