Synthesis of New Chiral 2,2‘-Bipyridyl-Type Ligands, Their Coordination to Molybdenum(0), Copper(II), and Palladium(II), and Application in Asymmetric Allylic Substitution, Allylic Oxidation, and Cyclopropanation

Abstract

A series of chiral bipyridine-type ligands 5-12 has been synthesized via a de novo construction of the pyridine nucleus. The chiral moieties of the ligands originate from the monoterpene realm, namely, pinocarvone (13 f 6, 7, and 9), myrtenal (18 f 5), nopinone (21 f 8 and 10), and menthone (28 f 11 and 12); the first three precursors can be obtained in one step from -and R-pinene, respectively. Complexes of these ligands with molybdenum(0) (38-40) and copper(II) (41) have been characterized by single-crystal X-ray crystallography. While complex 38 exhibits polymorphism (monoclinic and tetragonal forms crystallize from the same batch), 41 is characterized by a tetrahedrally distorted geometry of the metal coordination. The Mo and Pd complexes exhibit modest asymmetric induction in allylic substitution (43 f 44), and the Cu(I) counterpart of 41, derived from 10 (PINDY) and Cu(OTf) 2 , shows promising enantioselectivity (49-75% ee) and reaction rate (g30 min at room temperature) in allylic oxidation of cyclic olefins (47 f 48). The Cu(I) complex of 11 (MINDY) proved effective in cyclopropanation (49 f 50) with up to 72% ee.

Microwave Assisted Synthesis of Molybdenum and Tungsten Tetracarbonyl Complexes with a Pyrazolylpyridine Ligand. Crystal structure of cis-[Mo(CO)4{ethyl[3-(2-pyridyl)-1-pyrazolyl]acetate}]

“…The IR spectra of 1 and 2 show four active ν(C≡O) normal modes in the 1810-2015 cm - [24,25], those containing organic ligands with N-aromatic donor atoms are far less common. Most of the reported structures belonging to this family contain either 2-pyridyl substituted ligands [26][27][28][29][30][31][32][33][34][35][36][37][38], 2,2'-bipyridine [39][40][41][42][43][44][45][46] or 1,10-phenanthroline [47,48] (and their derivatives). Thiel and co-workers described two structures for tetracarbonyl complexes of molybdenum chelated by 2-(3-pyrazolyl)pyridine residues [22,49].…”

Mechanistic Insights into Stereoselective Catalysis—The Effects of Counterions in a CuII–Bissulfoximine‐Catalyzed Diels–Alder Reaction

“…This has also been observed for other types of catalytic systems. [39] Further investigations are necessary to establish if this is a general requirement for homogeneous enantioselective catalysis. À1 ) monochromator was used for the copper and bromine edges.…”

Kupfer‐Carben‐Komplexe: hochentwickelte Katalysatoren, neue Erkenntnisse

“…B. Semicorrine (!22), [22a, 24] Polypyrazolylborate (!24) [25,26] und Iminophosphanamidate (!25). [27] Kationische Komplexe erhält man mit Bipyridinen (!27), [28][29][30][31][32] Phenanthrolinen [30,33] und Terpyridinen. [30,34,35] Die häufig verwendeten Bisoxazoline geben neutrale Komplexe 23 [22b, 36] oder kationische Komplexe 26, [37] je nach Art der 2,2'-Verknüpfung.…”