Clifford C. Leznoff

York University, Toronto, Ontario, Canada

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Publications (97)84.67 Total impact

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    Dataset: LEZ105
    Hiroaki Isago, Dmitri S. Terekhov, Clifford C. Leznoff
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    Dataset: LEZ112
  • Source
    Dataset: LEZ105
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    Dataset: LEZ112
  • [show abstract] [hide abstract]
    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
  • 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
  • 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
  • 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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    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: 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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    Clifford C. Leznoff, Colin R. McArthur, Yongnian Qin
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    ABSTRACT: Five species of phthalocyanine-modified silica gels were prepared. The loadings of phthalocyanine on these silica gels were determined by acidic hydrolysis. The concept of using the aggregation phenomenon to advantage to aid chromatographic separation of unsymmetrical phthalocyanines was investigated by employing these modified silica gels as chromatographic media to purify unsymmetrical phthalocyanines. Four groups of phthalocyanine mixtures were prepared by mixed condensation. One of the desired unsymmetrical phthalocyanines was successfully purified by conventional column chromatography while others were separated by the new method described herein.
    Canadian Journal of Chemistry 02/2011; 71(9):1319-1326. · 0.96 Impact Factor
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    ABSTRACT: Semihydrogenation of 1,2-bis(3,4-dicyanophenyl)ethyne gave cis-1,2-bis(3,4-dicyanophenyl)ethene. From these precursors, binuclear phthalocyanines were produced containing linear binuclear phthalocyanines having an ethyne bridge and a mixture of cis and trans isomers of binuclear phthalocyanines linked by an ethene bridge. The cis and trans isomers could be separated and differentiated by gel permeation chromatography as the very extended trans isomer elutes faster than the cofacial globular cis isomer. Strong coupling between the conjugated binuclear phthalocyanine was not observed when examined by cyclic voltammetry. Key words: phthalocyanines, cofacial, binuclear, cyclic voltammetry.
    Canadian Journal of Chemistry 02/2011; 69(9):1457-1461. · 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
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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: 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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    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
  • 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
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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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    Clifford C. Leznoff, Shafrira Greenberg
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    ABSTRACT: Two different 2% cross-linked divinylbenzene–styrene copolymers incorporating 1,3-diol groups were prepared. The symmetrical dialdehydes terephthalaldehyde and o-phthalaldehyde were attached to these polymers through acetal formation, showing that even hindered o-aromatic dialdehydes can be monoblocked by the use of polymer supports. The free aldehyde group of polymer-bound terephthalaldehyde reacted with Wittig reagents to give 1-p-formylphenyl-4-phenyl-1,3-butadiene and p-formylstilbene. Similarly, polymer-bound o-phthalaldehyde gave o-formylstilbenes. Polymer-bound 1,3- and 1,2-diols did not form acetals of aliphatic dialdehydes and formed ketals of symmetrical diketones in very low yield.
    Canadian Journal of Chemistry 02/2011; 54(24):3824-3829. · 0.96 Impact Factor
  • Clifford C. Leznoff, Varda Yedidia
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    ABSTRACT: A 1% crosslinked divinylbenzene–styrene copolymer, incorporating benzyl alcohol groups, was used to monoblock the symmetrical diacid chlorides, ClOC(CH2)nCOCl (where n = 4 and 8). Further reaction of the polymer-bound monoester monoacid chloride with phenylmanganese iodide or butylmanganese iodide gave their respective polymer-bound tertiary hydroxyesters. Subsequent base cleavage and esterification yielded methyl 6-hydroxy-6, 6-diphenylhexanoate, methyl 10-hydroxy-10,10-diphenyldecanoate, methyl 6-butyl-6-hydroxydecanoate, and methyl 10-butyl-10-hydroxytetradecanoate and some recovered dimethyl alkanoates. The reactions of some polymer-bound monoester monoacid chlorides with phenylcadmium chloride were also studied.
    Canadian Journal of Chemistry 02/2011; 58(3):287-290. · 0.96 Impact Factor

Publication Stats

438 Citations
261 Downloads
84.67 Total Impact Points

Institutions

  • 1972–2011
    • 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