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Redox-responsive catalysis: fine tuning of chemoselectivity in the intramolecular reaction of diazo compounds catalysed by ferrocene-functionalised dirhodium() complexes
A series of heteroleptic dirhodium( ii ) complexes ( 1a-k ) of formula [Rh 2 (OAc) 3 (L)], where L is a redox-active ferrocenecarboxylate ligand, have been evaluated in the redox-responsive, dirhodium( ii )-catalysed decomposition of several diazo substrates prone to chemoselectivity issues. The inf...
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Published in: | New journal of chemistry 2023-05, Vol.47 (2), p.961-961 |
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Main Authors: | , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites |
Online Access: | Get full text |
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Summary: | A series of heteroleptic dirhodium(
ii
) complexes (
1a-k
) of formula [Rh
2
(OAc)
3
(L)], where L is a redox-active ferrocenecarboxylate ligand, have been evaluated in the redox-responsive, dirhodium(
ii
)-catalysed decomposition of several diazo substrates prone to chemoselectivity issues. The influence of the counter-anion of chemically oxidised ferrocenyl-containing complexes on the chemoselectivity of the decomposition of the diazo compound
2
has been investigated with complexes
1a-d
: bulky, weakly coordinating SbF
6
−
and BAr
F
4
−
([(3,5-(CF
3
)
2
C
6
H
3
)
4
B]
−
) result in a greater chemoselectivity difference between the reduced and oxidised versions of the catalyst than BF
4
−
. The correlation between the electronic nature of the ferrocenyl substituents and the extent of the chemoselectivity switch is not obvious, as complex
1a
with unsubstituted ferrocene gave the best results upon oxidation among complexes
1a-k
. The introduction of a saturated tether in
1j-k
drastically decreases the chemoselectivity difference between the reduced and oxidised species. Finally, two additional diazo compounds with various chemoselectivity issues (
9
and
10
) were evaluated in the presence of complexes
1a
and
1a
+
·SbF
6
−
: the decomposition of diazo complex
9
, producing an aromatic C-H insertion product
11
and a cyclopropanation product
12
, led to a 42% chemoselectivity difference between
1a
and
1a
+
·SbF
6
−
. This demonstrates that changing the electronic properties of only one ligand on dirhodium, by oxidation of its ferrocenyl part, can have a marked influence on the reaction selectivity.
In redox-responsive carbene transfer catalysis using neutral or oxidised forms of ferrocene-containing dirhodium(
ii
) species, the weakly interacting SbF
6
−
anion allows a greater chemoselectivity change toward the aromatic C-H insertion product than BF
4
−
. |
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ISSN: | 1144-0546 1369-9261 |
DOI: | 10.1039/d3nj01131c |