Scope and Mechanism of Enantioselective Michael Additions of 1,3-Dicarbonyl Compounds to Nitroalkenes Catalyzed by Nickel(II)−Diamine Complexes

Abstract

Readily prepared Ni(II)-bis[(R,R)-N,N'-dibenzylcyclohexane-1,2-diamine]Br(2) was shown to catalyze the Michael addition of 1,3-dicarbonyl compounds to nitroalkenes at room temperature in good yields with high enantioselectivities. The two diamine ligands in this system each play a distinct role: one serves as a chiral ligand to provide stereoinduction in the addition step while the other functions as a base for substrate enolization. Ligand modification within the catalyst was also investigated to facilitate the reaction of aliphatic nitroalkenes, 1,3-diketones, and beta-ketoacids. Ni(II)-bis[(R,R)-N,N'-di-p-bromo-benzylcyclohexane-1,2-diamine]Br(2) was found to be an effective catalyst in these instances. Furthermore, monodiamine complex, Ni(II)-[(R,R)-N,N'-dibenzylcyclohexane-1,2-diamine]Br(2), catalyzed the addition reaction in the presence of water. The proposed model for stereochemical induction is shown to be consistent with X-ray structure analysis.

Synthesis and Applications of (-)-(S)-3-Aminoquinuclidine- Derived Thiourea

“…The NMR data and other characteristics of products 13 fully correspond to those reported earlier [10]. The enantiomeric excess and the absolute configuration of the product was determined by comparing the specific rotation of 13 with that of literature data [10]. D. To a solution of 1,3-diphenyl-2-propen-1-one 10 (60.0 mg, 0.289 mmol, 1.0 equiv) and catalyst 2 (12.0 mg, 0.029 mmol, 0.1 equiv) in toluene (0.2 ml) nitromethane 8 (46.0 μl, 0.85 mmol, 3 equiv) was added.…”

“…The residue was purified by column chromatography (ethyl acetate/hexanes 4 %) and yielded product 13. The NMR data and other characteristics of products 13 fully correspond to those reported earlier [10]. The enantiomeric excess and the absolute configuration of the product was determined by comparing the specific rotation of 13 with that of literature data [10].…”

“…The reaction 6 + 9 → 13 in the presence of 10 mol-% of 2 in solvent mixture toluenetetrahydrofuran/CH 2 Cl 2 afforded the desired Michael adduct (17 % conversion by gas chromatography-mass spectrometry (GC-MS)) with (S)-isomer being the major enantiomer (23 % ee). The absolute configuration of the isolated product 13 was determined by comparing the specific rotation ([α] D 23 = 1.7 (c = 0.6, CHCl 3 ) with that of literature data [10]. …”

Enantioselective addition of aryl ketones and acetone to nitroalkenes organocatalyzed by carbamate-monoprotected cyclohexa-1,2-diamines

“…3-(benzo[d][1,3]dioxol-5-yl)-4-nitro-1-phenylbutan-1-one (6ad). 23 4-nitro-1-phenyl-3-(pyridin-3-yl) …”

Ferric chloride-catalyzed decarboxylative alkylation of β-keto acids with benzylic alcohols

“…Melting points were un-corrected. Alcohols [26,28] and β-keto acids [1,10,29] were prepared according to known procedures, and the rest of chemicals were purchased and used as received. The solvents were dried over anhydrous magnesium sulfate prior to use.…”