10 research outputs found
Cyclobutene Ring-Opening of Bicyclo[4.2.0]octa-1,6-dienes: Access to CF<sub>3</sub>‑Substituted 5,6,7,8-Tetrahydro-1,7-naphthyridines
An efficient method for the synthesis of novel CF<sub>3</sub>-substituted tetrahydro-1,7-naphthyridines including cyclic
α-amino acid derivatives has been developed. The method is based
on unusual cyclobutene ring-opening of bicyclo[4.2.0]Âocta-1,6-dienes
with pyrrolidine to afford the corresponding 1,5-diketones followed
by their heterocyclization. A convenient <i>one-pot</i> procedure
has been also elaborated starting from readily available trifluoromethylated
1,6-allenynes
Cyclobutene Ring-Opening of Bicyclo[4.2.0]octa-1,6-dienes: Access to CF<sub>3</sub>‑Substituted 5,6,7,8-Tetrahydro-1,7-naphthyridines
An efficient method for the synthesis of novel CF<sub>3</sub>-substituted tetrahydro-1,7-naphthyridines including cyclic
α-amino acid derivatives has been developed. The method is based
on unusual cyclobutene ring-opening of bicyclo[4.2.0]Âocta-1,6-dienes
with pyrrolidine to afford the corresponding 1,5-diketones followed
by their heterocyclization. A convenient <i>one-pot</i> procedure
has been also elaborated starting from readily available trifluoromethylated
1,6-allenynes
Coordination Chemistry of Mercury-Containing Anticrowns. Complexation of Perfluoro‑<i>o</i>,<i>o</i>′‑biphenylenemercury with <i>o</i>‑Xylene and Acetonitrile and the First X‑ray Diffraction Evidence for Its Trimeric Structure
The paper reports the first X-ray
diffraction data evidencing the
cyclic trimeric structure of the earlier synthesized octafluoro-<i>o</i>,<i>o</i>′-biphenylenemercury (<b>8</b>), being of considerable interest as a potential anticrown. The conclusion
on the trimeric (<i>o</i>,<i>o</i>′-C<sub>6</sub>F<sub>4</sub>C<sub>6</sub>F<sub>4</sub>Hg)<sub>3</sub> structure
of this mercuracycle is based on an X-ray structural analysis of its <i>o</i>-xylene and acetonitrile complexes {[(<i>o</i>,<i>o</i>′-C<sub>6</sub>F<sub>4</sub>C<sub>6</sub>F<sub>4</sub>Hg)<sub>3</sub>]Â(<i>o</i>-Me<sub>2</sub>C<sub>6</sub>H<sub>4</sub>)<sub>2</sub>} (<b>9</b>) and {[(<i>o</i>,<i>o</i>′-C<sub>6</sub>F<sub>4</sub>C<sub>6</sub>F<sub>4</sub>Hg)<sub>3</sub>]Â(MeCN)<sub>3</sub>} (<b>10</b>), which were obtained from <b>8</b> in an analytically
pure state and fully characterized. Complex <b>9</b> contains
two <i>o</i>-xylene species per one molecule of <b>8</b> and forms in the crystal infinite chains consisting of alternating
mercuramacrocycle units and bridging <i>o</i>-xylene ligands.
One more <i>o</i>-xylene molecule in each macrocyclic fragment
of the chain serves as a terminal ligand. Both bridging and terminal
molecules of <i>o</i>-xylene are coordinated in all cases
with only one Hg site of the corresponding mercuracycle. The back
transformation of complex <b>9</b> into <b>8</b> and <i>o</i>-xylene occurs on its heating in a vacuum at 100–120
°C for 2 h. In contrast to <b>9</b>, complex <b>10</b>, containing three acetonitrile ligands per one molecule of <b>8</b>, has a discrete structure in the crystal. In this complex,
two of three acetonitrile species are bonded to one and the same Hg
center of <b>8</b>, whereas the third MeCN species is coordinated
with the other Hg atom of the mercuramacrocycle
Coordination Chemistry of Anticrowns. Synthesis and Structures of Double-Decker Sandwich Complexes of the Three-Mercury Anticrown (<i>o</i>‑C<sub>6</sub>F<sub>4</sub>Hg)<sub>3</sub> with Halide Anions Containing and Not Containing Coordinated Dibromomethane Molecules
The
interaction of the three-mercury anticrown (<i>o</i>-C<sub>6</sub>F<sub>4</sub>Hg)<sub>3</sub> (<b>1</b>) with
[PPh<sub>4</sub>]Â[BF<sub>4</sub>] in methanol at room temperature
leads to fluoride anion transfer from BF<sub>4</sub><sup>–</sup> to <b>1</b> with the formation of a fluoride complex, [PPh<sub>4</sub>]Â{[(<i>o</i>-C<sub>6</sub>F<sub>4</sub>Hg)<sub>3</sub>]<sub>2</sub>F}, having a
double-decker sandwich structure. The fluoride ion in this unique
adduct is disposed between the mutually parallel planes of the central
nine-membered rings of the anticrown units and cooperatively coordinated
by all six Hg sites. The iodide anion also forms a double-decker sandwich
in the interaction with <b>1</b>, but this sandwich, [PPh<sub>4</sub>]Â{[(<i>o</i>-C<sub>6</sub>F<sub>4</sub>Hg)<sub>3</sub>]<sub>2</sub>I}, has a wedge-shaped geometry. The reaction of <b>1</b> with [<sup><i>n</i></sup>Bu<sub>4</sub>N]Cl in
dibromomethane at −15 °C affords a complex, [<sup><i>n</i></sup>Bu<sub>4</sub>N]Â{[(<i>o</i>-C<sub>6</sub>F<sub>4</sub>Hg)<sub>3</sub>]<sub>2</sub>ClÂ(CH<sub>2</sub>Br<sub>2</sub>)<sub>2</sub>}, containing one chloride anion and two coordinated
CH<sub>2</sub>Br<sub>2</sub> species per two molecules of <b>1</b>. A similar bromide complex of <b>1</b>, containing two coordinated
CH<sub>2</sub>Br<sub>2</sub> moieties, has also been synthesized and
structurally characterized. Both compounds represent wedge-shaped
double-decker sandwiches wherein the halide anion is simultaneously
bonded to all Hg centers of the anticrown molecules. The dibromomethane
species in the isolated adducts are also arranged in the space between
the mercuramacrocycles. One of these species is coordinated by each
of its bromine atoms to a single Hg site of the adjacent macrocycle
while the other interacts by only one bromine atom with a Hg center
of the neighboring molecule of <b>1</b>
Coordination Chemistry of Anticrowns. Synthesis and Structures of Double-Decker Sandwich Complexes of the Three-Mercury Anticrown (<i>o</i>‑C<sub>6</sub>F<sub>4</sub>Hg)<sub>3</sub> with Halide Anions Containing and Not Containing Coordinated Dibromomethane Molecules
The
interaction of the three-mercury anticrown (<i>o</i>-C<sub>6</sub>F<sub>4</sub>Hg)<sub>3</sub> (<b>1</b>) with
[PPh<sub>4</sub>]Â[BF<sub>4</sub>] in methanol at room temperature
leads to fluoride anion transfer from BF<sub>4</sub><sup>–</sup> to <b>1</b> with the formation of a fluoride complex, [PPh<sub>4</sub>]Â{[(<i>o</i>-C<sub>6</sub>F<sub>4</sub>Hg)<sub>3</sub>]<sub>2</sub>F}, having a
double-decker sandwich structure. The fluoride ion in this unique
adduct is disposed between the mutually parallel planes of the central
nine-membered rings of the anticrown units and cooperatively coordinated
by all six Hg sites. The iodide anion also forms a double-decker sandwich
in the interaction with <b>1</b>, but this sandwich, [PPh<sub>4</sub>]Â{[(<i>o</i>-C<sub>6</sub>F<sub>4</sub>Hg)<sub>3</sub>]<sub>2</sub>I}, has a wedge-shaped geometry. The reaction of <b>1</b> with [<sup><i>n</i></sup>Bu<sub>4</sub>N]Cl in
dibromomethane at −15 °C affords a complex, [<sup><i>n</i></sup>Bu<sub>4</sub>N]Â{[(<i>o</i>-C<sub>6</sub>F<sub>4</sub>Hg)<sub>3</sub>]<sub>2</sub>ClÂ(CH<sub>2</sub>Br<sub>2</sub>)<sub>2</sub>}, containing one chloride anion and two coordinated
CH<sub>2</sub>Br<sub>2</sub> species per two molecules of <b>1</b>. A similar bromide complex of <b>1</b>, containing two coordinated
CH<sub>2</sub>Br<sub>2</sub> moieties, has also been synthesized and
structurally characterized. Both compounds represent wedge-shaped
double-decker sandwiches wherein the halide anion is simultaneously
bonded to all Hg centers of the anticrown molecules. The dibromomethane
species in the isolated adducts are also arranged in the space between
the mercuramacrocycles. One of these species is coordinated by each
of its bromine atoms to a single Hg site of the adjacent macrocycle
while the other interacts by only one bromine atom with a Hg center
of the neighboring molecule of <b>1</b>
Indenyl Rhodium Complexes with Arene Ligands: Synthesis and Application for Reductive Amination
An
efficient protocol for synthesis of indenyl rhodium complexes
with arene ligands has been developed. The hexafluoroantimonate salts
[(η<sup>5</sup>-indenyl)ÂRhÂ(arene)]Â(SbF<sub>6</sub>)<sub>2</sub> (arene = benzene (<b>2a</b>), <i>o</i>-xylene (<b>2b</b>), mesitylene (<b>2c</b>), durene (<b>2d</b>), hexamethylbenzene (<b>2e</b>), and [2.2]Âparacyclophane (<b>2g</b>)) were obtained by iodide abstraction from [(η<sup>5</sup>-indenyl)ÂRhI<sub>2</sub>]<sub><i>n</i></sub> (<b>1</b>) with AgSbF<sub>6</sub> in the presence of benzene and its
derivatives. The procedure is also suitable for the synthesis of the
dirhodium arene complex [(μ-η:η′-1,3-dimesitylpropane)Â{RhÂ(η<sup>5</sup>-indenyl)}<sub>2</sub>]Â(SbF<sub>6</sub>)<sub>4</sub> (<b>3</b>) starting from 1,3-dimesitylpropane. The structures of [<b>2e</b>]Â(SbF<sub>6</sub>)<sub>2</sub>, [<b>2g</b>]Â(SbF<sub>6</sub>)<sub>2</sub>, and [<b>3</b>]Â(SbF<sub>6</sub>)<sub>4</sub> were determined by X-ray diffraction. The last species has a sterically
unfavorable conformation, in which the bridgehead carbon atoms of
the indenyl ligand are arranged close to the propane linker between
two mesitylene moieties. Experimental and DFT calculation data revealed
that the benzene ligand in <b>2a</b> is more labile than that
in the related cyclopentadienyl complexes [(C<sub>5</sub>R<sub>5</sub>)ÂRhÂ(C<sub>6</sub>H<sub>6</sub>)]<sup>2+</sup>. Complex <b>2c</b> effectively catalyzes the reductive amination reaction between aldehydes
and primary (or secondary) amines in the presence of carbon monoxide,
giving the corresponding secondary and tertiary amines in very high
yields (80–99%). This protocol is the most active in water
Indenyl Rhodium Complexes with Arene Ligands: Synthesis and Application for Reductive Amination
An
efficient protocol for synthesis of indenyl rhodium complexes
with arene ligands has been developed. The hexafluoroantimonate salts
[(η<sup>5</sup>-indenyl)ÂRhÂ(arene)]Â(SbF<sub>6</sub>)<sub>2</sub> (arene = benzene (<b>2a</b>), <i>o</i>-xylene (<b>2b</b>), mesitylene (<b>2c</b>), durene (<b>2d</b>), hexamethylbenzene (<b>2e</b>), and [2.2]Âparacyclophane (<b>2g</b>)) were obtained by iodide abstraction from [(η<sup>5</sup>-indenyl)ÂRhI<sub>2</sub>]<sub><i>n</i></sub> (<b>1</b>) with AgSbF<sub>6</sub> in the presence of benzene and its
derivatives. The procedure is also suitable for the synthesis of the
dirhodium arene complex [(μ-η:η′-1,3-dimesitylpropane)Â{RhÂ(η<sup>5</sup>-indenyl)}<sub>2</sub>]Â(SbF<sub>6</sub>)<sub>4</sub> (<b>3</b>) starting from 1,3-dimesitylpropane. The structures of [<b>2e</b>]Â(SbF<sub>6</sub>)<sub>2</sub>, [<b>2g</b>]Â(SbF<sub>6</sub>)<sub>2</sub>, and [<b>3</b>]Â(SbF<sub>6</sub>)<sub>4</sub> were determined by X-ray diffraction. The last species has a sterically
unfavorable conformation, in which the bridgehead carbon atoms of
the indenyl ligand are arranged close to the propane linker between
two mesitylene moieties. Experimental and DFT calculation data revealed
that the benzene ligand in <b>2a</b> is more labile than that
in the related cyclopentadienyl complexes [(C<sub>5</sub>R<sub>5</sub>)ÂRhÂ(C<sub>6</sub>H<sub>6</sub>)]<sup>2+</sup>. Complex <b>2c</b> effectively catalyzes the reductive amination reaction between aldehydes
and primary (or secondary) amines in the presence of carbon monoxide,
giving the corresponding secondary and tertiary amines in very high
yields (80–99%). This protocol is the most active in water
Coordination Chemistry of Anticrowns. Isolation of the Chloride Complex of the Four-Mercury Anticrown {[(<i>o</i>,<i>o</i>′‑C<sub>6</sub>F<sub>4</sub>C<sub>6</sub>F<sub>4</sub>Hg)<sub>4</sub>]Cl}<sup>−</sup> from the Reaction of <i>o</i>,<i>o</i>′‑Dilithiooctafluorobiphenyl with HgCl<sub>2</sub> and Its Transformations to the Free Anticrown and the Complexes with <i>o</i>‑Xylene, Acetonitrile, and Acetone
The paper reports
that the interaction of <i>o</i>,<i>o</i>′-dilithiooctafluorobiphenyl
with HgCl<sub>2</sub> in ether results in the formation of the lithium
chloride complex
LiÂ{[(<i>o</i>,<i>o</i>′-C<sub>6</sub>F<sub>4</sub>C<sub>6</sub>F<sub>4</sub>Hg)<sub>4</sub>]ÂCl} (<b>11</b>) of the four-mercury anticrown (<i>o</i>,<i>o</i>′-C<sub>6</sub>F<sub>4</sub>C<sub>6</sub>F<sub>4</sub>Hg)<sub>4</sub> (<b>12</b>) along with the earlier isolated and characterized
three-mercury anticrown (<i>o</i>,<i>o</i>′-C<sub>6</sub>F<sub>4</sub>C<sub>6</sub>F<sub>4</sub>Hg)<sub>3</sub> (<b>2</b>). The complex was identified by the reaction with 12-crown-4
and determination of the structure of the [LiÂ(12-crown-4)<sub>2</sub>]Â{[(<i>o</i>,<i>o</i>′-C<sub>6</sub>F<sub>4</sub>C<sub>6</sub>F<sub>4</sub>Hg)<sub>4</sub>]ÂCl} (<b>13</b>) formed. According to an X-ray analysis, the chloride anion in <b>13</b> is simultaneously coordinated with all four Hg centers
of the anticrown, forming with them a pyramidal Hg<sub>4</sub>Cl fragment.
The reaction of <b>11</b> (in the form of an acetonitrile solvate, <b>11</b>·<i>n</i>MeCN) with boiling water leads to
removal of LiCl from <b>11</b> and to the formation of free
anticrown <b>12</b>, the subsequent recrystallization of which
from <i>o</i>-xylene affords the <i>o</i>-xylene
complex {[(<i>o</i>,<i>o</i>′-C<sub>6</sub>F<sub>4</sub>C<sub>6</sub>F<sub>4</sub>Hg)<sub>4</sub>]Â(<i>o</i>-Me<sub>2</sub>C<sub>6</sub>H<sub>4</sub>)<sub>2</sub>} (<b>14</b>). The obtained <b>14</b> forms in the crystal infinite chains
consisting of alternating anticrown units and bridging <i>o</i>-xylene moieties. Another <i>o</i>-xylene molecule in each
macrocyclic fragment of the chain plays the role of a terminal ligand.
In both cases, the <i>o</i>-xylene ligands in <b>14</b> are bonded to only one Hg center of the corresponding mercuramacrocycle.
The back-conversion of complex <b>14</b> into <b>12</b> and <i>o</i>-xylene proceeds in the course of its thermal
decomposition under vacuum at 100–120 °C. The reaction
of <b>12</b> with acetonitrile yields the nitrile complex {[(<i>o</i>,<i>o</i>′-C<sub>6</sub>F<sub>4</sub>C<sub>6</sub>F<sub>4</sub>Hg)<sub>4</sub>]Â(MeCN)<sub>2</sub>} (<b>15</b>), which also forms infinite polymeric chains in the crystal. In
each monomeric unit of the chain, the corresponding bridging nitrile
is bonded to only one mercury atom of the anticrown moiety, whereas
the other nitrile ligand is coordinated with two Hg sites. The synthesis
and structure of the complex {[(<i>o</i>,<i>o</i>′-C<sub>6</sub>F<sub>4</sub>C<sub>6</sub>F<sub>4</sub>Hg)<sub>4</sub>]Â(Me<sub>2</sub>CO)<sub>2</sub>(H<sub>2</sub>O)} (<b>16</b>), containing two acetone and one water ligand per molecule of <b>12</b>, are also reported. Each acetone molecule in <b>16</b> interacts with only one Hg atom of <b>12</b>, while the water
molecule is coordinated with two mercury centers and, in addition,
forms H-bonds with the oxygen atoms of the acetone species
Highly Cytotoxic Palladium(II) Pincer Complexes Based on Picolinylamides Functionalized with Amino Acids Bearing Ancillary <i>S</i>‑Donor Groups
The reactions of
picolinyl and 4-chloropicolinyl chlorides with methyl esters of <i>S</i>-methyl-l-cysteine, l- and d-methionine, and l-histidine afforded a series of functionalized
carboxamides, which readily formed pincer-type complexes upon interaction
with PdCl<sub>2</sub>(NCPh)<sub>2</sub> in solution under mild conditions.
The direct cyclopalladation of the ligands derived was also accomplished
in the solid phase, in particular, mechanochemically, although it
was complicated by the partial deactivation of the starting amides.
The resulting complexes with 5,5- and 5,6-membered fused metallocycles
were fully characterized by IR and NMR spectroscopy, including variable-temperature
and 2D-NMR studies. In the case of some cysteine- and methionine-based
derivatives, the realization of κ<sup>3</sup>-<i>N,N,S-</i>coordination was supported by X-ray diffraction. The cytotoxic effects
of these complexes were examined on HCT116, MCF7, and PC3 human cancer
cell lines as well as HEK293 as a representative of normal cells.
The comparative studies allowed us to determine that the presence
of the sulfide ancillary donor group is crucial for cytotoxic activity
of this type of PdÂ(II) complexes. The main structure–activity
relationships and the most promising palladocycles were outlined.
The additional studies by gel electrophoresis revealed that 4-chloropicolinyl
derivatives, despite the nature of an amino acid, can bind with DNA
and inhibit topoisomerase I activity
Polyphenylenepyridyl Dendrons with Functional Periphery and Focal Points: Syntheses and Applications
For
the first time we report syntheses of a family of functional
polyphenylenepyridyl dendrons with different generations and structures
such as focal groups, periphery, and a combination of phenylene and
pyridyl moieties in the dendron interior using a Diels–Alder
approach and a divergent method. The dendron structure and composition
were confirmed using NMR spectroscopy, MALDI-TOF mass spectrometry,
FTIR, and elemental analysis. As a proof of concept that these dendrons
can be successfully used for the development of nanocomposites, synthesis
of iron oxide nanoparticles was carried out in the presence of thermally
stable dendrons as capping molecules followed by formation of Pd NPs
in the dendron shells. This resulted in magnetically recoverable catalysts
exhibiting exceptional performance in selective hydrogenation of dimethylethynylcarbinol
(DMEC) to dimethylvinylcarbinol (DMVC)