5 research outputs found
Divergent Cyclizations of 1‑R-Ethynyl-9,10-anthraquinones: Use of Thiourea as a “S<sup>2–</sup>” Equivalent in an “Anchor-Relay” Addition Mediated by Formal C–H Activation
The EtONa-mediated reaction of <i>peri</i>-R-ethynyl-9,10-anthraquinones
with thiourea yields 2-R-7<i>H</i>-dibenzo[<i>de</i>,<i>h</i>]quinolin-7-ones and 2-R-anthra[2,1-<i>b</i>]thiophene-6,11-diones. Although 2-R-7<i>H</i>-dibenzo[<i>de</i>,<i>h</i>]quinolin-7-ones were observed previously
in reactions with other N-centered nucleophiles (hydrazine, guanidine,
and urea), the formation of 2-R-anthra[2,1-<i>b</i>]thiophene-6,11-diones
is a new reactivity path. DFT computations analyzed factors responsible
for the switch in reactivity and the relative importance of two possible
pathways: (1) the “anchor-relay” mechanism mediated
by nucleophilic attack at the carbonyl and (2) direct attack at the
alkyne. The two pathways converge on a vinyl sulfur anion, set up
for a 5-endo-trig cyclization at the <i>ortho</i>-position.
Subsequent rearomatization/oxidation provides the fused thiophene
product via formal C–H activation. The calculations suggest
that the latter pathway, the direct attack at the alkyne, is more
likely, due to the relatively high barrier for the 8-endo-dig cyclization
(pathway 1). Computational insights led to a more selective synthesis
of fused thiophenes, based on the reaction of acetylenic anthraquinones
with sodium sulfide. This reaction does not require prefunctionalization
at the <i>ortho</i>-position since direct C–H activation
is efficient. The absence of fused five-membered heterocycles in earlier
work was investigated computationally. The other N-centered nucleophiles
form stronger anion−π complexes with the electron-deficient
quinone core, promoting carbonyl attack over direct alkyne attack
Conformational Flexibility of Fused Tetracenedione Propellers Obtained from One-Pot Reductive Dimerization of Acetylenic Quinones
Reductive
dimerization of acetylenic anthraquinones provides synthetic
access to flexible nonplanar polyaromatics with a tetracenedione core.
In solution, these nonplanar, contorted polycycles exist as equilibrating
mixtures of two symmetric conformers. The fused tetracenediones are
easily reduced and exhibit rich electrochemical behavior
Conformational Flexibility of Fused Tetracenedione Propellers Obtained from One-Pot Reductive Dimerization of Acetylenic Quinones
Reductive
dimerization of acetylenic anthraquinones provides synthetic
access to flexible nonplanar polyaromatics with a tetracenedione core.
In solution, these nonplanar, contorted polycycles exist as equilibrating
mixtures of two symmetric conformers. The fused tetracenediones are
easily reduced and exhibit rich electrochemical behavior
X‑ray Generated Recombination Exciplexes of Substituted Diphenylacetylenes with Tertiary Amines: A Versatile Experimental Vehicle for Targeted Creation of Deep-Blue Electroluminescent Systems
Customizable
and technology-friendly functional materials are one
of the mainstays of emerging organic electronics and optoelectronics.
We show that recombination exciplexes of simple substituted diphenylacetylenes
with tertiary amines can be a convenient source of tunable deep-blue
emission with possible applications in organic electroluminescent
systems. The optically inaccessible exciplexes were produced via recombination
of radiation-generated radical ion pairs in alkane solution, which
mimics charge transport and recombination in the active layer of practical
organic light-emitting diodes in a simple solution-based experiment.
Despite varying and rather poor intrinsic emission properties, diphenylacetylene
and its prototypical methoxy (donor) or trifluoromethyl (acceptor)
monosubstituted derivatives readily form recombination exciplexes
with <i>N</i>,<i>N</i>-dimethylaniline and other
tertiary amines that produce emission with maxima ranging from 385
to 435 nm. The position of emission band maximum linearly correlates
with readily calculated gas-phase electron affinity of the corresponding
diphenylacetylene, which can be used for fast computational prescreening
of the candidate molecules, and various substituted diphenylacetylenes
can be synthesized via relatively simple and universal cross-coupling
reactions of Sonogashira and Castro. Together, the simple solution-based
experiment, computationally cheap prescreening method, and universal
synthetic strategy may open a very broad and chemically convenient
class of compounds to obtain OLEDs and OLED-based multifunctional
devices with tunable emission spectrum and high conversion efficiency
that has yet not been seriously considered for these purposes
X‑ray Generated Recombination Exciplexes of Substituted Diphenylacetylenes with Tertiary Amines: A Versatile Experimental Vehicle for Targeted Creation of Deep-Blue Electroluminescent Systems
Customizable
and technology-friendly functional materials are one
of the mainstays of emerging organic electronics and optoelectronics.
We show that recombination exciplexes of simple substituted diphenylacetylenes
with tertiary amines can be a convenient source of tunable deep-blue
emission with possible applications in organic electroluminescent
systems. The optically inaccessible exciplexes were produced via recombination
of radiation-generated radical ion pairs in alkane solution, which
mimics charge transport and recombination in the active layer of practical
organic light-emitting diodes in a simple solution-based experiment.
Despite varying and rather poor intrinsic emission properties, diphenylacetylene
and its prototypical methoxy (donor) or trifluoromethyl (acceptor)
monosubstituted derivatives readily form recombination exciplexes
with <i>N</i>,<i>N</i>-dimethylaniline and other
tertiary amines that produce emission with maxima ranging from 385
to 435 nm. The position of emission band maximum linearly correlates
with readily calculated gas-phase electron affinity of the corresponding
diphenylacetylene, which can be used for fast computational prescreening
of the candidate molecules, and various substituted diphenylacetylenes
can be synthesized via relatively simple and universal cross-coupling
reactions of Sonogashira and Castro. Together, the simple solution-based
experiment, computationally cheap prescreening method, and universal
synthetic strategy may open a very broad and chemically convenient
class of compounds to obtain OLEDs and OLED-based multifunctional
devices with tunable emission spectrum and high conversion efficiency
that has yet not been seriously considered for these purposes