Clifford C. Leznoff

York University, Toronto, Ontario, Canada

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Publications (105)150.57 Total impact

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    Dataset: LEZ112
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    Dataset: LEZ105
    Hiroaki Isago, Dmitri S. Terekhov, Clifford C. Leznoff
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    Dataset: LEZ105
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    Dataset: LEZ112
  • Hiroakiisago, Dmitri S.terekhov, Clifford C.leznoff
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    ABSTRACT: By a mixed condensation of 1,3-bis(3″,4″-dicyanophenoxy)-2-ethyl-2-methylpropane with a large amount of 4,5-bis(3,3-dimethyl-1-butynyl)phthalonitrile, 1,3-bis-2″-(9″,10″,16″,17″,23″,24″-hexakis(3″,3″-dimethyl-1″-butynyl)phthalocyaninoxyl)-2-ethyl-2-methylpropane, was synthesized as a binuclear phthalocyanine having a single isomer. NMR studies at various temperatures and concentrations suggested that the interactions between the phthalocyanine macrocycles were dominated by intermolecular aggregation at lower temperatures or high concentrations whereas intramolecular aggregation was predominant at higher temperatures or lower concentrations.
    Journal of Porphyrins and Phthalocyanines 04/2012; 01(02). · 1.43 Impact Factor
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    ABSTRACT: Coupling of 4,5-diiodophthalonitrile with tert-butyldimethylsilylacetylene and a palladium catalyst gave 4,5-bis(tert-butyldimethylsilylethynyl)phthalonitrile. Cleavage of the silyl moiety with tetrabutylammonium fluoride gave 4,5-diethynylphthalonitrile, while condensation in 2-N,N-dimethylaminoethanol without or with Zn(OAc)2 gave metal-free 2,3,8,9,16,17,23,24-octakis(tert-butyldimethylsilylethynyl)phthalocyanine or its zinc derivative. Cleavage of the silyl groups of the zinc derivative gave an insoluble product whose 1H NMR spectrum was indicative of 2,3,9,10,16,17,23,24-octaethynylphthalocyaninato zinc(II). Bromination of phthalonitrile with N,N-dibromoisocyanuric acid gave a separable mixture of 3,6-, 3,4- and 4,5-dibromophthalonitrile along with the monobromophthalonitriles. Coupling of 3,4-dibromophalonitrile with tert-butylacetylene gave 3,4-bis(tert-butylethynyl)phthalonitrile, which on condensation with lithium 1-pentanolate gave 1,2,8,9,15,16,22,23-octakis(3,3-dimethyl-1-butynyl)phthalocyanine as a single isomer, the first known 1,2,8,9,15,16,22,23-octasubstituted phthalocyanine.
    Journal of Porphyrins and Phthalocyanines 04/2012; 03(06). · 1.43 Impact Factor
  • Clifford C.leznoff, Anna M.d'ascanio, S. Zekiyildiz
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    ABSTRACT: Lithium metal added to a solution of 4-neopentoxyphthalonitrile in 1-octanol or other long-chain primary alcohols at room temperature resulted in phthalocyanine formation at a reasonable rate in good yield, while preformed lithium 1-octanolate under the same conditions gave 2,9,16,23-tetraneopentoxyphthalocyanine, but in lower yield at a slower rate. The use of lower-molecular-weight alcohols slowly gave a phthalocyanine in lower yields. Reverse micelle formation when using long-chain alcohols is proposed as a possibility for enhanced phthalocyanine formation at room temperature. 2,9,16,23-Tetrasubstituted phthalocyanines and metallated phthalocyanines were prepared at room temperature from 4-neopentoxyphthalonitrile, 4-bis(4-methoxyphenyl)methoxyphthalonitrile, 4-[1-(4-ethoxy-3-methoxyphenyl)-1-phenyl]methoxyphthalonitrile and phthalonitrile using lithium 1-octanolate in 1-octanol or by the addition, to a solution of the phthalonitrile in ethanol, of calcium turnings or, to a solution of the phthalonitrile in methanol, of magnesium, zinc, iron or copper powder. The tetrasubstituted phthalocyanines produced exhibited a non-statistical distribution of regioisomers, indicating that electronic effects become important in room-temperature cyclotetramerization of phthalonitriles to phthalocyanines.
    Journal of Porphyrins and Phthalocyanines 04/2012; 04(01). · 1.43 Impact Factor
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    Clifford C. Leznoff, Colin R. McArthur, Mark Whittaker
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    ABSTRACT: The key chiral synthons, (R)-3-isopropenyl-6-heptenoic acid and (R)-3-isopropenyl-6-heptenal, needed for the synthesis of (3Z,6R)-3-methyl-6-isopropenyl-3,9-decadien-1-yl acetate, a component of the sex pheromone of the California red scale, Aonidiellaaurantii, have been prepared by asymmetric synthesis. The chiral acid was synthesized in 86% ee by an asymmetric 1,4-addition of isopropenylmagnesium bromide to the l-ephedrine amide derived from (E)-2,6-heptadienoic acid, followed by base hydrolysis. Acid hydrolysis gave the chiral 3-(3-buten-1-yl)-4,4-dimethylbutyrolactone. The chiral aldehyde was prepared in greater than 99% ee by an asymmetric 1,4-addition of isopropenylmagnesium bromide to the imine derived from (S)-(+)-tert-butyl 2-amino-3,3-dimethylbutyrate and (E)-2,6-heptadienal. The 1,4-addition reactions of n-butyllithium or isopropenyllithium to (4S,5S)-(+)-2-[1-(E-1,5-hexadienyl)]-4-methoxymethyl-5-phenyl-2-oxazoline gave the addition products, and sequential mild hydrolysis and reduction of these adducts yielded chiral 3-n-butyl-6-hepten-1-ol for the former adduct but a mixture of products was obtained from the latter adduct.
    02/2011;
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    ABSTRACT: Hydrolysis of 5-neopentoxy-1,3-diiminoisoindoline gave 5-neopentoxy-1H-isoindole-1,3(2H)-dione (4-neopentoxyphthalimide), which, on treatment with Lawesson's reagent, yielded the thiophthalimides, 5-neopentoxy-1H-isoindole-1,3(2H)-dithione, 2,3-dihydro-6-neopentoxy-3-thioxo-1H-isoindol-1-one, and 2,3-dihydro-5-neopentoxy-3-thioxo-1H-isoindol-1-one. Attempted S-alkylations of the thiophthalimides resulted in the formation of β-isoindigos and N-alkylation products. In a new phthalocyanine synthesis crossed condensations of 1,3-diiminoisoindoline with 5-neopentoxy-1H-isoindole-1,3(2H)-dithione yielded mixtures of phthalocyanines from which 2-neopentoxyphthalocyanine and 2,16-dineopentoxyphthalocyanine could be purified in part from other phthalocyanines.
    Canadian Journal of Chemistry 02/2011; 65(8):1705-1713. · 0.96 Impact Factor
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    ABSTRACT: The spectral and electrochemical properties of tetrabenzo[5,10,15]triazaporphine (TBTAP) and its magnesium derivatives having a long alkyl chain attached to the meso carbon have been studied. Both metal-free and metallated species show typical metal-free phthalocyanine-like spectra. Two reduction and two oxidation redox couples have been observed. The cation, anion, and dianion species of these porphyrin derivatives have been electrochemically generated and their electronic spectra are recorded.
    Canadian Journal of Chemistry 02/2011; 71(5):742-753. · 0.96 Impact Factor
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    ABSTRACT: 2,9,16,23-Tetra-p-n-butylbenzyloxy-, 2,9,16,23-tetradiphenylmethoxy-, 2,9,16,23-tetramethoxymethoxy-, and 1,8,15,22-tetra-p-n-butylbenzyloxyphthalocyanines were synthesized from the appropriate phthalonitriles. Metal-free phthalocyanines were converted to their zinc derivatives. Cleavage from the appropriate precursor with trifluoroacetic acid produced 2,9,16,23-tetrahydroxyphthalocyanine and 1,8,15,22-tetrahydroxyphthalocyanine and their zinc derivatives. NMR spectroscopy revealed that all the 2,9,16,23-tetrasubstituted phthalocyanines are the usual mixtures of the 2,9,16,23, 2,9,16,24, 2,9,17,24, and 2,10,16,24 isomers, but the two 1,8,15,22-tetrasubstituted phthalocyanines were formed as pure single isomers.
    Canadian Journal of Chemistry 02/2011; 72(9):1990-1998. · 0.96 Impact Factor
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    ABSTRACT: Electrophilic aromatic nitration under mild conditions of 4-hydroxyphthalonitrile gave 4-hydroxy-3-nitrophthalonitrile and 4-hydroxy-5-nitrophthalonitrile, while bromination yielded 3-bromo-4-hydroxyphthalonitrile, 4-bromo-5-hydroxyphthalonitrile, and 3,5-dibromo-4-hydroxyphthalonitrile. Iodination gave 4-hydroxy-5-iodophthalonitrile and 4-hydroxy-3,5-diidophthalonitrile. Coupling of 4-iodophthalonitrile, 3-iodophthalonitrile, and 5-iodo-2,3-dicyanonaphthalene with trans-1,2-bis(tri-n-butylstannyl)ethene gave trans-1,2-bis(3,4-dicyanophenyl)ethene, trans-1,2-bis(2,3-dicyanophenyl)ethene, and trans-1,2-bis(6,7-dicyanonaphthyl)ethene. Photocyclization of a dilute solution of cis- or trans-1,2-bis(3,4-dicyanophenyl)ethene in dioxane gave a 1:1 mixture of 2,3,6,7- and 2,3,5,6-tetracyanophenanthrenes separable by chromatography. Keywords: phthalonitriles, naphthalenedicarbonitriles, phenanthrenetetracarbonitriles, electrophilic substitution.
    ChemInform 02/2011;
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    ABSTRACT: Insoluble cross-linked copolymers of styrene and 1% divinylbenzene with covalently bonded (S)-2-aminoalkoxy groups were used in the enantioselective α-methylation of cyclohexanone through the corresponding imines. Enantiomeric excesses of 94% of (S)-2-methylcyclohexanone were observed on methylation at 20 °C. An analogous optically active 2-aminoalkyl benzyl ether, under otherwise identical conditions, resulted in a lower enantiomeric excess (49%) with selectivity approaching that of the polymer only at −78 °C.
    Canadian Journal of Chemistry 02/2011; 60(14):1836-1841. · 0.96 Impact Factor
  • Colin R. McArthur, Ji-Long Jiang, Clifford C. Leznoff
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    ABSTRACT: Asymmetric protonations, with enantioselectivities ranging to 90%, were observed in reactions of lithioenamines derived from imines of racemic 2-methylcyclohexanone and insoluble cross-linked copolymers of polystyrene and divinylbenzene substituted with (S)-2-aminoalkoxymethyl groups.
    Canadian Journal of Chemistry 02/2011; 60(23):2984-2985. · 0.96 Impact Factor
  • Zhang-Huang Xu, Colin R. McArthur, Clifford C. Leznoff
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    ABSTRACT: A 1% crosslinked divinylbenzene–styrene copolymer, incorporating vicinal diol groups or their isopropylidenc precursors, was used to form the monoacetals of the symmetrical diketones, p-diacetylbenzene, 1,2-cyclohexanedione, 1,3-cyclohexanedionc, 1,4-cyclohexanedione, and 2,5-hexanedione. The free ketone groups reacted with phenylmagnesium bromide to give, in high yield, after acid hydrolysis from the polymer, the expected products such as 3-phenyl-2-cyclohexen-1-one from 1,3-cyclohexanedione. The 13C nmr spectra of some polymer-bound substrates and simple analogs are described.
    Canadian Journal of Chemistry 02/2011; 61(7):1405-1409. · 0.96 Impact Factor
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    Clifford C. Leznoff, David M. Drew
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    ABSTRACT: Nucleophilic aromatic substitution reactions of 3-nitrophthalonitrile yield 3-hydroxyphthalonitrile and 3-neopentoxyphthalonitrile, the latter of which condensed to 1,8,15,22-tetraneopentoxyphthalocyanine as a mixture of isomers. Bisphthalonitriles such as 1,3-bis(2′,3′-dicyanophenoxy)-2,2-dipentylpropane, 1,3-bis(2′,3′-dicyanophenoxy)-2,2-diethylpropane, 1,3-bis(2′,3′-dicyanophenoxy)-2,2-dioctylpropane, and 1,3-bis(2′,3′-dicyanophenoxy)-2-methyl-2-trityloxymethylpropane all gave bis-crown-like 1,11,15,25-tetrasubstituted phthalocyanines as pure compounds when treated with lithium octoxide in 1-octanol at 196 °C. A host of nine other bisphthalonitriles including 1,5-bis(2′,3′-dicyanophenoxy)-3-oxapentane, 1,1-bis(2′,3′-dicyanophenoxymethyl)cyclohexane, 1,2-bis(2′,3′-dicyanophenoxymethyl)benzene, and 2,5-bis(2′,3′-dicyanophenoxymethyl)furan did not dimerize to mononuclear phthalocynaines. The "gem dimethyl" effect was suggested as a reason for the successful macrocyclizations. Key words: nucleophilic aromatic substitution, phthalonitriles, bisphthalonitriles, 1,11,15,25-tetrasubstituted phthalocyanines.
    Canadian Journal of Chemistry 02/2011; 74(3):307-318. · 0.96 Impact Factor
  • Patrick W Causey, Igor Dubovyk, Clifford C Leznoff
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    ABSTRACT: The reaction of 3,4,5,6-tetrafluorophthalonitrile with 1-adamantanol, 1-adamantylamine, 1-adamantanemethanol, and 1-adamantaneethanol gave 4,5-di-(1-adamantyloxy)-3,6-difluorophthalonitrile, 4,5-di-(1-adamantylamino)-3,6-difluorophthalonitrile, 4-(1-adamantylamino)-3,5,6-trifluorophthalonitrile, 3,4,5,6-tetra-(1-adamantylmethoxy)phthalonitrile, and 3,4,5,6-tetra-(1-adamantylethoxy)phthalonitrile, respectively. The conversion of these tetrasubstituted phthalonitriles to magnesium, nickel, and metal-free phthalocyanines was demonstrated. These highly hindered phthalocyanines exhibited interesting red shifts in their UV–vis spectra.Key words: highly hindered adamantane phthalocyanines, adamantylphthalonitriles.
    Canadian Journal of Chemistry 02/2011; 84(10):1380-1387. · 0.96 Impact Factor
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    Michael R. Hempstead, A. B. P. Lever, Clifford C. Leznoff
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    ABSTRACT: Investigations of the electrocatalytic activity of mononuclear and binuclear cobalt phthalocyanines for the reduction of molecular oxygen established that the latter compounds are more effective catalysts than the corresponding mononuclear species. A correlation between the half-band widths for the Q band of these species and their catalytic efficiency, expressed as a kinetically-limited current, suggests that the increase in activity may be attributed to electronic coupling between the phthalocyanine rings.
    Canadian Journal of Chemistry 02/2011; 65(11):2677-2684. · 0.96 Impact Factor
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    ABSTRACT: Metal-free copper and cobalt(II) binuclear phthalocyanines, in which the two phthalocyanine nuclci are covalently linked through five-atom bridges, have been prepared and characterized. Some new metal-free, copper, cobalt(II), and zinc 2,9,16,23-tetraalkoxyphthalocyanines, some of which are extremely soluble in organic solvents, are described.
    Canadian Journal of Chemistry 02/2011; 63(3):623-631. · 0.96 Impact Factor
  • Shafrira Greenberg, A. B. P. Lever, Clifford C. Leznoff
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    ABSTRACT: Treatment of 4-neopentoxyphthalonitrile with hydrogen sulfide gas yielded 1-imino-6-neopentoxy-3-thioisoindoline and 1-imino-5-neopentoxy-3-thioisoindoline, which on alkylation with iodomethane gave 1-imino-3-methylthio-6-neopentoxyiso-indolenine and 1-imino-3-methylthio-5-neopentoxyisoindolenine. The methylthioisoindolenines readily condensed at room temperature to a mixture of tetrasubstituted phthalocyanines and a series of linear open-chained purple compounds characteristic of isoindigos, while condensation at −20 °C in the presence of zinc acetate gave, in at least one experiment, 2,9,16,23-tetraneo-pentoxyphthalocyanine as a pure isomer. The low temperature formation of phthalocyanines is remarkable and the syntheses described herein provide guidelines for the synthesis of pure isomers of 2,9,16,23-tetrasubstituted phthalocyanines. The purple and red compounds are shown to have isoindigo structures rather than a ring-opened phthalocyanine structure as previously reported.
    Canadian Journal of Chemistry 02/2011; 66(5):1059-1064. · 0.96 Impact Factor

Publication Stats

492 Citations
150.57 Total Impact Points

Institutions

  • 1971–2011
    • York University
      • Department of Chemistry
      Toronto, Ontario, Canada
  • 2005
    • Tohoku University
      • Department of Chemistry
      Sendai-shi, Miyagi-ken, Japan
  • 1998
    • University of Windsor
      Windsor, Ontario, Canada
  • 1988
    • Soreq Nuclear Research Center
      Yerushalayim, Jerusalem District, Israel
  • 1984
    • University of Nebraska at Lincoln
      Lincoln, Nebraska, United States