The Mechanism of the Titanium‐Catalyzed Hydroaminoalkylation of Alkenes

Abstract

Kinetic studies on the intramolecular titanium‐catalyzed hydroaminoalkylation of alkenes (see scheme) are consistent with theoretical results and lead to the conclusion that the rate‐determining step of the catalytic cycle is the CH activation at the α position to the nitrogen atom. The reaction has a high activation energy and involves a moderately ordered transition state.

Imines in the Titanium Coordination Sphere: Highly Reactive Titanaaziridines and Larger Titanacycles Formed by Subsequent C–C Coupling Reactions

“…[10] In particular, titanaaziridines have become important as the key intermediates in the hydroaminoalkylation of olefins. [1,12,13] To obtain a further understanding of those complexes that are often involved as catalysts [14,15] or intermediates [16][17][18][19][20][21][22][23] in organic synthesis, we investigated the synthesis and the structure as well as the reactivity of titanoceneaziridines depending on the substitution pattern of the imine used for the reductive complexation. In addition, we were interested in the manner in which the titanium(IV) precursor influences the reductive complexation of imines.…”

Highly flexible synthesis of indenylethylamines as ligand precursors for titanium complexes

“…After separation from the formed lithium chloride, red-brown crystals of the expected new titanium complex 16 could be isolated in 33 % yield. Subsequently, the obtained solid material could be recrystallized from benzene-d 6 to give red crystals that were suitable for X-ray single-crystal analysis. The solid-state structure of 16 ( Figure 1) 19 reveals a slightly distorted tetrahedral geometry around the titanium center and proves the bidentate binding mode of the new indenylethylamido ligand.…”

“…DMSO was distilled from CaH 2 and stored under an argon atmosphere over molecular sieves (4 Å) prior to use. Diethyl ether, toluene and benzene-d 6 were dried by distillation from sodium. Light petroleum ether (PE) and tert-butyl methyl ether (MTBE) for flash chromatography were purified by distillation.…”

“…Among the various titanium-catalysts, bis(η 5 -indenyl)dimethyltitanium (Ind 2 TiMe 2 ) 12 was found to be an excellent catalyst for the highly regioselective hydroaminoalkylation of 1-alkenes with N-methylanilines (Scheme 1). 5 In addition, the catalyst can be used for corresponding reactions of styrenes 5 5 The reaction mechanism of the titanium-catalyzed hydroaminoalkylation of alkenes has already been studied in detail 6 and it is generally accepted that titanaaziridines are the catalytically active species. These highly strained intermediates are formed under the reaction conditions from a catalyst precursor and the amine substrate.…”

Crystal structure of 1,1-bis(η 5-adamantylcyclopentadienyl)-3-phenyl-2-trimethylsilyl-2,3-dihydroisotitanazole, C42H55NSiTi

“…In this context, the hydroaminoalkylation of alkenes, in which the insertion of the alkene into the Ti-C bond of the titanaaziridine is supposed to be the C-C forming step [7][8][9][10], is likely the most important one. To the best of our knowledge, reactions of titanaaziridines and alkynes in the catalytic hydroaminoalkylation have not been reported until now.…”