IAN-Amines: Direct Entry to a ChiralC2-Symmetric Zirconium(IV)β-Diketimine Complex

Abstract

The immense utility of metallocene-based catalysts for synthesis [1] has stimulated the development of non-metallocene complexes that conserve metallocene topographies but offer a greater degree of accessibility and/or improved performance. [2] A number of recent publications have demonstrated that amidinate ligands, [3,4] b-diketimines, [5±7] and other variations on the [1,n]-bisimine template are promising in this regard for group IV metals. In general, ligands used as the basis for a non-metallocene complex must 1) bind to the stereochemistry of 5 d was deduced clearly by means of X-ray crystallography. This tandem cyclization was also applied to allene ketones. Thus allene ketone 4 e was cyclized to give piperidyl-substituted alcohol 5 e in 67 % yield (Table 2, entry 5). However, the malonate substrate 4 f gave rise to cis-cyclohexanol 5 f (30 %) as well as the simple addition product 6 (35 %) ( Table 2, entry 6).The exact mechanism of this cis-stereoselective tandem reaction has yet to be elucidated. It is presumed that Me 3 SiPdSnBu 3 adds initially to the allene moiety to give sor p-allyl palladium complexes, which undergo intramolecular carbonyl allyl addition to afford cis-cycloalkanols. The cis selectivity of the reaction can be ascribed to the fact that intermediate A, which leads to the cis-cyclopentanol, is energetically more stable than B, presumably because of the steric hindrance between TMS and R (R H, Me) groups (Scheme 2). [11] In summary, the palladium-catalyzed regio-and diastereoselective tandem silastannylation/carbonyl allyl addition of allene aldehydes and ketones gives rise to cis-cycloalkanols. The process requires a single catalyst and is carried out at constant temperature. Experimetal SectionTypical procedure: trimethyl(tributylstannyl)silane 2 (150 mg, 0.41 mmol) was added to a stirred solution of 1 a (100 mg, 0.38 mmol) and (pallyl) 2 Pd 2 Cl 2 (6.9 mg, 5 mol %) in THF (3 mL). The reaction mixture was stirred room temperature for 10 min, and the THF solvent was evaporated in vacuo. The crude product was separated by means of column chromatography (EtOAc/hexane 1:2) to afford the cyclized product 3 a (91 mg, 71 %) as a white solid. M.p. 95 8C; R f 0.41 (EtOAc/hexane 1:2); The condensation of allylic stannanes and aldehydes catalyzed by the known palladium and platinum complexes was primarily limited to simple allylic stannanes and crotyl stannanes; see: H.

Rhodium-Catalyzed Atroposelective Oxidative C–H/C–H Cross-Coupling Reaction of 1-Aryl Isoquinoline Derivatives with Electron-Rich Heteroarenes

“…Axially chiral biaryls are important structural motifs in natural products, functional materials, medicinal chemistry, privileged catalysts, and ligands. − Many elegant methods have been developed to access these axially chiral biaryls. , Recently, asymmetric C–H functionalization reactions have been established as an increasingly important strategy for the synthesis of axially chiral biaryls. − To be noted, among these previous reports, functionalized arenes such as aryl halides, aryl organometallic reagents, and diazo compounds were generally used (Scheme A). Thus, we envisaged that enantio­selective two-fold oxidative C–H cross-coupling reactions between two arenes would provide direct access to atrop­isomeric biaryls (Scheme B). Herein, we report the details of this study.…”

Palladium-Catalyzed Aminocarbonylation of Isoquinolines Utilizing Chloroform-COware Chemistry

“…For the synthesis of 1-amino-4-iodoisoquinolines 3c – e , isoquinoline 2 was transformed to isoquinoline 2-oxide 5 using m -CPBA, followed by C-1 chlorination involving POCl 3 ( 8a ) . Then, C-1 amination was achieved utilizing various amines and triethylamine in DMF at 150 °C ( 9a – c ).…”

“…1-Chloro-4-iodoisoquinoline was prepared according to literature procedures . To a dry round-bottom flask containing a magnetic bead was added crude 4-iodoisoquinoline 2-oxide 4 (170 mg) in POCl 3 (2 mL) under an ice-cold condition, and the reaction mixture was stirred for 15 min.…”

Synthesis and Characterization of New Chiral Monoanionic [ON] Ancillary Phenolate Ligands

“…However, given their widespread application, it is somewhat surprising that the chiral variants of aminophenolate ligands are relatively lacking in the literature. The introduction of an aromatic ring in the pendant side arm, the resonance in the backbone is attenuated in comparison with the regular ligands and this may offer some unique opportunities for electronic differentiation and stereocontrol upon coordination [47]. Of particular interest are ligands with chiral pendant substituents that are in close proximity with the open coordination site at the periphery where catalysis occurs.…”