A General Nickel-Catalyzed Hydroamination of 1,3-Dienes by Alkylamines:  Catalyst Selection, Scope, and Mechanism

Abstract

A simple colorimetric assay of various transition-metal catalysts showed that the combination of DPPF, Ni(COD)(2), and acid is a highly active catalyst system for the hydroamination of dienes by alkylamines to form allylic amines. The scope of the reaction is broad; various primary and secondary alkylamines react with 1,3-dienes in the presence of these catalysts. Detailed mechanistic studies revealed the individual steps involved in the catalytic process. These studies uncovered unexpected thermodynamics for the addition of amines to pi-allyl nickel complexes: instead of the thermodynamics favoring the reaction of a nickel allyl with an amine to form an allylic amine, the thermodynamics favored reaction of a nickel(0) complex with allylic amine in the presence of acid to form a Ni(II) allyl. The realization of these thermodynamics led us to the discovery that nickel and some palladium complexes in the presence or absence of acid catalyze the exchange of the amino groups of allylic amines with free amines. This exchange process was used to reveal the relative thermodynamic stabilities of various allylic amines. In addition, this exchange reaction leads to racemization of allylic amines. Therefore, the relative rate for C-N bond formation and cleavage influences the enantioselectivity of diene hydroaminations.

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

“…Halligudi 小组 [138] 则使用蒙脱石 K10 负载的锌离子催化了端基炔 [134] 报道了镍的配合物(Ni(triphos)) 2 (cod)催 化下 δ-胺基炔烃的定量分子内环化反应. Hartwig 小组 [149] 报道了对称的共轭二烯烃和一级胺或二级胺的分子间 加成反应. 一系列催化剂和配体的筛选表明, 双-(1,5-环 辛二烯)镍(Ni(COD) 2 )和 1,1'-双(二苯基膦)二茂铁体系催 化下反应的效率最高, 在室温下即可完成反应(Eq.…”

Primary tert‐ and sec‐Allylamines via Palladium‐Catalyzed Hydroamination and Allylic Substitution with Hydrazine and Hydroxylamine Derivatives

“…[3,4] During studies to develop the scope of the hydroamination of dienes, [5][6][7] we found that the reactions of hydrazine and hydroxylamine derivatives occur irreversibly at the more substituted position of both prenyl and crotyl palladium intermediates. We explored this transformation further because, unlike the products from additions of aziridines, [3,4] the products from addition of hydrazine and hydroxylamine derivatives could be readily transformed into primary tert-alkylamines or sec-alkylamines.…”

“…While studying the reactions of hydrazine derivatives with isoprene as an avenue to expand the scope of the hydroamination of dienes, [5][6][7] we found that these reactions formed the product in which the C-N bond is formed between the hydrazone group and the most substituted carbon atom of the diene. Table 1 shows these reactions catalyzed by palladium complexes containing a series of bidentate phosphine ligands.…”

Transition Metal‐Catalyzed Asymmetric Hydroamination of Alkenes (AHA)

“…[54] Rates could be increased by addition of TFA, but this was accompanied by a loss of stereoselectivity, because a fast exchange of the allylic amine in the presence of acids led to racemization of the hydroamination product. [59] Catalyst deactivation thwarted attempts to increase turnover frequencies by increasing the reaction temperature, resulting in lower overall conversions.…”