3,4‐Dihydro‐3 H ‐pyrrol‐2‐imines as Conformationally Restrained 1,3‐Diazabutadienes: Synthesis, Structural Properties and Protonation
Abstract 5‐Aryl‐3,3,4,4‐tetramethyl‐3,4‐dihydro‐3 H ‐pyrrol‐2‐imines,conformationally restrained 1,3‐diazabuta‐1,3‐diene derivatives, were easily prepared by treating aryllithium species with 2,2,3,3‐tetramethylsuccinonitrile ( 1 ). Trapping the reaction intermediate with chlorotrimethylsilane gave...
Saved in:
Published in | European journal of organic chemistry Vol. 2009; no. 13; pp. 2077 - 2087 |
---|---|
Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
01.05.2009
|
Online Access | Get full text |
Cover
Loading…
Summary: | Abstract
5‐Aryl‐3,3,4,4‐tetramethyl‐3,4‐dihydro‐3
H
‐pyrrol‐2‐imines,conformationally restrained 1,3‐diazabuta‐1,3‐diene derivatives, were easily prepared by treating aryllithium species with 2,2,3,3‐tetramethylsuccinonitrile (
1
). Trapping the reaction intermediate with chlorotrimethylsilane gave
N
‐silylated compounds
2a
–
e
, whereas aqueous workup gave N‐H derivatives
3a
,
b
. Pyrenyl‐substituted compound
3b
was characterised by X‐ray diffraction studies, revealing the presence of both intermolecular aromatic face‐to‐face contacts and the formation of homodimers by twofold H‐bonding.
N
‐Silylated derivatives
2a
–
d
were used successfully as nucleophilic components in palladium‐catalysed C–N bond‐forming reactions to obtain
N
‐arylated compounds
5b
–
h
,
j
,
k
,
m
and
7a
–
d
. The UV spectra of compounds
5
and
7
exhibit long wavelength absorptions up to 462 nm for
7d
, thus indicating extended π–π* conjugation. Dihydropyrrolimine‐based compounds with larger conjugated aryl substituents in the 5‐position react with Brønsted and Lewis acids displaying a significant colour change that could be used to estimate the p
K
b
of
3a
to a value of –4.5. Derivatives
2c
,
e
and
3a
,
b
, which are not
N
‐arylated, are fluorescent with a Stokes shift of 107 nm (6034 cm
–1
) for
3a
. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) |
---|---|
ISSN: | 1434-193X 1099-0690 |
DOI: | 10.1002/ejoc.200900045 |