Cyclopropanation bipyridine complex

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]. 

Kwong et al. (57) examined the use of bipyridines containing chiral carbinol stereocenters in the 2,9 positions. Interestingly, reduction of 84 with diazoester occurred at ambient temperature unlike every other catalyst reported to date. The resulting complex efficiently mediates the cyclopropanation of styrene. 

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). 

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... 

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). 

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. 

When (2,2 -bipyridine)(cycloocta-l,5-diene)nickel was used as the catalyst various isomeric (2,2 -bipyridyl)nickelaspirocycloalkanes 4 and 5a-c were isolated.As expected, treatment of the dispiro complex 4 with methyl acrylate or maleic anhydride released dispiro[2.1.2.1]oc-tane (1) whereas the complexes 5 with one cyclopropane ring opened gave mainly 5-methyl-enespiroheptane 2. The formation of the 4-methylene isomer (from 5c) has not been observed in the dimerization reaction with other nickel(O) complexes. A few more nickel(O) complexes with an ability to catalyze the oligomerization of methylenecyclopropane have been de-scribed. ... 

Chiral bipyridine-copper complexes have also been recommended as catalysts in cyclopropanations of styrene and E-substituted styrenes by diazoesters, but this process leads to mixtures of stereoisomers [966, 967], The same limitations occur with bomanethione-derived chiral complexes [968],... 

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. 

New advances of asymmetric cyclopropanation reactions using chiral metal catalysts including metal complexes with oxazoline, porphyrin, bipyridine, and terpyridine derivatives 07CJO438. 

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