Intermolecular Hydroaminoalkylation of Alkynes

Abstract

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.

Stereoselective Synthesis of Tertiary Allylic Amines by Titanium‐Catalyzed Hydroaminoalkylation of Alkynes with Tertiary Amines

“…Figure 1 proves that the two phenyl groups of E ‐ 3⋅HCl are cis to each other which means that the configuration of the trisubstituted double bond is E . In good agreement with mechanistic studies of the Sc‐catalyzed hydroaminoalkylation of alkenes with tertiary amines [10a–e] and the results of Zr‐ and Ti‐catalyzed hydroaminoalkylation reactions of alkynes with secondary amines, [5c,d] it is assumed that a cationic titanaaziridine acts as the catalytically active species of the new reaction (Scheme 3). The stereoselective formation of the trisubstituted double bond of the allylamine product can then easily be understood by a C−C bond forming insertion of the alkyne into the Ti−C bond of the cationic titanaaziridine, which selectively gives a 2‐titana‐3‐pyrroline in which the former alkyne substituents must be cis ‐oriented to each other [5c,d] …”

“…For that purpose, Ye used “double ligands” of a N‐heterocyclic carbene (IPr) and tricyclohexylphosphine, [5b] while Shi used a chiral phosphorus ligand which even allowed an enantioselective reaction [5a] . On the other hand, Schafer‘s group [5c] and ours [5d] have shown that alkyne hydroaminoalkylation also works with unprotected secondary amines in the presence of early transition metal catalysts based on Zr or Ti to obtain secondary allylic amines. Secondary amines as well as tertiary amines can also be used for hydroaminoalkylation reactions of alkenes and in the case of tertiary amines, a lot of progress has been achieved with late transition metal catalysts or using photocatalytic approaches [8,9] .…”

Tandem amide coupling and hydroamination: unexpected benzotriazole oxide addition to the propiolic acid triple bond

“…14 When working with alkynes, the complicating factor is the possibility of E and Z isomerism, but in some cases this can also be controlled through catalyst choice. 15 As part of our research on amino acid and amide derived nitrogen or phosphine ligands, we use their transition metal complexes as selective catalysts, 16,17 supramolecular building blocks 18,19 or anticancer agents. 20 In order to diversify the structures of our compounds, we wanted to synthesise a propiolic acid derivatized diamine C1 (Scheme 1(c)).…”

External-Ligand-Free, Nickel-Catalyzed Alkenylation of N-Sulfonylamines with Internal Alkynes

“…In 1989, Buchwald's group studied zirconocene-complexed imines, which were synthesized from lithium amides, and revealed a notably synthetic route to allylic amines through such intermediates. 8 Recently both the Schafer and Doye groups have reported elegant alkenylation reactions of amines with alkynes using a Zr catalyst 9 and a Ti catalyst, 10 respectively (Scheme 1a). Using a late transition metal, the Shibata group have reported carbonyl group-assisted, Ir-catalyzed -alkenylation of amides (Scheme 1b).…”