Titanaaziridines or η(2)-imine titanium complexes are considered key intermediates of the titanium-catalyzed hydroaminoalkylation of alkenes. Herein, we present an efficient synthetic route to this class of compounds, starting from N-methylanilines and a bis(η(5):η(1)-pentafulvene)titanium complex. Consecutive reactions on the η(2)-methyleneaniline complexes, characterized for the first time, prove a high chemical versatility. In particular, hydroaminoalkylation products were found in reactions of the three-membered titanacycles with alkenes. For the first time, all the intermediates of the hydroaminoalkylation of alkenes were isolated and characterized.

The C-C bond forming catalytic hydroaminoalkylation of terminal alkenes, 1,3-dienes, or styrenes allows a direct and highly atom efficient (100 %) synthesis of amines which can result in the formation of two regioisomers, the linear and the branched product. We present a new titanium catalyst with 2,6-bis(phenylamino)pyridinato ligands for intermolecular hydroaminoalkylation reactions of styrenes and 1-phenyl-1,3-butadienes that delivers the corresponding linear hydroaminoalkylation products with excellent regioselectivities.

An easily accessible formamidinate ligand-bearing titanium complex initially synthesized by Eisen et al. is used as catalyst for intermolecular hydroaminoalkylation reactions of unactivated, sterically demanding 1,1- and 1,2-disubstituted alkenes and styrenes with secondary amines. The corresponding reactions, which have never been achieved with titanium catalysts before, take place with excellent regioselectivity (up to 99 : 1) and in addition, corresponding reactions of 1,3-butadienes with N-methylbenzylamine are also described for the first time.

Dedicated to Professor Ekkehard Winterfeldt on the occasion of his 80th BirthdayThe hydroaminoalkylation of alkenes [1] is a highly atom efficient (100 %) reaction that allows the addition of the a-CÀ H bond of an amine across a CÀC double bond (Scheme 1).As the formed a-alkylated amines are of great industrial importance it is not surprising that a number of hydroaminoalkylation catalysts have already been identified. [2][3][4][5][6] Successful hydroaminoalkylation reactions of alkenes can be achieved in the presence of ruthenium, [2] iridium, [3] Group 5 metals, [4] zirconium, [5] or titanium catalysts [6] but the use of ruthenium and iridium catalysts is limited to amine substrates possessing a directing 2-pyridinyl substituent bound to the nitrogen atom of the amine. [2,3] While in the presence of Group 5 metal catalysts or [Ind 2 TiMe 2 ] (Ind = h 5 -indenyl), the hydroaminoalkylation of 1-alkenes, such as 1-octene (2), with secondary amines, such as N-methylaniline (1), always gives the branched product 3 a exclusively (Scheme 1), the corresponding [Ind 2 TiMe 2 ]-catalyzed reaction of styrene (4) also leads to the formation of the linear product 5 b as a side product. [6d] Unfortunately, successful [Ind 2 TiMe 2 ]-catalyzed hydroaminoalkylation reactions could only be achieved with N-methylanilines and in this context, it must also be mentioned that by using Group 5 metal catalysts only a single additional example of a successful hydroaminomethylation of a styrene has been reported. [4i] In this case, the branched product was again the exclusive product of the reaction. Interestingly, linear side products could also be obtained from hydroaminoalkylation reactions of 1-alkenes performed with [Ti(NMe 2 ) 4 ] [6b] or [TiBn 4 ] [6c] (Bn = benzyl) as the catalysts. However, to our knowledge, up to now, no early transition-metal-catalyzed hydroaminoalkylation of an alkene or a styrene that leads to the formation of the industrially important linear product as the major product of the reaction has been reported. [7] In addition, hydroaminoalkylation reactions of styrenes with dialkylamines or Nalkylanilines possessing alkyl groups larger than a methyl group have never been achieved.To expand the substrate scope of the hydroaminoalkylation of alkenes, we recently performed a number of corresponding transformations with N-methylated aminoheteroaromatics as substrates in the presence of the precatalyst [Ti(NMe 2 ) 4 ]. During these unsuccessful attempts we observed that the addition of 2-(methylamino)pyridine (2-MeAP-H) to a bright yellow solution of the alkene and the precatalyst [Ti(NMe 2 ) 4 ] in toluene results in a significant color change to dark red which suggests a fast formation of titanium complexes with 2-aminopyridinato ligands, [8] such as [(2-MeAP) 2 Ti(NMe 2 ) 2 ] or [(2-MeAP)Ti(NMe 2 ) 3 ] (Scheme 2). In this context, it must be noted that Kempe has already synthesized the complex [(2-MeAP) 2 Ti(NMe 2 ) 2 ] by amine Scheme 1. [Ind 2 TiMe 2 ]-catalyzed hydroaminoalkylation. [6d]Scheme 2. Detection ...

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