Titanium mediated reduction

Scheme 1. Generality of the titanium mediated reductive cyclopropanation of N,N-diakylcarboxamides. More than 60 compounds have been prepared by this route.

The following combinations have also been reported of titanium-mediated reductive coupling of imines TiCU-Mg in DME (or THF), TiCU-Li in DME (or THF), TiCU-EtjN in Catalytic use of... 

Cyanopyridines undergo titanium-mediated reductive cyclopropanation to give pyridylcyclopropylamines in good yield <20030L753>. Both 2- and 3-cyanopyridine react with the titanium species 81 formed from diethylzinc and methyltriisopropyloxytitanium in the presence of lithium isopropoxide to give the cyclopropylamine product in 80% and 82% yield, respectively (Equation 55). 

In addition to the above, two air-stable, crystalline 20-Tt-electron dithia-A, A -dihydroporphycene derivatives, specifically 3.51 and 3.52, have been prepared recently by Neidlein and coworkers (Scheme 3.1.8). As could perhaps be imagined, these species were also prepared via a low-valent titanium-mediated reductive coupling procedure, involving the diformyl thiophene-pyrrole 3.50, carried out in the presence of TiCU and Zn. Interestingly, it is not only 3.51 but also 3.52 that is isolated under these conditions. This stands in direct contrast to what is observed in the case of the mixed furan-pyrrole coupling discussed above (Scheme 3.1.7) there, only one of the two possible isomers was isolated. 

FIGURE 11.81 Solid-phase synthesis of dihydrobenzopyrans. (From Breitenbucher, J.G. and Hui, H.C., Titanium mediated reductive amination on sohd-support extending the utility of the 4-hydroxy-thiophenol linker, Tetrahedron Lett., 39, 8207, 1998.)... 

Scheme 10.154 Proposed reaction steps in the titanium-mediated reductive allene-alkene cross-coupling [125].

Moslin RM, Espino CG, Swager TM (2008) S)mthesis of conjugated pol3mers containing cis-phenylenevinylenes by titanium-mediated reductions. Macromolecules 42 452-454... 

Titanium-mediated reductive cross-coupling reactions between allylic alcohols and vinylsilanes have been reported to not only occur with high regio- and stereoselectivity, but also afford products complementary to those obtained from Claisen rearrangements. A reaction of the lithiated allylic alcohols 46 (R = PMB, C5H9,... 

A version of the titanium-mediated reductive coupling in which TiCL-Zn-Cu serves as the reductant is efficient in closing large-membered rings. The mechanism... 

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