Stoichiometric applications of organotransition metal complexes in organic synthesis

1,n-Dicarbanionic Titanium Intermediates from Monocarbanionic Organometallics and Their Application in Organic Synthesis

“…The electron density of a metal−carbon bond in any organometallic compound is shifted to the more electronegative carbon atom, and the majority of synthetically useful transformations of these reagents, including carbon−carbon bond forming reactions, in a formal sense correspond to a recombination of the corresponding monocarbanionic equivalent R - of an organometallic reagent R δ- M δ+ with an electrophilic substrate (Scheme , eq 1). These reactions may sometimes dramatically change their rates or even modes when conducted in the presence of a transition-metal compound. − Thus, their use sometimes allows one not only to modify the reactivity of nontransition organometallics, but also to perform new kinds of transformations due to a structural reorganization of the carbanionic moiety. These transformations may be formally expressed by eq 2 in Scheme , where R - and R *- are structurally different carbanionic equivalents of the same starting organometallic reagent R δ- M δ+ .…”

“…These reactions may sometimes dramatically change their rates or even modes when conducted in the presence of a transition-metal compound. [3][4][5][6][7][8][9][10] Thus, their use sometimes allows one not only to modify the reactivity of nontransition organometallics, but also to perform new kinds of transformations due to a structural reorganization of the carbanionic moiety. These transformations may be formally expressed by eq 2 in Scheme 1, where Rand R *are structurally different carbanionic equivalents of the same starting organometallic reagent R δ-M δ+ .…”

Scope and mechanism of the highly stereoselective metal-mediated domino aldol reactions of enolates with aldehydes

“…Metal enolates (Ti [ 23 ], Zr [ 24 ], Si [ 25 ], and Sn [ 26 ]) and boron enolates [ 27 ] have adopted a considerable significance because of their high potential to control the stereochemical outcome of the bond formation [ 28 – 30 ]. However, the other group III metal enolates have been almost completely omitted over the years [ 31 ].…”

Titanium-mediated syntheses of cyclopropylamines

“…The majority of synthetically useful transformations of these reagents, including carbon-carbon bond forming reactions, may sometimes dramatically change their rates or even modes when conducted in the presence of a transition-metal compound [2][3][4][5][6][7][8][9]. The use of the latter, especially of group(IV) transition-metal derivatives, sometimes not only allows one to modify the reactivity of non-transition organometallics, but also to perform new kinds of transformations due to a structural reorganization of the carbanionic moiety.…”