Mechanistic details of the cobalt-mediated dehydrogenative dimerization of aminoquinoline-directed benzamides
Key mechanistic features of the cobalt-mediated and aminoquinoline-directed dehydrogenative aryl-aryl coupling were investigated computationally and experimentally. A series of Co II and Co III complexes relevant to the proposed reaction cycle have been synthesized and characterized. Stoichiometric...
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Published in | Chemical science (Cambridge) Vol. 11; no. 23; pp. 685 - 696 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
CAMBRIDGE
Royal Soc Chemistry
21.06.2020
Royal Society of Chemistry |
Subjects | |
Online Access | Get full text |
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Summary: | Key mechanistic features of the cobalt-mediated and aminoquinoline-directed dehydrogenative aryl-aryl coupling were investigated computationally and experimentally. A series of Co
II
and Co
III
complexes relevant to the proposed reaction cycle have been synthesized and characterized. Stoichiometric reactions and electrochemical studies were used to probe the role of different additives in the reaction pathway. Computationally, three different mechanisms, such as
charge neutral
,
anionic
, and
dimetallic
were explored. It is shown that the mono-metallic
anionic
and
charge neutral
mechanisms are the most favorable ones, among which the former mechanism is slightly more encouraging and proceeds
via
the: (a) concerted-metalation-deprotonation (CMD) of the first benzamide C-H bond, (b) PivOH-to-PivO
−
rearrangement, (c) CMD of the second benzamide C-H bond, (d) C-C coupling, (e) product formation facilitated by the amide nitrogen re-protonation, and (f) catalyst regeneration. The rate-determining step of this multi-step process is the C-C coupling step. The computational studies suggest that the electronics of both the aryl-benzamide and pyridine fragments of the aminoquinoline-benzamide ligand control the efficiency of the reaction.
Anionic
mechanism is favorable, aryl-aryl C-C coupling is the rate-determining, a Co
II
and Co
III
aminoquinoline-directed benzamide complexes. |
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Bibliography: | CCDC 1862102 Electronic supplementary information (ESI) available: Computational details and the detailed crystallographic information for complexes 10.1039/d0sc02066d ) , 1 For ESI and crystallographic data in CIF or other electronic format see DOI 2 3 4 1848074 5 1988219 6 7 1862295 1-7 1850726 1848433 1862101 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 2041-6520 2041-6539 |
DOI: | 10.1039/d0sc02066d |