Titanium complexes containing a bridging indenylethylamido ligand have been synthesized and used as catalysts for hydroamination and hydroaminoalkylation reactions. All dichloro titanium complexes (η 5 :η 1 -Ind-C 2 H 4 -NR)TiCl 2 (R = i-Pr (2a), t-Bu (2b), Cy (2c), Ph (2d)), which were prepared by reacting TiCl 4 (Et 2 O) 2 with Li 2 [Ind-C 2 H 4 -NR], were fully characterized by single-crystal X-ray analysis. Reaction of 2a−c with methyllithium gave the thermally sensitive corresponding dimethyl titanium complexes [η 5 :η 1 -Ind-C 2 H 4 -N(alkyl)]TiMe 2 (alkyl = i-Pr (3a), t-Bu (3b), Cy (3c)), while the N-aryl-substituted dimethyl titanium complexes [η 5 :η 1 -Ind-C 2 H 4 -N(aryl)]-TiMe 2 (aryl = Ph (3d), p-MeOC 6 H 4 (3e)) were directly prepared by reacting Li 2 [Ind-C 2 H 4 -N(aryl)] with in situ generated Cl 2 TiMe 2 . In the case of complex 3d, the molecular structure could be determined by single-crystal X-ray analysis. All dimethyl titanium complexes (η 5 :η 1 -Ind-C 2 H 4 -NR)TiMe 2 (R = i-Pr (3a), t-Bu (3b), Cy (3c), Ph (3d), p-MeOC 6 H 4 (3e)) were finally used as precatalysts for the intermolecular hydroaminoalkylation of 1-octene (4), the intramolecular hydroamination and hydroaminoalkylation reactions of aminoalkenes, and the intermolecular hydroamination of 1-phenylpropyne (12). These experiments showed that the N substituent of the indenylethylamido ligand strongly influences the activity of the catalysts in the individual reactions.
Dedicated to Professor Jürgen Martens in honor of his outstanding contribution to synthetic organic chemistry DOI: http://dx.doi.org/10.3998/ark.5550190.p008.859
AbstractVarious indenylethylamines are synthesized for the first time by reductive amination of 2-(1H-inden-1-yl)acetaldehyde with commercially available primary amines. In addition, a new twostep synthesis of 2-(1H-inden-1-yl)acetaldehyde that uses inexpensive indene and 2-bromo-1,1-diethoxyethane as starting materials is presented. Finally, a selected indenylethylamine is used as a ligand precursor for the synthesis of a corresponding indenylethylamido titanium complex. The latter result paves the way for applications of corresponding complexes as catalysts for important chemical reactions.
New two‐step procedures that include an initial regioselective intermolecular hydroaminoalkylation of 2‐allyl‐, 2‐allyldimethylsilyl‐, or 2‐dimethyl(vinyl)silyl‐substituted 3‐bromothiophenes or 3‐bromobenzothiophenes with secondary amines and a subsequent intramolecular Buchwald‐Hartwig amination give direct access to structurally novel bicyclic heterocycles including tetrahydrothienopyridines, tetrahydrothienoazasilines, tetrahydrobenzothienoazasilines, and tetrahydrobenzothienoazasilepines. The hydroaminoalkylation reaction is catalyzed by a mono(aminopyridinato) titanium complex which delivers the branched hydroaminoalkylation products or in the case of vinylsilyl‐substituted substrates, the use of a bis(aminopyridinato) titanium complex gives access to the linear regioisomers. While in the latter case, the hydroaminoalkylation products need to be purified prior to the palladium‐catalyzed amination step, all other two‐step sequences can be run as a one‐pot procedure.
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