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

Abstract

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).

Conjugate addition nitro-Mannich reaction of carbon and heteroatom nucleophiles to nitroalkenes

“…They have been used in the synthesis of many nitrogen containing functional groups including α-amino carbonyls, 2, 3 1,2-diamines, [4][5][6][7] peptidomimetics, 8 natural products [9][10][11][12][13][14][15] and many heterocyclic small molecules. [16][17][18][19][20][21][22][23][24][25][26][27][28][29] To address the paucity of structurally diverse nitroalkanes we have developed conjugate addition nitro-Mannich protocols (Scheme 1). [30][31][32] The use of nitroalkenes (prepared via the Henry reaction) provides easy access to more structurally complex nitro coupling partners, thereby generating β-nitroamines with higher levels of functionality which may be further manipulated to produce a range of useful intermediates.…”

Multimetallic Multifunctional Catalysts for Asymmetric Reactions

“…Thus, both Cu and Sm are essential for high catalytic activity and selectivity. After optimization studies, the addition of achiral phenol source and the use of oxo-samarium alkoxide, Sm 5 O(O-iPr) 13 , with a well-ordered structure, gave the superior reactivity and stereoselectivity. Under the optimized reaction conditions, 1-10 mol% of the Cu/Sm catalyst promoted asymmetric nitro-Mannich-type reaction, giving products with good yield, high syn-selectivity, and enantioselectivity (Scheme 1) [13].…”

Syntheses, Structures, and Properties of Two Dicyanamide‐Bridged Polymers with a Schiff‐base Ligand

“…[1][2][3][4][5][6][7] Salen-type ligands are able to stabilize different metals in a large range of oxidation states and coordination environments. [8][9][10] A series of Salen-type ligands, which result from the reaction of 3-methoxysalicylaldehyde with different diamines have been employed to generate heterodinuclear 3d/ alkali-metal and 3d/4f complexes with the 3d ion coordinated in the N 2 O 2 site and the alkali metal cation or the 4f ion in the O 2 O 2 site, formulated as LMMЈX n or LMLnX n , where L stands for the ligands, M for 3d ions (mainly Zn 2+ , Ni 2+ , and Cu 2+ ), MЈ for alkali metal ions (mainly Na + , Li + , and K + ), Ln for 4f ions, and X for anionic species (n is the number of X).…”

“…Moreover, the metal-metal intra-and internode interactions can lead to new redox, electric, or magnetic properties. [27] Dicyanamide(dca), N(CN) 2 -, with its various coordination modes (shown in Scheme 1) such as μ 1,3 and μ 1,5 ing extended molecular architectures. Meanwhile, its versatile coordination behavior and ability to generate polymeric structures with diverse magnetic properties facilitated its use.…”