Imidotitanium complex

Reactions of the cyclopentadienyl-amidinate-supported imidotitanium complexes with CO2 proceed via initial cycloaddition reactions, but depending on the imido Af-substituent go on to yield products of either isocyanate extrusion or unprecedented double CO2 insertion (Scheme 89). ... 

Solution-phase approaches have been successfully adopted by a number of other groups in order to both discover and optimize olefin polymerization catalysts. Mason and Coates used GPC on polymer mixtures from pooled catalyst libraries in order to identify active heteroligated phenoxyimine titanium catalysts. Hinderling and Chen reported electrospray ionization tandem mass spectrometry (ESI-MS/MS) as a means of identilying palladium catalyst complexes in pooled libraries. Adams a al. analyzed a library of 50 imidotitanium complexes for ethylene polymerization, and identified seven active complexes. Finally, in a study by Jones et a library of 205... 

Schafer found that the bulky bis(amidate) complex is an effective catalyst for intermolecular hydroamination of terminal alkyl alkynes with alkylamines, giving exclusively the anti-Markovnikov aldimine product [309]. The same titanium complexes can also be utilized in the hydroamination of substituted allenes in good yields (Scheme 14.132). Under the catalysis of an imidotitanium complex, the highly strained methylenecyclopropane can undergo hydroamination reaction with either aromatic or aliphatic amines, to give ring-opened imine products in good to excellent yields and chemoselectivities [310]. 

M06/6-31-l-l-G calculations in the gas phase and using the CPCM (conductor-like polarizable continuum model) in solution have shown that the formal reaction of imidozirconocene with allylic ethers and an imidotitanium complex with allylic alcohols occurs by a [2 -I- 2] cycloaddition/retro- [2 -I- 2] pathway via central transition states rather than by the proposed [3,3] sigmatropic rearrangement mechanism. ... 

Based on the established mechanism for titanium-catalyzed hydroamination, the authors propose a reversible reaction between a titanium imide complex and the alkyne to form metalloazacyclobutene 86, which in turn undergoes 1,1-insertion of the isonitrile into the Ti-C bond. The generated five-membered ring iminoacyl-amido complex 87 with the new C-C bond is protonated by the primary amine to afford the desired three-component coupling product, with regeneration of the catalytic imidotitanium species. Very recently, titanium-catalyzed carbon-carbon bond-forming reactions have been reviewed.122... 

The imidotitanium and titanocene complexes have been used as the chiral catalysts in the hydroamination/hydrosilylation sequences of alkynylamines in one pot to yield the cyclic amines with up to 66% ee (Scheme 14.140). Although the results have not yet been satisfactory, this sequential reaction opens up the field for using other ligands and substrates [303]. 

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