Bis(pyridyl)silane and -methanol ligands. 3. A new class of optically active ligands prepared from readily available chiral 2-bromo-6-alkoxypyridines and their application in rhodium-catalyzed hydrosilations and copper(II)-catalyzed cyclopropanations

Journal Article · Sun Dec 31 23:00:00 EST 1989 · Organometallics; (USA)

DOI:https://doi.org/10.1021/om00115a022· OSTI ID:6654680

Wright, M E; Svejda, S A; Jin, Myungjong; Peterson, M A ^[1]

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1. Utah State Univ., Logan (USA)

Several chiral 2-bromo-6-alkoxypyridines (2) were prepared from the treatment of 2,6-dibromopyridine with the appropriate potassium alkoxide (alkoxides used: methoxide, myrtanoxide, myrtenoxide, isopinocampheoxide, isomenthoxide, fenchoxide, and borneoxide) in dimethylformamide at 80{degree}C for 30 min. Compound 2 was found to undergo facile halogen-metal exchange with n-BuLi in THF at {minus}78{degree}C to afford the 2-lithio-6-alkoxypyridines (3). Treatment of 3 with R{sub 2}SiCl{sub 2} resulted in formation of the novel bis(pyridyl)silane compounds (2-(6-alkoxypyridyl)){sub 2}SiR{sub 2} (4, R = Me; 5, R = Ph) in excellent yield. The latter compounds readily chelated to palladium(II) chloride to form air-stable complexes, {l brace}(2-(6-alkoxypyridyl)){sub 2}SiR{sub 2}{r brace}PdCl{sub 2} (6, R = Me; 7, R = Ph). The palladium complexes were fully characterized by spectroscopic and analytical data. Oxidative coupling of compounds 3 with copper(I) iodide and oxygen at {minus}78{degree}C afforded the new 6,6{prime}-dialkoxy-2,2{prime}-bipyridines (8) in 34-38% isolated yields. Treatment of 3 with dimethylformamide produced a new series of optically pure 6-alkoxy-2-pyridinecarboxaldehydes (9) in greater than 90% isolated yield. Subsequent reaction of 9 with 3 afforded the bis(2-(6-alkoxypyridyl))methanol ligands (10) in excellent yield. Compound 10 was O-alkylated (NaH, DMF) with benzyl chloride to afford 11. The benzylated compound 11 was complexed to palladium(II) chloride and found by NMR spectroscopy to exist as one of the two possible boat conformations. The energy barriers for rotation about the benzyl-oxygen bond in the latter complexes were found to be dependent upon the chiral alkoxy group on the pyridine ring. Ligand 10 was attached to cross-linked polystyrene beads with 56-74% modification of the chloromethyl sites.

• OSTI ID: 6654680
• Journal Information: Organometallics; (USA), Journal Name: Organometallics; (USA) Vol. 9:1; ISSN 0276-7333; ISSN ORGND
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400200* -- Inorganic
Organic
& Physical Chemistry
ALCOHOLS
ALKANES
CATALYSIS
COMPLEXES
DATA
DATA ANALYSIS
EXPERIMENTAL DATA
HYDRIDES
HYDROCARBONS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
INFORMATION
LIGANDS
MEASURING INSTRUMENTS
MEASURING METHODS
METHANOL
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC SILICON COMPOUNDS
PROPANE
RHODIUM COMPLEXES
SILANES
SILICON COMPOUNDS
SYNTHESIS
TRANSITION ELEMENT COMPLEXES