19 research outputs found
New fluorescent switches based on photochromic 2,3-diarylcyclopent-2-en-1-ones and 6-ethoxy-3-methyl-1H-phenalen-1-one
Pinacol rearrangement of cyclopent-3-en-1,2-diols: Cyclopentenone formation and interrupting reaction
Aerobic Dimerization of Ethyl 4‑Thienyl-3-ketobutanoate toward a Modifiable Photochromic Diarylethene Precursor
A unique chemical
transformation, the base-induced aerobic dimerization
of ethyl 4-(2,5-dimethylthiophen-3-yl)-3-ketobutanoate leading to
photochromic diarylethene with a 4-hydroxy-4-methylcyclopent-2-ene-1-one
as an ethene bridge, is described. This compound is easily subjected
to various chemical modifications and can be used as a new diarylethene
precursor to produce photoactive compounds with desired properties
and functions
Synthesis and Comparative Photoswitching Studies of Unsymmetrical 2,3-Diarylcyclopent-2-en-1-ones
Photochromic diarylethenes (DAEs)
based on the unsymmetrical ethene
“bridge” bearing heterocycles of the different nature
(oxazole and thiophene) as aromatic moieties have been designed and
the photoswitching properties have been studied. The comparative studies
of the photochromic characteristics of unsymmetrical isomeric 2,3-diarylcyclopent-2-en-1-ones
have shown that the isomers have different thermal stability, absorption
maxima, and quantum yields. It was found that the unsymmetrical diarylcyclopentenone
bearing at second position of the cyclopentenone ring the thiophene
unit displays high thermally stability, hypsochromic shift of absorption
maxima wavelengths of initial and cyclic forms, and high quantum yields
of cyclization and cycloreversion reactions. The replacement of the
carbonyl group with oxime leads to a reduction of the difference in
the photochromic properties of these isomers and just as the reduction
of the carbonyl group to the hydroxy-group negates this difference
to zero. The intramolecular hydrogen bond formation in the oxime and
hydroxy derivatives was confirmed by IR and <sup>1</sup>H NMR spectral
analysis, but the increase of the quantum yields of the cyclization
reaction in a nonpolar hexane is observed only in the case of hydroxy
derivatives that can be explained by the formation of more rigid six-membered
heterocycle in hydrogen bonding
Copper(II)-Mediated Aerobic Synthesis of Imidazo[1,2‑<i>a</i>]pyridines via Cascade Aminomethylation/Cycloisomerization of Alkynes
A single copper(II)-catalyzed three-component
cascade aminomethylation/cycloisomerization
of propiolates to form imidazo[1,2-<i>a</i>]pyridines
was explored. A straightforward method was developed for the practical
synthesis of functionalized imidazo[1,2-<i>a</i>]pyridines
from benzaldehydes, 2-aminopyridines, and propiolate derivatives
catalyzed by Cu(OAc)<sub>2</sub> hydrate in the presence of air. The
protocol is marked by excellent yields, functional group tolerance,
and, above all, adaptability to synthesize imidazo[1,2-<i>a</i>]pyridine-based drug molecules such as Alpidem
Photochemical Rearrangement of Diarylethenes: Reaction Efficiency and Substituent Effects
In
recent years, great synthetic potential of the photorearrangement
of diarylethenes leading to naphthalene derivatives via a cascade
process of photocyclization/[1,<i>n</i>]-H shift/cycloreversion
has been demonstrated. In this work, first a multifaceted study of
the influence of various factors on the efficiency of the photorearrangement
of diarylethenes of furanone series containing benzene and oxazole
derivatives as aryl residues has been carried out. The efficiency
of this phototransformation (quantum yields) and the effect of methoxy
substituents in the phenyl moiety have been studied. Despite the multistage
process, the quantum yields of the photorearrangement are rather high
(0.34–0.49). It has been found that the efficiency of photocyclization
of diarylethenes increases with the introduction of electron-donating
methoxy groups in the phenyl moiety. Using the DFT calculations, we
have been able to estimate in the photoinduced isomer the distance
between hydrogen atom and carbon atom to which it migrates in the
result of the sigmatropic shift. For all studied diarylethenes, this
value was 2.67–2.73 Å, which is less than the sum of van
der Waals radii of carbon and hydrogen atoms (2.9 Å)
Steroidal Pyrimidines and Dihydrotriazines as Novel Classes of Anticancer Agents against Hormone-Dependent Breast Cancer Cells
Most breast and prostate tumors are hormone-dependent, making it possible to use hormone therapy in patients with these tumors. The design of effective endocrine drugs that block the growth of tumors and have no severe side effects is a challenge. Thereupon, synthetic steroids are promising therapeutic drugs for the treatment of diseases such as hormone-dependent breast and prostate cancers. Here, we describe novel series of steroidal pyrimidines and dihydrotriazines with anticancer activities. A flexible approach to unknown pyrimidine and dihydrotriazine derivatives of steroids with selective control of the heterocyclization pattern is disclosed. A number of 18-nor-5α-androsta-2,13-diene[3,2-d]pyrimidine, androsta-2-ene[3,2-d]pyrimidine, Δ1, 3, 5(10)-estratrieno[16,17-d]pyrimidine, and 17-chloro-16-dihydrotriazine steroids were synthesized by condensations of amidines with β-chlorovinyl aldehydes derived from natural hormones. The synthesized compounds were screened for cytotoxicity against breast cancer cells and showed IC50 values of 7.4 μM and higher. Compounds were tested against prostate cancer cells and exhibited antiproliferative activity with IC50 values of 9.4 μM and higher comparable to that of cisplatin. Lead compound 4a displayed selectivity in ERα-positive breast cancer cells. At 10 μM concentration, this heterosteroid inhibited 50% of the E2-mediated ERα activity and led to partial ERα down-regulation. The ERα reporter assay and immunoblotting were supported by the docking study, which showed the probable binding mode of compound 4a to the estrogen receptor pocket. Thus, heterosteroid 4a proved to be a selective ERα modulator with the highest antiproliferative activity against hormone-dependent breast cancer and can be considered as a candidate for further anticancer drug development. In total, the synthesized heterosteroids may be considered as new promising classes of active anticancer agents
Triaryl-Substituted Divinyl Ketones Cyclization: Nazarov Reaction versus Friedel–Crafts Electrophilic Substitution
The acid-catalyzed cyclization
of a wide range of triaryl-substituted divinyl ketones has been studied.
It was found that the reaction pathway strongly depends on the nature
of the aryl substituent at the α-position to the carbonyl group.
An electron-rich aromatic substituent promotes the reaction to proceed
through the intramolecular Friedel–Crafts electrophilic substitution
giving dihydronaphthalene derivatives. In contrast, the presence
of an electron-deficient substituent is favorable for the Nazarov
4π-conrotatory cyclization yielding triaryl-substituted cyclopentenones.
The electrophilic substitution reaction was applied to thiophene and
thiazole derivatives
Structural and Spectral Properties of Photochromic Diarylethenes: Size Effect of the Ethene Bridge
The
effect of the size of the ethene bridge on the structural and
spectral properties of photochromic diarylethenes, which remains a
poorly understood phenomenon, was studied as applied to diarylethenes
containing unsymmetrical (cyclohexenone and cyclopentenone) and symmetrical
(cyclohexene and cyclopentene) ethene bridges. Thiophene, oxazole,
and imidazole derivatives were used as aryl moieties. An increase
in the size of the ethene bridge in the cycloalkenone series was found
to be accompanied by a hypsochromic shift of the absorption maximum
of the photoinduced form, whereas no difference was found for cycloalkenes.
A detailed analysis of the NMR spectra (including 2D experiments)
revealed previously unknown effects associated with the existence
of an intramolecular hydrogen bond (CH···N) between
the six-membered ethene bridge and the azole substituents. The NMR
experimental data obtained were confirmed by DFT quantum chemical
calculations and X-ray analysis. It was found that an intramolecular
hydrogen bond favors an increase of the quantum yield of the photocyclization
reaction
General Photoinduced Sequential Electrocyclization/[1,9]-Sigmatropic Rearrangement/Ring-Opening Reaction of Diarylethenes
A novel
and efficient photochemical transformation of diarylethenes
comprising a five-membered heterocyclic ring and phenyl moiety is
described. This reaction provides a simple method for the preparation
of functionalized naphthalene derivatives via photorearrangement reaction
of diarylethenes, and the process is characterized by high efficiency
that was determined by NMR monitoring. Some mechanistic aspects of
this process have been also explored. It was found that the reaction
includes tandem transformation of three basic processes: the photocyclization
of the hexatriene system, [1,9]-sigmatropic rearrangement, and heterocyclic
ring opening. Diarylethenes with different heterocycle moieties (thiophene,
benzo[<i>b</i>]thiophene, furan, indole, imidazole, thiazole,
oxazole, pyrazole) have been involved into this process, and the target
naphthalenes with good yields have been obtained. The opportunity
for use in the transformation of diarylethenes with different heterocyclic
residues permits synthesis of naphthalenes with desired functional
groups. The general character and high efficiency of the reaction
promise that the transformation can be an effective synthetic route
for the annulation of benzene rings to various aromatic systems, including
heterocycles