Broadening the Scope of Group 4 Hydroamination Catalysis Using a Tethered Ureate Ligand

Abstract

A broadly applicable group-4-based precatalyst for the hydroamination of primary and secondary amines was developed. Screening experiments involving a series of amide and urea proligands led to the discovery of a tethered bis(ureate) zirconium complex with unprecedented reactivity in the intermolecular hydroamination of alkynes and the intramolecular hydroamination of alkenes. This catalyst system is effective with primary and secondary amines, 1,2-disubstituted alkenes, and heteroatom-containing functional groups, including ethers, silanes, amines, and heteroaromatics. The gem-disubstituent effect is not required for cyclization. The catalyst is generally regioselective for the anti-Markovnikov product of intermolecular alkyne hydroamination, and chemoselective for hydroamination over alpha-alkylation when forming 6- and 7-membered rings from aminoalkenes.

Transition‐Metal‐Catalyzed Hydroamination Reactions

“…Indeed, the bulkier substrates that are less prone to such dimerization, such as tert-butylamine or cyclohexylamine (Table 15.2, entries 5-8, [13][14][15][16], show much improved yields using standardized reaction times. Interestingly, the Schafer group [34] has established that group 4 complexes can indeed be used for the intermolecular hydroamination of alkynes with secondary amines consistent with a shift in mechanism from the established [2+2] cycloaddition pathway. Specifically, a Zr ureate catalyst 5 has been developed to realize this shift in mechanism.…”

Iridium-Catalyzed, Intermolecular Hydroetherification of Unactivated Aliphatic Alkenes with Phenols

“…Sub- sequently, Schafer and co-workers proposed a similar transition state for the hydroamination of primary and secondary aminoalkenes catalyzed by zirconium complexes ligated by a tethered bis(ureate). [71] The proposed six-membered transition state accounts for the kinetic data obtained on the systems described by the groups of Sadow and Schafer and is a possible transition state for CÀN bond formation by the Ln and An systems described by the group of Marks. [53,[58][59][60] The orders in substrate, when combined with information on the resting state, and the KIE values suggest parallels between these systems.…”

Research Progress in Non-noble Metals Catalyzed Hydroamination of Alkyenes and Alkynes

“…以含有锆-氧键的尿素衍生物作为配体 的化合物 32(图 6)对于端基炔烃和二级胺的分子间反应 和形成五元或六元环的分子内环合都具有较好的底物 适用性 [95] . 研究者同时通过使用 1.0 equiv.的催化剂对…”