Cyclopropanation bipyridine ligands

It is also interesting to point out that bipyridine RZnCHiX complexes are not reactive in the cyclopropanation reaction due to the high basicity of the bipyridine ligand. However, the addition of zinc iodide promotes the cyclopropanation reaction since uncomplexed IZnCH2X can be formed via an iodide-halomethyl group exchange. This approach has been used in catalytic asymmetric cyclopropanation reactions vide infra). 

Several chiral 2,2 -bipyridine ligands when reacted with [Mo(CO)6] give complexes 18, 19 (R = H, Me), and 20 usable as catalysts in asymmetric allylic substitution, allylic oxidation, and cyclopropanation (01OM673). 

Chiral bipyridine ligands have been explored for the asymmetric cyclopropanation of diazoacetate. For example, Lyle and Wilson reported that optically active C2-symmetric 2,2 -bipiridyl 248 served as a good ligand for asymmetric cyclopropanation in the presence of CuOTf and phenyl hydrazine (Scheme 1.116) [173]. Boyd et al. showed that a similar 2,2 -bipyridyl 249 also worked as an effective catalyst (Scheme 1.117) [174]. Mono-oxazoline-substituted 2,2 -bipyridyl derivatives 250-252 have been examined (Scheme 1.118) [175]. Chiral double helical oligopyridine... 

Pyridine-based N-containing ligands have been tested in order to extend the scope of the copper-catalyzed cyclopropanation reaction of olefins. Chelucci et al. [33] have carefully examined and reviewed [34] the efficiency of a number of chiral pyridine derivatives as bidentate Hgands (mainly 2,2 -bipyridines, 2,2 6, 2 -terpyridines, phenanthrolines and aminopyridine) in the copper-catalyzed cyclopropanation of styrene by ethyl diazoacetate. The corresponding copper complexes proved to be only moderately active and enantios-elective (ee up to 32% for a C2-symmetric bipyridine). The same authors prepared other chiral ligands with nitrogen donors such as 2,2 -bipyridines 21, 5,6-dihydro-1,10-phenanthrolines 22, and 1,10-phenanthrolines 23 (see Scheme 14) [35]. 

Ito and Katsuki (55) examined the use of chiral bipyridine (bpy) compounds as ligands in the asymmetric cyclopropanation of alkenes. Moderate diastereoselectivities and excellent enantioselectivities were observed in the cyclopropanation of vinyl arenes, Eq. 38. This catalyst system afforded very high ee values of the cis isomer. 

Asymmetric cyclopropanations of alkenes and alkynes with a-diazocarbonyl compounds have been extensively explored in recent years and a number of very effective chiral catalysts have been developed2. Copper complexes modified with such chiral ligands as salicy-laldimines 38202,203, semicorrins 39204 208, bis(oxazolines) 40209-2" and bipyridines 41212 have... 

A novel soluble complex, (t/ -ethene)hydrotris(3,5-dimethylpyrazol-l-yl)boratocopper(I) (3) mediates the cyclopropanation of styrene, hex-1 -ene, and cyclooctene with ethyl diazoacetate in 76 96% yield (25 C, 1 mol% of catalyst).Copper complexes with the tridentate 2,6-bis[(5-oxo-2,5-dihydropyrrol-2-ylidene)methyl]pyridine ligand or homologous tetradentate l,T-bipyridine and l,T-biisoquinoline ligands are also suited to cyclopropanation of styrene with ethyl diazoacetate. 

Synthesis of neutral Ji-allylpalladium complexes having bisnitrogen ligands (mainly, those related to 2-(pyrazol-3-yl)pyridine, 2-(imidazol-2-yl)pyridine, and 2,2-bipyridine) and palladium-catalyzed cyclopropanation of ketene silyl acetals with allylic acetates 00YGK736. 

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