Intermolecular Hydroaminoalkylation of Alkynes.

Intermolecular hydroaminoalkylation reactions of alkynes with secondary amines, which selectively give access to allylic amines with E configuration of the alkene unit, are achieved in the presence of titanium catalysts. Successful reactions of symmetrically substituted diaryl- and dialkylalkynes as well as a terminal alkyne take place with N-benzylanilines, N-alkylanilines, and N-alkylbenzylamines.

Intermolecular Hydroaminoalkylation of Propadiene.

Intermolecular hydroaminoalkylation reactions of propadiene with selected secondary amines take place in the presence of a 2,6-bis(phenylamino)pyridinato titanium catalyst. The corresponding products, synthetically useful allylamines, are formed in convincing yields and with high selectivities. In addition, propadiene easily inserts into the titanium-carbon bond of a titanaaziridine.

Synthesis of a titanium ethylene complex via C-H-activation and alternative access to Cp2Ti(η2-Me3SiC2SiMe3).

The synthesis of the novel room temperature stable titanacyclopropane derivative Cp*Ti(η2-C2H4)(η5-C5H4AdH) (2) in a one-step-two-transformation protocol and first insights into its reactivity are presented, including the synthesis of the corresponding bis(trimethylsilyl)acetylene complex Cp*Ti(η2-Me3SiC2SiMe3)(η5-C5H4AdH) (4). Given these results, a novel one-pot procedure toward Cp2Ti(η2-Me3SiC2SiMe3) was subsequently developed.

Unexpected Selective Methyl Group Abstractions from SiMe3 Moieties of CH2 SiMe3 Ligands To Give New Cationic Titanium Complexes.

The synthesis of the alkylated pentafulvene titanium complex Cp*Ti(CH2 SiMe3 )(π-η5 :σ-η1 -C5 H4 =CR2 ) (CR2 =adamantylidene) is described. The coordination mode of the pentafulvene ligand in this complex allowed for the subsequent synthesis of a series of nitrile-insertion products. By reacting these neutral compounds with the strong Lewis acid B(C6 F5 )3 , unprecedented selective methyl-group abstractions from the SiMe3 moieties under formation of novel cationic titanium complexes with the corresponding MeB(C6 F5 )3 - anion are demonstrated. The proposed silylium ion intermediates of these reactions are directly stabilized by either the exocyclic carbon atom of the pentafulvene ligand or by the lone pairs of the nitrogen atoms of the chelating Cp,N-ligands. In addition, a titanium enamine complex and its reaction with B(C6 F5 )3 is reported, which results in the formation of a betaine.

FLP behaviour of cationic titanium complexes with tridentate Cp,O,N-ligands: highly efficient syntheses and activation reactions of C-X bonds (X = Cl, F).

The synthesis of cationic titanium complexes 4a,b with tridentate Cp,O,N-ligand frameworks, starting from the monopentafulvene complex Cp*Ti(Cl)(π-η5:σ-η1-C5H4CR2 (CR2 = adamantylidene) (1) and bidentate O,N-ligand precursors CH3C(O)CH2CH2NR2 (R = Et, CH2Ph) (L1a,b), in a high-yielding and efficient two-step synthetic pathway is described. The ß-aminoketones L1a,b were synthesized by a herein reported solvent- and catalyst-free reaction. The reaction pathway involves insertion reactions, subsequent methylations and final activations with B(C6F5)3. NMR investigations of the cationic titanium complex 4a in deuterated dichloromethane revealed an ongoing selective reaction under formation of the cationic complex 5a-d2, which is the result of C-Cl bond cleavage. In addition to selective C-Cl bond activation reactions, C(sp3)-F bonds were activated by 4a,b, pointing out the special tm-FLP nature of 4a,b.

Teaching c-phosphanylimines the titanaaziridine coordination mode.

The c-phosphanylimine L1 was employed for the synthesis of the novel titanaaziridine 1 with an intramolecular phosphine donor side following a reductive complexation route. This coordination mode is new for c-phosphanylimines and compound 1 is the first group 4 complex featuring a c-phosphanylimine ligand.

Dehydroaromatization of quinoxalines: one-step syntheses of trinuclear 1,6,7,12,13,18-hexaazatrinaphthylene titanium complexes.

We report the spontaneous coupling of N-heterocycles, initiated by C-H bond activation reactions. The reaction of quinoxalines and the titanocene acetylene complex Cp2Ti{eta2-C2(SiMe3)2}, as an excellent titanocene source, results in the formation of trinuclear 1,6,7,12,13,18-hexaazatrinaphthylene (HATN) titanium complexes. These HATN titanium complexes are thermally stable but sensitive to air and moisture. A three-fold dehydrogenative C-C coupling is proposed as the main step in the presented synthetic procedure. Particularly using commercial starting materials, an efficient route for the dehydrogenative coupling of N-heterocycles, leading to multidentate ligands, has been established.