The first examples of titanium‐catalyzed hydroaminoalkylation reactions of ethylene with secondary amines are presented. The reactions can be achieved with various titanium catalysts and they do not require the use of high pressure equipment. In addition, the first solid‐state structure of a titanapyrrolidine that is formed by insertion of an alkene into the Ti−C bond of a titanaaziridine is reported.

The first cationic titanium catalyst system for the intermolecular hydroaminoalkylation of alkenes with various tertiary alkylamines is presented. Corresponding reactions which involve the addition of the a-CÀH bond of a tertiary amine across the CÀC double bond of an alkene take place at temperatures close to room temperature with excellent regioselectivity to deliver the branched products exclusively. Interestingly, for selected amines, a-C À H bond activation occurs not only at N-methyl but also at N-methylene groups.Tertiary amines are important structural motifs in natural products (e.g. alkaloids) and are indispensable for the development of agrochemicals or pharmaceuticals. [1] For example, more than 15 % of the 200 top selling small molecule drugs in 2018 contain a tertiary amine moiety. [1b] An attractive synthetic approach for the synthesis of various amines that has raised a lot of attention in recent years is the hydroaminoalkylation of alkenes which allows the 100 % atom economic addition of the a-C À H bond of simple amines across the C À C double bond of alkenes (Scheme 1). [2] Corresponding addition reactions can be achieved with late transition metal catalysts, [3] following a photo-catalytic approach, [4] or most efficiently with early transition metal catalysts. [5][6][7] In the latter case, neutral group 4 [5] and 5 [6] metal catalysts have extensively been used for a plethora of successful hydroaminoalkylation reactions of alkenes with primary or secondary amines (Scheme 1 a) but unfortunately, tertiary amines do not react successfully with alkenes in the presence of these catalysts. This lack of reactivity must be regarded as a severe restriction to the use of hydroaminoalkylation reactions, because it prohibits the use of simple tertiary amines as starting materials for the synthesis of more sophisticated tertiary amine products. Although a few late transition metal-catalyzed hydroaminoalkylation reactions with tertiary amines have been reported, [3,4] in these cases, the amine must contain an additional metal-binding directing

The first cationic titanium catalyst system for the intermolecular hydroaminoalkylation of alkenes with various tertiary alkylamines is presented. Corresponding reactions which involve the addition of the a-CÀH bond of a tertiary amine across the CÀC double bond of an alkene take place at temperatures close to room temperature with excellent regioselectivity to deliver the branched products exclusively. Interestingly, for selected amines, a-C À H bond activation occurs not only at N-methyl but also at N-methylene groups.

Vinylsilanes undergo intermolecular alkene hydroaminoalkylation with secondary amines in the presence of a titanium mono(aminopyridinato) catalyst to give the branched hydroaminoalkylation products with high regioselectivity. Corresponding reactions of a suitable (2-bromophenyl)vinylsilane combined with a subsequent intramolecular Buchwald–Hartwig amination result in the development of an elegant one-pot procedure for the synthesis of 1,4-benzoazasilines.

Industrially important ethylene easily inserts into the titanium carbon bond of titanaaziridines to give titanapyrrolidines. Based on this reaction, this work reports the first examples of titanium‐catalyzed hydroaminoalkylation reactions of ethylene with secondary amines, which directly deliver α‐ethylated amines. The picture, created by Iris Töben, shows a simplified catalytic cycle in front of Oldenburg Palace, which is located in the city center of Oldenburg where the researchers developed the new reaction. More information can be found in the Communication by R. Beckhaus, S. Doye, et al. on page 2138.