Efficient N-alkyl enamination of 3-(thiobenzoyl)pyrrolo[2,3-b]quinoxalin-2-one, E/Z isomerisation of the reaction products and potential fluorescent sensors for zinc(II)ion
Efficient N-alkyl enamination of 3-(thiobenzoyl)pyrrolo[2,3-b]quinoxalin-2-one, E/Z isomerisation of the reaction products and potential fluorescent sensors for zinc(II)ion
Efficient N-alkyl enamination of 3-(thiobenzoyl)pyrrolo[2,3-b]quinoxalin-2-one, E/Z isomerisation of the reaction products and potential fluorescent sensors for zinc(II)ion
author:
Ostrowska Katarzyna , Piegza Edyta, Rąpała-Kozik Maria , Stadnicka Katarzyna
An efficient and rapid procedure for the
N
-alkyl enamination
from thioketones to push–pull (
E
/
Z
)-enamine derivatives is
reported. The starting thioketone
2
was obtained by regiose-
lective thionation of 3-benzoylpyrrolo[2,3-
b
]quinoxalin-2-
one (
1
) with Lawesson’s reagent (LR).
1
H NMR and X-ray
crystal structure analyses of 1-aryl-3-(alkylaminophenyl-
methylidene)pyrrolo[2,3-
b
]quinoxalin-2-ones
3
–
6
confirmed
that the
E
diastereoisomers predominated. Interconversion of the isolated
E
form of
3b
and
4a
into the
Z
configuration and
their
E
/
Z
equilibria in [D
6
]DMSO were studied by tempera-
ture-dependent
1
H NMR spectroscopy. The photophysical
properties of compounds
1
–
6
are also reported. We found that
the non-fluorescent compounds
3a
–
6a
are chemosensors for
the zinc ion. Fluorescent titrations of these sensors with zinc-
(II) acetate showed that compound
6a
has the best working
range of zinc concentrations with
K
d
= 3.77 00
0.51
μ
M.
keywords in English:
nitrogen heterocycles, zinc, enamines, E / Z interconversion, fluorescent probes
departmental parameterization:
30
affiliation:
Wydział Chemii : Zakład Krystalochemii i Krystalofizyki, Wydział Biochemii, Biofizyki i Biotechnologii : Zakład Biochemii Analitycznej, Wydział Chemii : Zakład Chemii Organicznej