Tetrahedron Letters
An unprecedented cobalt-catalyzed selective aroylation of primary
amines with aroyl peroxides
Qian Zhang a,b, Juanjuan Li a,b, Jiale Li b, Songdong Yuan a,b, Dong Li a,
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a Hubei Collaborative Innovation Center for High-efficiency Utilization of Solar Energy, Hubei University of Technology, Wuhan 430068, China
b School of Materials and Chemical Engineering, Hubei University of Technology, Wuhan 430068, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel and facile cobalt-catalyzed selective aroylation of primary amines with aroyl peroxides was
developed for the synthesis of aryl amides. It was unprecedented that CAN bond formation product
was selectively generated without the common NAO bond formation product. Aroyl peroxides act as
the sole aroylation reagent without additional base or oxidant. The reactions proceeded under mild con-
ditions and showed broad substrates scope with a series of primary amines and aroyl peroxides.
Ó 2020 Elsevier Ltd. All rights reserved.
Received 19 January 2020
Revised 1 August 2020
Accepted 20 August 2020
Available online 29 August 2020
Keywords:
Cobalt
Aroylation
Amine
Aroyl peroxide
Introduction
environmentally benign transition metal has exhibited unique
catalytic behavior in organic synthesis and attracted extensive
Amides are one of the most important functional groups as they
pervasively exist in biological molecules, natural products, phar-
maceuticals, and functional materials and are also extensively used
as versatile synthetic intermediates [1]. Acylation of simple amines
was a straightforward and powerful tool not only for preparation of
amides but also for protection of amines in multistep synthesis [2].
Traditional amide synthesis was accomplished through the reac-
tion between amines and acyl chlorides or acid anhydrides. The
condensation of amines and more general carboxylic acids in the
presence of stoichiometric activating reagents such as acyl chlo-
rides, azides, acid anhydrides, or carbodiimides were also widely
employed [3]. However these activating reagents are normally
expensive, unstable or toxic and the conditions are typically
detrimental to the compatibility of substrates. Recently, efforts
have also been devoted to transamidation reactions of amides or
esters [4].
Transition-metal-catalyzed acylation of amines emerged as a
facile and efficient methodology and has attracted much atten-
tion recently. Group (IV) metals such as Zr, Ti and noble metals
such as Ru, Rh, Pd, et al. have shown particularly catalytical effi-
ciency for the acylation of amines with carboxylic acids or car-
boxylic acid surrogates such as alcohols, aldehydes, ketones
and so on [5]. Cobalt as an inexpensive, earth-abundant and
attentions [6]. Nevertheless, the method employing cobalt cata-
lysts in amide synthesis are still rare and mainly limited to
use aldehydes as the acylation reagent in the presence of exter-
nal oxidant [7].
On the other hand, aroyl peroxides especially benzoyl peroxide
(BPO) was widely used as a strong oxidant or radical initiator in
organic synthesis. Recently, it was found to perform as a readily
available and useful arylcarboxy and aryl radical precursors for
efficient acyloxylation and arylation of carbonyl or aromatic com-
pounds [8,9]. Although aroylation side products were occasionally
formed in these reactions, BPO was rarely regarded as an aroyla-
tion reagent [10]. The reaction of amines with BPO was also stud-
ied, which commonly generated the (benzoyloxy)amines as the
major product along with minor benzamides (Scheme 1a) [11].
Actually these methods suffered from the competition of NAO
and CAN bond formation products especially in the case of primary
amines. Very recently, Yamamoto and coworkers developed an
efficient strategy for the selective NAO bond formation of amines
with BPO [12]. But no efforts has been devoted to the selective
CAN bond formation of amines using BPO as the sole benzoylation
reagent [13,14]. During our recent studies on cobalt catalysis, we
found an unprecedented cobalt-catalyzed selective benzoylation
of primary amines with BPO (Scheme 1b). In this reaction, CAN
bond formation product was selectively generated without the
common NAO bond formation product. A series of primary amines
and aroyl peroxides have been examined with this method for
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Corresponding author.
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