Synthesis of New Chiral 2,2‘-Bipyridine Ligands and Their Application in Copper-Catalyzed Asymmetric Allylic Oxidation and Cyclopropanation

Abstract

A series of modular bipyridine-type ligands 1 and 3-9 has been synthesized via a de novo construction of the pyridine nucleus. The chiral moieties of these ligands originate from the isoprenoid chiral pool, namely, beta-pinene (10 --> 1), 3-carene (14 --> 3 and 5), 2-carene (28 --> 4), alpha-pinene (43 --> 6-8), and dehydropregnenolone acetate (48 --> 9), respectively. Copper(I) complexes, derived from these ligands and (TfO)(2)Cu (1 mol %) upon an in situ reduction with phenylhydrazine, exhibit good enantioselectivity (up to 82% ee) and unusually high reaction rate (typicaly 30 min at room temperature) in allylic oxidation of cyclic olefins (52 --> 53). Copper-catalyzed cyclopropanation proceeded with < or =76% enantioselectivity and approximately 3:1 to 99:1 trans/cis-diastereoselectivity (54 --> 55 + 56). The level of the asymmetric induction is discussed in terms of the ligand architecture that controls the stereochemical environment of the coordinated metal.

Chiral Bis(pyridylimino)isoindoles: A Highly Modular Class of Pincer Ligands for Enantioselective Catalysis

“…[9] A series of constitutional isomers of 2 a-c, compounds 3 a-c (denoted pinbpi), was obtained by using 1 b, which was derived from (À)-bpinene, [10] and the (+)-2-carene-derived series (4 a-c; denoted carbpi) was prepared from 1 c, which was synthesized from the corresponding 2-triflatopyridine (see the Supporting Information). [11] The bpi ligands for each of the three series were used for the preparation of iron(II) and cobalt(II) acetato complexes 5 a-9 c (Scheme 2) by either direct complexation of the metal diacetate or by reaction with the corresponding dichloride with subsequent anion exchange. All metal compounds are assumed to adopt distorted octahedral coordination geometries with one solvent molecule (MeOH or THF) occupying the sixth coordination site as indicated by the mass spectrometric and analytical data.…”

Synthesis of (R)- and (S)-2-N-methylamino-2,3-dimethylbutanamides and (R)- and (S)-(5-isopropyl-1,5-dimethyl-4,5-dihydro-1H-imidazol-4-on-2-yl)pyridines

“…The mixture obtained was extracted with CH2Cl2 (3 × 70 ml), and the combined extracts were evaporated until dry. The crude product was made rid of benzyl alcohol in vacuum at 110 °C and then recrystallized from a mixture of cyclohexane and CHCl3 (10: (m,2H,PyH3,5),8.85 (m,1H,PyH6). 13 C NMR (DMSO-d6, δ ppm): 15.1; 16.5; 19.3; 30.5; 32.5; 71.6; 126.6; 126.8; 137.7; 148.6; 149.0; 173.9; 192.6 …”

Biotransformation of bicyclic terpenoid ketones towards compounds with olfactory properties

“…The yield and composition of reaction mixture strongly depends on both used catalyst and its stoichiometry to the substrate. [14,15] The aim of our studies was to obtain (−)-3-carene-2,5-dione, 2, and (+)-3-carene-5-one, 3, from (+)-3-carene in a one-step reaction. The next step was the biotransformations of 2 and 3 using Aspergillus niger, Hansenula anomala, Fusarium oxysporum, Fusarium culmorum, Streptomyces lusitanus StA.…”