The role of polynuclear species in C-H activations assisted by palladium carboxylates has not bee... more The role of polynuclear species in C-H activations assisted by palladium carboxylates has not been clear so far. The summary of the key findings covering this issue shows its important role under certain conditions. However, much more effort is necessary for a deeper understanding of the whole issue. Scheme 1 Simplified reaction mechanism of remote group directed C-H activation reaction. Fig. 1 Products of the reaction of palladium acetate with nucleophiles.
Zenodo (CERN European Organization for Nuclear Research), Nov 1, 2017
Reactions catalyzed by palladium(II) acetate and trifluoroacetic acid (TFA) have a clear preactiv... more Reactions catalyzed by palladium(II) acetate and trifluoroacetic acid (TFA) have a clear preactivation phase. However, the structure of real catalytic species remains unclear. We show that the key species are cyclic trinuclear complexes of composition [Pd3(OAc)6-x(OTFA)x] (x = 1 -6) formed by a sequential ligand exchange from [Pd3(OAc)6]. Furthermore, we prove that the trinuclear palladium backbone of the precatalyst remains preserved during the first phase of the C-H activation reaction of acetanilides. In other words, reaction pathway including the trinuclear species should be taken into account in discussion about mechanisms of the reactions catalyzed by palladium acetates.
2019). Silica coated iron oxide nanoparticles-induced cytotoxicity, genotoxicity and its underlyi... more 2019). Silica coated iron oxide nanoparticles-induced cytotoxicity, genotoxicity and its underlying mechanism in human HK-2 renal proximal tubule epithelial cells.
Diphyllin is a natural arylnaphtalide lignan extracted from tropical plants of particular importa... more Diphyllin is a natural arylnaphtalide lignan extracted from tropical plants of particular importance in traditional Chinese medicine. This compound has been described as a potent inhibitor of vacuolar (H + )ATPases and hence of the endosomal acidification process that is required by numerous enveloped viruses to trigger their respective viral infection cascades after entering host cells by receptor-mediated endocytosis. Accordingly, we report here a revised, updated, and improved synthesis of diphyllin, and demonstrate its antiviral activities against a panel of enveloped viruses from Flaviviridae, Phenuiviridae, Rhabdoviridae, and Herpesviridae families. Diphyllin is not cytotoxic for Vero and BHK-21 cells up to 100 µM and exerts a sub-micromolar or low-micromolar antiviral activity against tick-borne encephalitis virus, West Nile virus, Zika virus, Rift Valley fever virus, rabies virus, and herpes-simplex virus type 1. Our study shows that diphyllin is a broad-spectrum host cell-targeting antiviral agent that blocks the replication of multiple phylogenetically unrelated enveloped RNA and DNA viruses. In support of this, we also demonstrate that diphyllin is more than just a vacuolar (H + )ATPase inhibitor but may employ other antiviral mechanisms of action to inhibit the replication cycles of those viruses that do not enter host cells by endocytosis followed by low pH-dependent membrane fusion.
Diphyllin is a natural arylnaphtalide lignan extracted from tropical plants of particular importa... more Diphyllin is a natural arylnaphtalide lignan extracted from tropical plants of particular importance in traditional Chinese medicine. This compound has been described as a potent inhibitor of vacuolar (H+)ATPases and hence of the endosomal acidification process that is required by numerous enveloped viruses to trigger their respective viral infection cascades after entering host cells by receptor-mediated endocytosis. Accordingly, we report here a revised, updated, and improved synthesis of diphyllin, and demonstrate its antiviral activities against a panel of enveloped viruses from Flaviviridae, Phenuiviridae, Rhabdoviridae, and Herpesviridae families. Diphyllin is not cytotoxic for Vero and BHK-21 cells up to 100 µM and exerts a sub-micromolar or low-micromolar antiviral activity against tick-borne encephalitis virus, West Nile virus, Zika virus, Rift Valley fever virus, rabies virus, and herpes-simplex virus type 1. Our study shows that diphyllin is a broad-spectrum host cell-tar...
The role of polynuclear species in C–H activations assisted by palladium carboxylates has not bee... more The role of polynuclear species in C–H activations assisted by palladium carboxylates has not been clear so far.
New 2,6-bis(5-alkyl-1,5-dimethyl-4,5-dihydro-1H-imidazol-4-on-2-yl)pyridines have been prepared a... more New 2,6-bis(5-alkyl-1,5-dimethyl-4,5-dihydro-1H-imidazol-4-on-2-yl)pyridines have been prepared and characterized by 1H-, 13C-NMR and elemental analysis. These ligands form complexes with FeCl2, which were isolated and characterized by elemental analysis and MS. Both in the solid phase and in aqueous and methanolic solutions the complexes have two ligand molecules per one ferrous ion. By means of the kinetic stopped-flow method, the rate constants
Fe(III)(BIAP)Cl3 complex catalyzes alkylative cyclization of 2-chloro-1,7-heptadiene in the prese... more Fe(III)(BIAP)Cl3 complex catalyzes alkylative cyclization of 2-chloro-1,7-heptadiene in the presence of triethylaluminum. It also catalyzes deallylation of certain 2-allyl-2-substituted malonates under the same reaction conditions.
ABSTRACT Acylation of 2-amino-N-methyl-thiobenzamide with substituted benzoyl chlorides has been ... more ABSTRACT Acylation of 2-amino-N-methyl-thiobenzamide with substituted benzoyl chlorides has been used to synthesize the corresponding 2-benzoylamino-N-methylthiobenzamides. Subsequent sodium methoxide-catalyzed ring closure gives the corresponding 3-methyl-2-phenylquinazoline-4-thiones. These compounds were characterized by means of their 1H- and 12C-NMR spectra. The kinetics of the cyclization reaction has been followed with UV-VIS spectroscopy at 100 °C in methanolic solutions of sodium methoxide.
magnified image The reaction of aldehydes (pentanal, benzaldehyde, 4‐methoxybenzaldehyde, 4‐nitro... more magnified image The reaction of aldehydes (pentanal, benzaldehyde, 4‐methoxybenzaldehyde, 4‐nitrobenzaldehyde, salicylaldehyde, pyridin‐2‐carbaldehyde) with 1‐aminocyclopentancarboxamide or (S)‐2‐amino‐2,3‐dimethylbutanamide has been used to prepare substituted imidazolidin‐4‐ones 1a, 1b, 1c, 1d, 1e, 1f, 1g (a: R1 = CH3(CH2)3; b: R1 = C6H5; c: R1 = 4‐CH3OC6H4; d: R1 = 4‐NO2C6H4; e: R1 = 2‐HOC6H4; f: R1 = 2‐pyridyl; for R2 = R3 = (CH2)4), and g: R1 = 2‐pyridyl; for R2 = CH3; R3 = CH(CH3)2) in the yields of 53–83%. Subsequent oxidations with various reagents gave the corresponding 4,5‐dihydro‐1H‐imidazol‐5‐ones 2a, 2b, 2c, 2d, 2e, 2f, 2g: Pd/C (72–93%), DDQ (25–80%), and MnO2 (30–77%). Structure of the prepared compounds 1a, 1b, 1c, 1d, 1e, 1f, 1g and 2a, 2b, 2c, 2d, 2e, 2f, 2g was verified by 1H NMR and 13C NMR spectroscopy, EI‐MS and elemental analysis. X‐ray diffraction was performed in the case of compounds 1e and 2e. J. Heterocyclic Chem., (2010).
ABSTRACT (Chemical Equation Presented) A new method for the synthesis of substituted 5-(2-hydroxy... more ABSTRACT (Chemical Equation Presented) A new method for the synthesis of substituted 5-(2-hydroxyethyl)-2-phenylimino-1,3-thiazolidin-4-ones and 5-(2-hydroxyethyl)-2-phenylamino-4,5-dihydro-1,3-thiazol-4-ones is described, starting from phenylthioureas and 3-bromotetrahydrofuran-2-one. The reaction proceeds under mild conditions, is very simple to perform, and is applicable to a relatively wide range of substituents in benzene nucleus. Some 1,3-thiazolidin-4-ones show dynamic NMR behavior in solution because of prototropy tautomerism and E-/Z-stereoisomerism.
Collection of Czechoslovak Chemical Communications, 1989
The intramolecular nucleophilic addition of N-methyl-N-(2,4,6-trinitrophenyl)glycine anion in met... more The intramolecular nucleophilic addition of N-methyl-N-(2,4,6-trinitrophenyl)glycine anion in methanol-dimethyl sulfoxide mixtures produces spiro[(3-methyl-5-oxazolidinone)-2,1'-(2',4',6'-trinitrobenzenide)]. The spiro adduct has been identified by means of 1H and 13C NMR spectroscopy. This is the first case when the formation of a Meisenheimer adduct with carboxylate ion is observed. Logarithm of the equilibrium constant of adduct formation increases linearly with the mole fraction of dimethyl sulfoxide in its mixture with methanol.
A complex derived from the enantiomeric bipiperidine and copper(II) acetate hydrate is an efficie... more A complex derived from the enantiomeric bipiperidine and copper(II) acetate hydrate is an efficient catalyst for the enantioselective Henry reaction. The easy availability of both catalyst components, mild reaction conditions, high yield, and good to excellent enantioselectivity make the catalyst useful for everyday practice.
The Henry reaction was catalyzed by 0.01 equiv of aminopropylated nanosilica particles (nano-NAP)... more The Henry reaction was catalyzed by 0.01 equiv of aminopropylated nanosilica particles (nano-NAP) in refluxing nitroalkanes to provide nitrostyrenes in good yields. The catalyst could be recycled up to three times in 76% average yield.
Kinetic evidence has indicated that methanolysis of synthesized 4-acetoxybenzyl carbamates procee... more Kinetic evidence has indicated that methanolysis of synthesized 4-acetoxybenzyl carbamates proceeds via a one-step (concerted) mechanism. Concerted 1,6-elimination produces the very reactive 1,4-quinonemethide, which was trapped in the form of 4-methoxymethylphenol. The inhibition activity of benzyl N-phenylcarbamates to acetylcholinesterase (ACHE) and butyrylcholinesterase (BCHE) was also tested. The found IC 50 values varied within the limits of 199-535 µmol•l -1 for ACHE and 21-177 µmol•l -1 for BCHE. The found values of partition coefficient (P ow ) in the range of 1.5-11.5 represent a prerequisite of good transport of benzyl Nphenylcarbamates through haemato-encephalic barrier.
The synthesis of a water soluble azo initiators from 2,2'-azodiisobutyronitrile (AIBN) was perfor... more The synthesis of a water soluble azo initiators from 2,2'-azodiisobutyronitrile (AIBN) was performed in three steps: reaction of dinitrile with aromatic alcohols in the presence of HCl to form bisiminoesters hydrochlorides which are hydrolyzed to the esters and final regioselective sulfonation of the aromatic esters. The thermal decomposition of the azo initiators obtained leads to formation of two surface active radicals which can start the chain reaction.
The human drugs – antibiotic Linezolid (1) and anticoagulant Rivaroxaban (2) – belongs among mode... more The human drugs – antibiotic Linezolid (1) and anticoagulant Rivaroxaban (2) – belongs among modern pharmaceutics, which contain oxazolidine-2-one moiety bearing stereogenic centre. The chirality of these drugs is fundamental attribute of their biological activity. Herein, one of the efficient asymmetric syntheses of those drugs was studied in detail. High enantioselective catalysts were tested in the key step of the synthetic procedure, i.e. asymmetric Henry reaction, under different reaction conditions, using several starting aldehydes. The corresponding nitroaldols as chiral intermediates of those drugs were obtained in high yields and enantiomeric excess up to 91% ee.
A family of oxazaborines, diazaborinones, triazaborines, and triazaborinones was prepared by reac... more A family of oxazaborines, diazaborinones, triazaborines, and triazaborinones was prepared by reaction of polarized ethylenes, such as β-enaminoamides, with 4-methylbenzenediazonium tetraphenylborates. The reaction conditions (stirring in CH2Cl2 at room temperature (Method A) or stirring with CH3COONa in CH2Cl2 at room temperature (Method B) or refluxing in the CH2Cl2/toluene mixture (Method C)) controlled the formation and relative content of these compounds in the reaction mixtures from one to three products. Substituted oxazaborines gradually rearranged into diazaborinones at 250 °C. The prepared compounds were characterized by 1H NMR, 13C NMR, IR, and UV–Vis spectroscopy, HRMS, or microanalysis. The structure of individual compounds was confirmed by 11B NMR, 15N NMR, 1D NOESY, and X-ray analysis. The mechanism of reaction of enaminoamides with 4-methylbenzenediazonium tetraphenylborate was proposed.
The transition metal (palladium)-catalysed asymmetric 1,4-addition of arylboronic acids to conjug... more The transition metal (palladium)-catalysed asymmetric 1,4-addition of arylboronic acids to conjugated enones belong to the most important and emerging strategies for the construction of C–C bonds in an asymmetric fashion. This review covers known catalytic systems used for this transformation. For clarity, we are using the type of ligand as a sorting criterion. Finally, we attempted to create a flowchart facilitating the selection of a suitable ligand for a given combination of enone and arylboronic acid.
The role of polynuclear species in C-H activations assisted by palladium carboxylates has not bee... more The role of polynuclear species in C-H activations assisted by palladium carboxylates has not been clear so far. The summary of the key findings covering this issue shows its important role under certain conditions. However, much more effort is necessary for a deeper understanding of the whole issue. Scheme 1 Simplified reaction mechanism of remote group directed C-H activation reaction. Fig. 1 Products of the reaction of palladium acetate with nucleophiles.
Zenodo (CERN European Organization for Nuclear Research), Nov 1, 2017
Reactions catalyzed by palladium(II) acetate and trifluoroacetic acid (TFA) have a clear preactiv... more Reactions catalyzed by palladium(II) acetate and trifluoroacetic acid (TFA) have a clear preactivation phase. However, the structure of real catalytic species remains unclear. We show that the key species are cyclic trinuclear complexes of composition [Pd3(OAc)6-x(OTFA)x] (x = 1 -6) formed by a sequential ligand exchange from [Pd3(OAc)6]. Furthermore, we prove that the trinuclear palladium backbone of the precatalyst remains preserved during the first phase of the C-H activation reaction of acetanilides. In other words, reaction pathway including the trinuclear species should be taken into account in discussion about mechanisms of the reactions catalyzed by palladium acetates.
2019). Silica coated iron oxide nanoparticles-induced cytotoxicity, genotoxicity and its underlyi... more 2019). Silica coated iron oxide nanoparticles-induced cytotoxicity, genotoxicity and its underlying mechanism in human HK-2 renal proximal tubule epithelial cells.
Diphyllin is a natural arylnaphtalide lignan extracted from tropical plants of particular importa... more Diphyllin is a natural arylnaphtalide lignan extracted from tropical plants of particular importance in traditional Chinese medicine. This compound has been described as a potent inhibitor of vacuolar (H + )ATPases and hence of the endosomal acidification process that is required by numerous enveloped viruses to trigger their respective viral infection cascades after entering host cells by receptor-mediated endocytosis. Accordingly, we report here a revised, updated, and improved synthesis of diphyllin, and demonstrate its antiviral activities against a panel of enveloped viruses from Flaviviridae, Phenuiviridae, Rhabdoviridae, and Herpesviridae families. Diphyllin is not cytotoxic for Vero and BHK-21 cells up to 100 µM and exerts a sub-micromolar or low-micromolar antiviral activity against tick-borne encephalitis virus, West Nile virus, Zika virus, Rift Valley fever virus, rabies virus, and herpes-simplex virus type 1. Our study shows that diphyllin is a broad-spectrum host cell-targeting antiviral agent that blocks the replication of multiple phylogenetically unrelated enveloped RNA and DNA viruses. In support of this, we also demonstrate that diphyllin is more than just a vacuolar (H + )ATPase inhibitor but may employ other antiviral mechanisms of action to inhibit the replication cycles of those viruses that do not enter host cells by endocytosis followed by low pH-dependent membrane fusion.
Diphyllin is a natural arylnaphtalide lignan extracted from tropical plants of particular importa... more Diphyllin is a natural arylnaphtalide lignan extracted from tropical plants of particular importance in traditional Chinese medicine. This compound has been described as a potent inhibitor of vacuolar (H+)ATPases and hence of the endosomal acidification process that is required by numerous enveloped viruses to trigger their respective viral infection cascades after entering host cells by receptor-mediated endocytosis. Accordingly, we report here a revised, updated, and improved synthesis of diphyllin, and demonstrate its antiviral activities against a panel of enveloped viruses from Flaviviridae, Phenuiviridae, Rhabdoviridae, and Herpesviridae families. Diphyllin is not cytotoxic for Vero and BHK-21 cells up to 100 µM and exerts a sub-micromolar or low-micromolar antiviral activity against tick-borne encephalitis virus, West Nile virus, Zika virus, Rift Valley fever virus, rabies virus, and herpes-simplex virus type 1. Our study shows that diphyllin is a broad-spectrum host cell-tar...
The role of polynuclear species in C–H activations assisted by palladium carboxylates has not bee... more The role of polynuclear species in C–H activations assisted by palladium carboxylates has not been clear so far.
New 2,6-bis(5-alkyl-1,5-dimethyl-4,5-dihydro-1H-imidazol-4-on-2-yl)pyridines have been prepared a... more New 2,6-bis(5-alkyl-1,5-dimethyl-4,5-dihydro-1H-imidazol-4-on-2-yl)pyridines have been prepared and characterized by 1H-, 13C-NMR and elemental analysis. These ligands form complexes with FeCl2, which were isolated and characterized by elemental analysis and MS. Both in the solid phase and in aqueous and methanolic solutions the complexes have two ligand molecules per one ferrous ion. By means of the kinetic stopped-flow method, the rate constants
Fe(III)(BIAP)Cl3 complex catalyzes alkylative cyclization of 2-chloro-1,7-heptadiene in the prese... more Fe(III)(BIAP)Cl3 complex catalyzes alkylative cyclization of 2-chloro-1,7-heptadiene in the presence of triethylaluminum. It also catalyzes deallylation of certain 2-allyl-2-substituted malonates under the same reaction conditions.
ABSTRACT Acylation of 2-amino-N-methyl-thiobenzamide with substituted benzoyl chlorides has been ... more ABSTRACT Acylation of 2-amino-N-methyl-thiobenzamide with substituted benzoyl chlorides has been used to synthesize the corresponding 2-benzoylamino-N-methylthiobenzamides. Subsequent sodium methoxide-catalyzed ring closure gives the corresponding 3-methyl-2-phenylquinazoline-4-thiones. These compounds were characterized by means of their 1H- and 12C-NMR spectra. The kinetics of the cyclization reaction has been followed with UV-VIS spectroscopy at 100 °C in methanolic solutions of sodium methoxide.
magnified image The reaction of aldehydes (pentanal, benzaldehyde, 4‐methoxybenzaldehyde, 4‐nitro... more magnified image The reaction of aldehydes (pentanal, benzaldehyde, 4‐methoxybenzaldehyde, 4‐nitrobenzaldehyde, salicylaldehyde, pyridin‐2‐carbaldehyde) with 1‐aminocyclopentancarboxamide or (S)‐2‐amino‐2,3‐dimethylbutanamide has been used to prepare substituted imidazolidin‐4‐ones 1a, 1b, 1c, 1d, 1e, 1f, 1g (a: R1 = CH3(CH2)3; b: R1 = C6H5; c: R1 = 4‐CH3OC6H4; d: R1 = 4‐NO2C6H4; e: R1 = 2‐HOC6H4; f: R1 = 2‐pyridyl; for R2 = R3 = (CH2)4), and g: R1 = 2‐pyridyl; for R2 = CH3; R3 = CH(CH3)2) in the yields of 53–83%. Subsequent oxidations with various reagents gave the corresponding 4,5‐dihydro‐1H‐imidazol‐5‐ones 2a, 2b, 2c, 2d, 2e, 2f, 2g: Pd/C (72–93%), DDQ (25–80%), and MnO2 (30–77%). Structure of the prepared compounds 1a, 1b, 1c, 1d, 1e, 1f, 1g and 2a, 2b, 2c, 2d, 2e, 2f, 2g was verified by 1H NMR and 13C NMR spectroscopy, EI‐MS and elemental analysis. X‐ray diffraction was performed in the case of compounds 1e and 2e. J. Heterocyclic Chem., (2010).
ABSTRACT (Chemical Equation Presented) A new method for the synthesis of substituted 5-(2-hydroxy... more ABSTRACT (Chemical Equation Presented) A new method for the synthesis of substituted 5-(2-hydroxyethyl)-2-phenylimino-1,3-thiazolidin-4-ones and 5-(2-hydroxyethyl)-2-phenylamino-4,5-dihydro-1,3-thiazol-4-ones is described, starting from phenylthioureas and 3-bromotetrahydrofuran-2-one. The reaction proceeds under mild conditions, is very simple to perform, and is applicable to a relatively wide range of substituents in benzene nucleus. Some 1,3-thiazolidin-4-ones show dynamic NMR behavior in solution because of prototropy tautomerism and E-/Z-stereoisomerism.
Collection of Czechoslovak Chemical Communications, 1989
The intramolecular nucleophilic addition of N-methyl-N-(2,4,6-trinitrophenyl)glycine anion in met... more The intramolecular nucleophilic addition of N-methyl-N-(2,4,6-trinitrophenyl)glycine anion in methanol-dimethyl sulfoxide mixtures produces spiro[(3-methyl-5-oxazolidinone)-2,1'-(2',4',6'-trinitrobenzenide)]. The spiro adduct has been identified by means of 1H and 13C NMR spectroscopy. This is the first case when the formation of a Meisenheimer adduct with carboxylate ion is observed. Logarithm of the equilibrium constant of adduct formation increases linearly with the mole fraction of dimethyl sulfoxide in its mixture with methanol.
A complex derived from the enantiomeric bipiperidine and copper(II) acetate hydrate is an efficie... more A complex derived from the enantiomeric bipiperidine and copper(II) acetate hydrate is an efficient catalyst for the enantioselective Henry reaction. The easy availability of both catalyst components, mild reaction conditions, high yield, and good to excellent enantioselectivity make the catalyst useful for everyday practice.
The Henry reaction was catalyzed by 0.01 equiv of aminopropylated nanosilica particles (nano-NAP)... more The Henry reaction was catalyzed by 0.01 equiv of aminopropylated nanosilica particles (nano-NAP) in refluxing nitroalkanes to provide nitrostyrenes in good yields. The catalyst could be recycled up to three times in 76% average yield.
Kinetic evidence has indicated that methanolysis of synthesized 4-acetoxybenzyl carbamates procee... more Kinetic evidence has indicated that methanolysis of synthesized 4-acetoxybenzyl carbamates proceeds via a one-step (concerted) mechanism. Concerted 1,6-elimination produces the very reactive 1,4-quinonemethide, which was trapped in the form of 4-methoxymethylphenol. The inhibition activity of benzyl N-phenylcarbamates to acetylcholinesterase (ACHE) and butyrylcholinesterase (BCHE) was also tested. The found IC 50 values varied within the limits of 199-535 µmol•l -1 for ACHE and 21-177 µmol•l -1 for BCHE. The found values of partition coefficient (P ow ) in the range of 1.5-11.5 represent a prerequisite of good transport of benzyl Nphenylcarbamates through haemato-encephalic barrier.
The synthesis of a water soluble azo initiators from 2,2'-azodiisobutyronitrile (AIBN) was perfor... more The synthesis of a water soluble azo initiators from 2,2'-azodiisobutyronitrile (AIBN) was performed in three steps: reaction of dinitrile with aromatic alcohols in the presence of HCl to form bisiminoesters hydrochlorides which are hydrolyzed to the esters and final regioselective sulfonation of the aromatic esters. The thermal decomposition of the azo initiators obtained leads to formation of two surface active radicals which can start the chain reaction.
The human drugs – antibiotic Linezolid (1) and anticoagulant Rivaroxaban (2) – belongs among mode... more The human drugs – antibiotic Linezolid (1) and anticoagulant Rivaroxaban (2) – belongs among modern pharmaceutics, which contain oxazolidine-2-one moiety bearing stereogenic centre. The chirality of these drugs is fundamental attribute of their biological activity. Herein, one of the efficient asymmetric syntheses of those drugs was studied in detail. High enantioselective catalysts were tested in the key step of the synthetic procedure, i.e. asymmetric Henry reaction, under different reaction conditions, using several starting aldehydes. The corresponding nitroaldols as chiral intermediates of those drugs were obtained in high yields and enantiomeric excess up to 91% ee.
A family of oxazaborines, diazaborinones, triazaborines, and triazaborinones was prepared by reac... more A family of oxazaborines, diazaborinones, triazaborines, and triazaborinones was prepared by reaction of polarized ethylenes, such as β-enaminoamides, with 4-methylbenzenediazonium tetraphenylborates. The reaction conditions (stirring in CH2Cl2 at room temperature (Method A) or stirring with CH3COONa in CH2Cl2 at room temperature (Method B) or refluxing in the CH2Cl2/toluene mixture (Method C)) controlled the formation and relative content of these compounds in the reaction mixtures from one to three products. Substituted oxazaborines gradually rearranged into diazaborinones at 250 °C. The prepared compounds were characterized by 1H NMR, 13C NMR, IR, and UV–Vis spectroscopy, HRMS, or microanalysis. The structure of individual compounds was confirmed by 11B NMR, 15N NMR, 1D NOESY, and X-ray analysis. The mechanism of reaction of enaminoamides with 4-methylbenzenediazonium tetraphenylborate was proposed.
The transition metal (palladium)-catalysed asymmetric 1,4-addition of arylboronic acids to conjug... more The transition metal (palladium)-catalysed asymmetric 1,4-addition of arylboronic acids to conjugated enones belong to the most important and emerging strategies for the construction of C–C bonds in an asymmetric fashion. This review covers known catalytic systems used for this transformation. For clarity, we are using the type of ligand as a sorting criterion. Finally, we attempted to create a flowchart facilitating the selection of a suitable ligand for a given combination of enone and arylboronic acid.
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Papers by Miloš Sedlák