Roman Mazurkiewicz - Academia.edu (original) (raw)
Papers by Roman Mazurkiewicz
Beilstein Journal of Organic Chemistry, 2015
A convenient approach has been developed to α-aminoalkylidenebisphosphonates and their asymmetric... more A convenient approach has been developed to α-aminoalkylidenebisphosphonates and their asymmetric phosphonyl-phosphinyl and phosphonyl-phosphinoyl analogues by α-phosphonylation, α-phosphinylation or α-phosphinoylation of 1-(N-acylamino)alkylphosphonates, that, in turn, are easily accessible from N-acyl-α-amino acids. Effective electrophilic activation of the α-position of 1-(Nacetylamino)alkylphosphonates was achieved by electrochemical α-methoxylation of these compounds in methanol, mediated with NaCl, followed by displacement of the methoxy group with triphenylphosphonium tetrafluoroborate to give hitherto unknown 1-(Nacetylamino)-1-triphenylphosphoniumalkylphosphonate tetrafluoroborates. The latter compounds react smoothly with trialkyl phosphites, dialkyl phosphonites or alkyl phosphinites in the presence of Hünig's base and methyltriphenylphosphonium iodide in a Michaelis-Arbuzov-like reaction to give the expected alkylidenebisphosphonates, 1-phosphinylalkylphosphonates or 1-phosphinoylalkylphosphonates, respectively, in good yields.
Organic Process Research & Development, 2006
... This article references 24 other publications. (1) Weissermel, K.; Arpe, HJ Industrial Organi... more ... This article references 24 other publications. (1) Weissermel, K.; Arpe, HJ Industrial Organic Chemistry; VCH Verlagsgesellschaft: Weinheim, 1993; p 328. (2) Boyaci, FG; Takac, S.; Calik, G.; Özdamar, TH Appl. Catal. ... J.; Tecza, W.; Machowska, ZUS Patent 6,107,527, 2000. ...
![Research paper thumbnail of Erratum to “Synthesis and properties of β-(N-acylamino)vinylphosphonium salts. A novel intramolecular [1,3] O-to-N migration of the vinyl group”](https://attachments.academia-assets.com/42132390/thumbnails/1.jpg)
](Tetrahedron Letters, 2002
Erratum to ''Synthesis and properties of b-(N-acylamino)vinylphosphonium salts. A novel intramole... more Erratum to ''Synthesis and properties of b-(N-acylamino)vinylphosphonium salts. A novel intramolecular [1,3] O-to-N migration of the vinyl group'' † PII of original article: S 0 0 4 0 -4 0 3 9 ( 0 1 ) 0 1 8 9 2 -5 0040-4039/02/$ -see front matter
![Research paper thumbnail of Synthesis and properties of β-(N-acylamino)vinylphosphonium salts. A novel intramolecular [1,3] O-to-N migration of the vinyl group](https://attachments.academia-assets.com/42132385/thumbnails/1.jpg)
](Tetrahedron Letters, 2001
A reaction of b-carbonyl phosphorus ylides with imidoyl halides gives hitherto unknown b-(Nacylam... more A reaction of b-carbonyl phosphorus ylides with imidoyl halides gives hitherto unknown b-(Nacylamino)vinylphosphonium salts. The key step of the reaction probably involves an intramolecular [1,3] O-to-N migration of the vinyl group, converting the primary O-imidoylation product into a b-(N-acylamino)vinylphosphonium salt.
ChemInform, 2009
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Journal of Molecular Structure: THEOCHEM, 2006
The rearrangements of free radicals originated from 2-(2-naphthyl)-1-methylethylhydroperoxide and... more The rearrangements of free radicals originated from 2-(2-naphthyl)-1-methylethylhydroperoxide and 2-(1-naphthyl)-1-methylethylhydroperoxide, i.e. from the molecules involved in the process of production of 2-naphthol from 2-isopropylnaphthalene, were investigated using theoretical methods (DFT). Moreover, the study was aimed at finding origins of inhibition of the process of 2-isopropenyloxynapthalene oxidation due to the contamination of raw material with 1-isopropylnaphthalene (1-IPN). It has been found that one of the reaction paths involving the rearrangement of a free radical originated from 1-IPN can be responsible for the process of inhibition. q
The synthesis of , -dehydro--aminophosphonic and , -dehydro--aminophosphinic acid derivatives is ... more The synthesis of , -dehydro--aminophosphonic and , -dehydro--aminophosphinic acid derivatives is discussed. The most important synthetic pathways to the above-mentioned compounds have been divided into four groups depending on the type of bond formed as the last one. The configuration at the C=C double bond can be established based on the specific coupling constants 3 JHP and 3 JCP for the appropriate Z-and E-stereoisomers. The application of , -dehydro--aminophosphonates and , -dehydro-aminophosphinates, particularly in the enantioselective catalytic hydrogenation, is also discussed.
Thermochimica Acta, 2011
... numerous applications in organic synthesis [4]. 2. Experimental. 2.1. General. Melting points... more ... numerous applications in organic synthesis [4]. 2. Experimental. 2.1. General. Melting points are uncorrected and were determined in capillary tubes using a Stuart Scientific SMP3 melting point apparatus. 1 H and 13 C NMR ...
Tetrahedron Letters, 2006
ABSTRACT Easily accessible N-acyl-2-triphenylphosphonioglycinate tetrafluoroborates react smoothl... more ABSTRACT Easily accessible N-acyl-2-triphenylphosphonioglycinate tetrafluoroborates react smoothly with trimethylphosphite in the presence of methyltriphenylphosphonium iodide to give N-acyl-2-(dimethoxyphosphoryl)glycinates in good or very good yields. The dimethoxyphosphorylglycinates may be isolated by column chromatography, or used directly for the Wadsworth-Emmons synthesis of alpha,beta-dehydro-alpha-amino acids in a one-pot procedure without purification. (c) 2006 Elsevier Ltd. All rights reserved.
Tetrahedron Letters, 2009
ABSTRACT 1-(N-Acylaminoalkyl)triphenylphosphonium salts 2a–f on reaction with DBU in MeCN are tra... more ABSTRACT 1-(N-Acylaminoalkyl)triphenylphosphonium salts 2a–f on reaction with DBU in MeCN are transformed into 1-(N-acylaminoalkyl)amidinium salts 3a–f. Amidinium salts 3d–f with a proton at the β-position undergo slow tautomerization into the corresponding enamides 6d–f. The same 1-(N-acylamino)alkyltriphenylphosphonium salts 2d–f in the presence of Hünig’s base are transformed directly into the corresponding enamides. Phosphonium salts 2, amidinium salts 3, and enamides 6 react with dialkyl malonates in the presence of DBU to give the corresponding amidoalkylation products. α-Amidoalkylation of dialkyl malonates is not observed in the presence of (i-Pr)2EtN, yet proceeds well under these conditions with more acidic nucleophiles, for example, phthalimide or benzyl mercaptan.
Monatshefte für Chemie - Chemical Monthly, 2009
Thermal decomposition of 1-methyl-1-(4methyl-1-naphthyl)ethyl hydroperoxide under gas chromatogra... more Thermal decomposition of 1-methyl-1-(4methyl-1-naphthyl)ethyl hydroperoxide under gas chromatography-mass spectroscopy (GC-MS) conditions gives 2-((4-methyl-1-naphthyl)oxy)propene as the main product (50.5%), without any detectable traces of the isomeric 2-((5-methyl-1-naphthyl)oxy)propene. This finding excludes the rearrangement pathway of 1-methyl-1-(1-naphthyl)ethyl hydroperoxides to the corresponding 2-(1-naphthyloxy) propenes, which involves formation of a naphthofuran derivative as an intermediate and transfer of the isopropenyloxy group to the 8 position. This result, as well as our previous density functional theory (DFT) calculations, points to the rearrangement pathway involving an oxirane-type intermediate as the most plausible pathway to 2-(1-naphthyloxy)propenes. This rearrangement is responsible for the unusual inhibition effects of 1-methyl-1-(1-naphthyl)ethyl hydroperoxide on the liquid-phase oxidation of isopropylarenes with oxygen.
Monatshefte für Chemie/Chemical Monthly, 2004
N-Acyl--triphenylphosphonioglycinates when treated with triethylamine are transformed to an equil... more N-Acyl--triphenylphosphonioglycinates when treated with triethylamine are transformed to an equilibrium mixture of the corresponding N-acyliminoacetates and N-acyl--triphenylphosphoranylideneglycinates. Wittig reaction of the latter ylides with aromatic and aliphatic aldehydes or ketones enables a new easy entry to N-acyl-,-dehydro--amino acid esters.
Monatshefte für Chemie/Chemical Monthly, 2004
ABSTRACT N-Acyl-a-hydroxyglycinates were transformed into N-acyl-a-triphenylphosphonioglycinates ... more ABSTRACT N-Acyl-a-hydroxyglycinates were transformed into N-acyl-a-triphenylphosphonioglycinates by ( i) phosphorylation with Ph 3PBr 2 in the presence of Et 3N or ( ii) in reaction with DCC and Ph 3P·HBF 4 in the presence of catalytic amounts of Ph 3P as well as ( iii) by a new kind of Mitsunobu reaction with Ph 3P·HBF 4 as a nucleophile conjugated acid. The N-acyl-a-triphenylphosphonioglycinates can be effectively used without isolation for a nucleophilic displacement of the triphenylphosphonium group to obtain corresponding a-substituted a-amino acid derivatives.
Monatshefte für Chemie - Chemical Monthly, 2010
Oxidation of cumene with 1-methyl-1-phenylethyl hydroperoxide in the presence of copper chloride/... more Oxidation of cumene with 1-methyl-1-phenylethyl hydroperoxide in the presence of copper chloride/ phase transfer catalytic systems was investigated by ESI-MS. For catalytically active copper(II) chloride/crown ethers, copper(II) chloride/crown ethers/alkaline metal salts, and copper(II) chloride/tetrabutylammonium chloride systems, the presence of a few kinds of copper complexes in the organic phase was detected by use of ESI-MS. When copper(II) chloride/podand systems were used, the conversion of hydroperoxide and the yield of oxidation product were close to zero, although the concentration of copper complexes in the organic phase was high. Addition of bis(2-hydroxyethyl) ether to the catalytically active copper(II) chloride/18-crown-6 system resulted in an inhibition effect.
Magnetic Resonance in Chemistry, 2005
The diagnostic values of the following three spectral criteria for the configuration of N-acyl-al... more The diagnostic values of the following three spectral criteria for the configuration of N-acyl-alpha,beta-dehydro-alpha-amino acid esters were examined: (i) the proton at the beta-position at the double bond of a Z-isomer is shielded if compared with the respective E-isomer (delta(beta)Z < delta(beta)E); (ii) the proton at the nitrogen atom is shielded in a Z-isomer in comparison with the corresponding E-isomer (delta(NH)Z < delta(NH)E); and (iii) changing of the solvent from CDCl3 to deuterated trifluoroacetic acid (TFA) causes shielding of the H(beta) vinylic proton of an E-isomer or deshielding of the respective proton of the Z-isomer (delta(CDCl3)E > delta(TFA)E or delta(CDCl3)Z < delta(TFA)Z). The investigations were based on a set of 22 (Z)- and (E)-N-acyl-alpha,beta-dehydro-alpha-amino acid esters of diverse structures, with aliphatic, aromatic and heteroaromatic substituents at the vinylic beta-carbon; most of the examined compounds were hitherto unknown. The application of the substituent effect additivity rule given by Pascual et al. for olefinic protons leads to evidently erroneous configuration assignments of N-acyl-alpha,beta-dehydro-alpha-amino acid esters. The considered criteria were fulfilled for all the examined cases with one exception [the second criterion for the alpha-pivaloylamino-beta-(2-furyl)acrylates]. The comparison of changes in the chemical shifts of H(beta) vinylic protons in CDCl3 and deuterated TFA seems to be the most reliable and useful configuration criterion, as it can be used in the case of a single isomer.
Applied Catalysis A: General, 2001
Symmetrical and unsymmetrical peroxides can be obtained by the oxidation of isopropyl arenes with... more Symmetrical and unsymmetrical peroxides can be obtained by the oxidation of isopropyl arenes with tertiary hydroperoxides in the presence of copper salt-crown ether as catalysts. The efficiency of the investigated catalytic system enhances markedly in the presence of some alkali metal salts, with a cation diameter corresponding to the inner diameter of the crown ether. The oxidation of isopropyl arenes with hydroperoxides in the presence of a copper salt-crown ether-alkali metal salt catalytic system proved to be a simple and efficient method for the synthesis of ditertiary peroxides. A possible mechanism of this phenomenon is discussed. The results obtained confirm strongly that phase transfer catalysis operates in the investigated reaction.
Tetrahedron: Asymmetry, 2011
3-Triphenylphosphonio-2,5-piperazinediones were effectively synthesized from homochiral valine or... more 3-Triphenylphosphonio-2,5-piperazinediones were effectively synthesized from homochiral valine or proline via Boc-Val-Gly-OMe, Boc-Pro-Gly-OMe or Cbz-Pro-Gly-OMe. Retention of configuration of the primary stereogenic center of the valine and proline moieties was observed. Diastereoselective nucleophilic substitution of the triphenylphosphonium group in 2,5-piperazinediones with S-, N-, P- and C-nucleophiles was observed. The configuration of the substitution products was assigned either by their hydrolysis and
Beilstein Journal of Organic Chemistry, 2015
A convenient approach has been developed to α-aminoalkylidenebisphosphonates and their asymmetric... more A convenient approach has been developed to α-aminoalkylidenebisphosphonates and their asymmetric phosphonyl-phosphinyl and phosphonyl-phosphinoyl analogues by α-phosphonylation, α-phosphinylation or α-phosphinoylation of 1-(N-acylamino)alkylphosphonates, that, in turn, are easily accessible from N-acyl-α-amino acids. Effective electrophilic activation of the α-position of 1-(Nacetylamino)alkylphosphonates was achieved by electrochemical α-methoxylation of these compounds in methanol, mediated with NaCl, followed by displacement of the methoxy group with triphenylphosphonium tetrafluoroborate to give hitherto unknown 1-(Nacetylamino)-1-triphenylphosphoniumalkylphosphonate tetrafluoroborates. The latter compounds react smoothly with trialkyl phosphites, dialkyl phosphonites or alkyl phosphinites in the presence of Hünig's base and methyltriphenylphosphonium iodide in a Michaelis-Arbuzov-like reaction to give the expected alkylidenebisphosphonates, 1-phosphinylalkylphosphonates or 1-phosphinoylalkylphosphonates, respectively, in good yields.
Organic Process Research & Development, 2006
... This article references 24 other publications. (1) Weissermel, K.; Arpe, HJ Industrial Organi... more ... This article references 24 other publications. (1) Weissermel, K.; Arpe, HJ Industrial Organic Chemistry; VCH Verlagsgesellschaft: Weinheim, 1993; p 328. (2) Boyaci, FG; Takac, S.; Calik, G.; Özdamar, TH Appl. Catal. ... J.; Tecza, W.; Machowska, ZUS Patent 6,107,527, 2000. ...
Tetrahedron Letters, 2002
Erratum to ''Synthesis and properties of b-(N-acylamino)vinylphosphonium salts. A novel intramole... more Erratum to ''Synthesis and properties of b-(N-acylamino)vinylphosphonium salts. A novel intramolecular [1,3] O-to-N migration of the vinyl group'' † PII of original article: S 0 0 4 0 -4 0 3 9 ( 0 1 ) 0 1 8 9 2 -5 0040-4039/02/$ -see front matter
Tetrahedron Letters, 2001
A reaction of b-carbonyl phosphorus ylides with imidoyl halides gives hitherto unknown b-(Nacylam... more A reaction of b-carbonyl phosphorus ylides with imidoyl halides gives hitherto unknown b-(Nacylamino)vinylphosphonium salts. The key step of the reaction probably involves an intramolecular [1,3] O-to-N migration of the vinyl group, converting the primary O-imidoylation product into a b-(N-acylamino)vinylphosphonium salt.
ChemInform, 2009
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Journal of Molecular Structure: THEOCHEM, 2006
The rearrangements of free radicals originated from 2-(2-naphthyl)-1-methylethylhydroperoxide and... more The rearrangements of free radicals originated from 2-(2-naphthyl)-1-methylethylhydroperoxide and 2-(1-naphthyl)-1-methylethylhydroperoxide, i.e. from the molecules involved in the process of production of 2-naphthol from 2-isopropylnaphthalene, were investigated using theoretical methods (DFT). Moreover, the study was aimed at finding origins of inhibition of the process of 2-isopropenyloxynapthalene oxidation due to the contamination of raw material with 1-isopropylnaphthalene (1-IPN). It has been found that one of the reaction paths involving the rearrangement of a free radical originated from 1-IPN can be responsible for the process of inhibition. q
The synthesis of , -dehydro--aminophosphonic and , -dehydro--aminophosphinic acid derivatives is ... more The synthesis of , -dehydro--aminophosphonic and , -dehydro--aminophosphinic acid derivatives is discussed. The most important synthetic pathways to the above-mentioned compounds have been divided into four groups depending on the type of bond formed as the last one. The configuration at the C=C double bond can be established based on the specific coupling constants 3 JHP and 3 JCP for the appropriate Z-and E-stereoisomers. The application of , -dehydro--aminophosphonates and , -dehydro-aminophosphinates, particularly in the enantioselective catalytic hydrogenation, is also discussed.
Thermochimica Acta, 2011
... numerous applications in organic synthesis [4]. 2. Experimental. 2.1. General. Melting points... more ... numerous applications in organic synthesis [4]. 2. Experimental. 2.1. General. Melting points are uncorrected and were determined in capillary tubes using a Stuart Scientific SMP3 melting point apparatus. 1 H and 13 C NMR ...
Tetrahedron Letters, 2006
ABSTRACT Easily accessible N-acyl-2-triphenylphosphonioglycinate tetrafluoroborates react smoothl... more ABSTRACT Easily accessible N-acyl-2-triphenylphosphonioglycinate tetrafluoroborates react smoothly with trimethylphosphite in the presence of methyltriphenylphosphonium iodide to give N-acyl-2-(dimethoxyphosphoryl)glycinates in good or very good yields. The dimethoxyphosphorylglycinates may be isolated by column chromatography, or used directly for the Wadsworth-Emmons synthesis of alpha,beta-dehydro-alpha-amino acids in a one-pot procedure without purification. (c) 2006 Elsevier Ltd. All rights reserved.
Tetrahedron Letters, 2009
ABSTRACT 1-(N-Acylaminoalkyl)triphenylphosphonium salts 2a–f on reaction with DBU in MeCN are tra... more ABSTRACT 1-(N-Acylaminoalkyl)triphenylphosphonium salts 2a–f on reaction with DBU in MeCN are transformed into 1-(N-acylaminoalkyl)amidinium salts 3a–f. Amidinium salts 3d–f with a proton at the β-position undergo slow tautomerization into the corresponding enamides 6d–f. The same 1-(N-acylamino)alkyltriphenylphosphonium salts 2d–f in the presence of Hünig’s base are transformed directly into the corresponding enamides. Phosphonium salts 2, amidinium salts 3, and enamides 6 react with dialkyl malonates in the presence of DBU to give the corresponding amidoalkylation products. α-Amidoalkylation of dialkyl malonates is not observed in the presence of (i-Pr)2EtN, yet proceeds well under these conditions with more acidic nucleophiles, for example, phthalimide or benzyl mercaptan.
Monatshefte für Chemie - Chemical Monthly, 2009
Thermal decomposition of 1-methyl-1-(4methyl-1-naphthyl)ethyl hydroperoxide under gas chromatogra... more Thermal decomposition of 1-methyl-1-(4methyl-1-naphthyl)ethyl hydroperoxide under gas chromatography-mass spectroscopy (GC-MS) conditions gives 2-((4-methyl-1-naphthyl)oxy)propene as the main product (50.5%), without any detectable traces of the isomeric 2-((5-methyl-1-naphthyl)oxy)propene. This finding excludes the rearrangement pathway of 1-methyl-1-(1-naphthyl)ethyl hydroperoxides to the corresponding 2-(1-naphthyloxy) propenes, which involves formation of a naphthofuran derivative as an intermediate and transfer of the isopropenyloxy group to the 8 position. This result, as well as our previous density functional theory (DFT) calculations, points to the rearrangement pathway involving an oxirane-type intermediate as the most plausible pathway to 2-(1-naphthyloxy)propenes. This rearrangement is responsible for the unusual inhibition effects of 1-methyl-1-(1-naphthyl)ethyl hydroperoxide on the liquid-phase oxidation of isopropylarenes with oxygen.
Monatshefte für Chemie/Chemical Monthly, 2004
N-Acyl--triphenylphosphonioglycinates when treated with triethylamine are transformed to an equil... more N-Acyl--triphenylphosphonioglycinates when treated with triethylamine are transformed to an equilibrium mixture of the corresponding N-acyliminoacetates and N-acyl--triphenylphosphoranylideneglycinates. Wittig reaction of the latter ylides with aromatic and aliphatic aldehydes or ketones enables a new easy entry to N-acyl-,-dehydro--amino acid esters.
Monatshefte für Chemie/Chemical Monthly, 2004
ABSTRACT N-Acyl-a-hydroxyglycinates were transformed into N-acyl-a-triphenylphosphonioglycinates ... more ABSTRACT N-Acyl-a-hydroxyglycinates were transformed into N-acyl-a-triphenylphosphonioglycinates by ( i) phosphorylation with Ph 3PBr 2 in the presence of Et 3N or ( ii) in reaction with DCC and Ph 3P·HBF 4 in the presence of catalytic amounts of Ph 3P as well as ( iii) by a new kind of Mitsunobu reaction with Ph 3P·HBF 4 as a nucleophile conjugated acid. The N-acyl-a-triphenylphosphonioglycinates can be effectively used without isolation for a nucleophilic displacement of the triphenylphosphonium group to obtain corresponding a-substituted a-amino acid derivatives.
Monatshefte für Chemie - Chemical Monthly, 2010
Oxidation of cumene with 1-methyl-1-phenylethyl hydroperoxide in the presence of copper chloride/... more Oxidation of cumene with 1-methyl-1-phenylethyl hydroperoxide in the presence of copper chloride/ phase transfer catalytic systems was investigated by ESI-MS. For catalytically active copper(II) chloride/crown ethers, copper(II) chloride/crown ethers/alkaline metal salts, and copper(II) chloride/tetrabutylammonium chloride systems, the presence of a few kinds of copper complexes in the organic phase was detected by use of ESI-MS. When copper(II) chloride/podand systems were used, the conversion of hydroperoxide and the yield of oxidation product were close to zero, although the concentration of copper complexes in the organic phase was high. Addition of bis(2-hydroxyethyl) ether to the catalytically active copper(II) chloride/18-crown-6 system resulted in an inhibition effect.
Magnetic Resonance in Chemistry, 2005
The diagnostic values of the following three spectral criteria for the configuration of N-acyl-al... more The diagnostic values of the following three spectral criteria for the configuration of N-acyl-alpha,beta-dehydro-alpha-amino acid esters were examined: (i) the proton at the beta-position at the double bond of a Z-isomer is shielded if compared with the respective E-isomer (delta(beta)Z < delta(beta)E); (ii) the proton at the nitrogen atom is shielded in a Z-isomer in comparison with the corresponding E-isomer (delta(NH)Z < delta(NH)E); and (iii) changing of the solvent from CDCl3 to deuterated trifluoroacetic acid (TFA) causes shielding of the H(beta) vinylic proton of an E-isomer or deshielding of the respective proton of the Z-isomer (delta(CDCl3)E > delta(TFA)E or delta(CDCl3)Z < delta(TFA)Z). The investigations were based on a set of 22 (Z)- and (E)-N-acyl-alpha,beta-dehydro-alpha-amino acid esters of diverse structures, with aliphatic, aromatic and heteroaromatic substituents at the vinylic beta-carbon; most of the examined compounds were hitherto unknown. The application of the substituent effect additivity rule given by Pascual et al. for olefinic protons leads to evidently erroneous configuration assignments of N-acyl-alpha,beta-dehydro-alpha-amino acid esters. The considered criteria were fulfilled for all the examined cases with one exception [the second criterion for the alpha-pivaloylamino-beta-(2-furyl)acrylates]. The comparison of changes in the chemical shifts of H(beta) vinylic protons in CDCl3 and deuterated TFA seems to be the most reliable and useful configuration criterion, as it can be used in the case of a single isomer.
Applied Catalysis A: General, 2001
Symmetrical and unsymmetrical peroxides can be obtained by the oxidation of isopropyl arenes with... more Symmetrical and unsymmetrical peroxides can be obtained by the oxidation of isopropyl arenes with tertiary hydroperoxides in the presence of copper salt-crown ether as catalysts. The efficiency of the investigated catalytic system enhances markedly in the presence of some alkali metal salts, with a cation diameter corresponding to the inner diameter of the crown ether. The oxidation of isopropyl arenes with hydroperoxides in the presence of a copper salt-crown ether-alkali metal salt catalytic system proved to be a simple and efficient method for the synthesis of ditertiary peroxides. A possible mechanism of this phenomenon is discussed. The results obtained confirm strongly that phase transfer catalysis operates in the investigated reaction.
Tetrahedron: Asymmetry, 2011
3-Triphenylphosphonio-2,5-piperazinediones were effectively synthesized from homochiral valine or... more 3-Triphenylphosphonio-2,5-piperazinediones were effectively synthesized from homochiral valine or proline via Boc-Val-Gly-OMe, Boc-Pro-Gly-OMe or Cbz-Pro-Gly-OMe. Retention of configuration of the primary stereogenic center of the valine and proline moieties was observed. Diastereoselective nucleophilic substitution of the triphenylphosphonium group in 2,5-piperazinediones with S-, N-, P- and C-nucleophiles was observed. The configuration of the substitution products was assigned either by their hydrolysis and