Synthesis of Stereoprojecting, Chiral N-C(sp³)-E Type Pincer Complexes

Abstract

A synthetic strategy to generate chiral N-C­(sp3)-E (E = S, O) pincer complexes incorporating enhanced stereoprojecting groups at the N-arm site has been established. The synthesis of the tridentate pincer ligand was carried out via palladacycle-catalyzed asymmetric hydrophosphination of N-chelating enones. The chelation properties of the substrates were initially demonstrated on C­(sp2)-N type palladacycles. The extended substrate scope allows versatile structural modifications on the ligand backbone. Subsequent cyclometalation provided N-C­(sp3)-E complexes in a diastereoselective reaction.

Asymmetric addition of P-H compounds to unsaturated carbonyl derivatives

“…In the addition of diphenyl phosphane (17) to quinoline-based unsaturated compounds (e.g., 1, R 1 = quinolin-2-yl R 2 = Ph), catalyst 24 proved to be superior to complex 28 and generated enantiomeric excess up to 97% (Table 8, entry 9). 32 In the second step of the reaction, sulfur, not hydrogen peroxide, was used to prepare air-stable pentavalent P-derivatives (P=S analogues of 22). When the quinoline ring was replaced by a pyridine moiety (1, R 1 = pyridin-2-yl, R 2 = Ph), enantiomeric excess remained excellent (97% ee, Table 8, entry 10).…”

Squaramide-catalyzed enantioselective Michael addition of nitromethane to 2-enoylazaarenes: synthesis of chiral azaarene-containing γ-nitroketones

“…In recent decades, substantial focus has been directed towards the utilization of 2enoylpyridines and their N-oxides for a variety of asymmetric transformations. In particular, the enantioselective Michaeltype reactions catalyzed by organometallic complexes [8][9][10][11][12][13][14][15][16][17][18] and organocatalysts [19][20][21][22][23][24][25][26][27][28][29][30] have gained much more attention. Of the current catalytic systems, bifunctional chiral squaramides and (thio)ureas have emerged as undoubtedly the privileged catalysts for organocatalytic conjugate addition reactions between 2-enoylpyridines and various carbanion nucleophiles, including malononitrile, nitroalkanes, 1,3-dicarbonyl compounds, and so on (Scheme 1a).…”

Exploring the Interaction of Pyridine-Based Chalcones with Trinuclear Silver(I) Pyrazolate Complex

“…Based on the ability of trinuclear metal pyrazolates to form complexes with compounds possessing carbonyl groups and basic nitrogen atoms, the pyridine-containing chalcones were chosen as agents for the complexation with silver(I) trinuclear macrocycle ([AgPz] 3 , Pz = 3,5-bis(trifluoromethyl)pyrazolate anion). The ability of pyridine-chalcones to chelate metal ions is known because this class of compound has been suggested as a structural analog of bipyridine-type ligands [47][48][49][50].…”