The Experts below are selected from a list of 93 Experts worldwide ranked by ideXlab platform

Sanjib Kar - One of the best experts on this subject based on the ideXlab platform.

  • reactions of grignard reagents with tin corrole complexes demetalation strategy and σ methyl phenyl complexes
    2014
    Co-Authors: Woormileela Sinha, Sanjib Kar
    Abstract:

    An efficient, mild, and one-step methodology for the conversion of tin-corroles to the corresponding free base corroles has been developed. The Grignard reagent, namely, Methylmagnesium Chloride, is responsible for the facile demetalation of tin-corroles. In an optimized reaction, almost complete destannation is observed using Methylmagnesium Chloride in a representative corrolato-Sn(IV)-Chloride complex. This particular protocol has also been proven to be versatile on a wide variety of corrolato-Sn(IV)-Chloride substrates. Similar Grignard reagents, namely, methyl/phenylmagnesium bromides, however, failed to perform the desired demetalation reaction and rather resulted in the usual σ-methyl/phenyl complexes in good yields. In addition to two novel σ-phenyl complexes and three novel σ-methyl complexes, one new A3-corrole and one new corrolato Sn(IV)Chloride have also been synthesized. All the complexes have been thoroughly characterized by various spectroscopic techniques, including single-crystal X-ray s...

  • Reactions of Grignard Reagents with Tin-Corrole Complexes: Demetalation Strategy and σ‑Methyl/Phenyl Complexes
    2014
    Co-Authors: Woormileela Sinha, Sanjib Kar
    Abstract:

    An efficient, mild, and one-step methodology for the conversion of tin-corroles to the corresponding free base corroles has been developed. The Grignard reagent, namely, Methylmagnesium Chloride, is responsible for the facile demetalation of tin-corroles. In an optimized reaction, almost complete destannation is observed using Methylmagnesium Chloride in a representative corrolato-Sn­(IV)-Chloride complex. This particular protocol has also been proven to be versatile on a wide variety of corrolato-Sn­(IV)-Chloride substrates. Similar Grignard reagents, namely, methyl/phenylmagnesium bromides, however, failed to perform the desired demetalation reaction and rather resulted in the usual σ-methyl/phenyl complexes in good yields. In addition to two novel σ-phenyl complexes and three novel σ-methyl complexes, one new A3-corrole and one new corrolato Sn­(IV)­Chloride have also been synthesized. All the complexes have been thoroughly characterized by various spectroscopic techniques, including single-crystal X-ray structural analysis of the representative complexes. In the single-crystal X-ray data analyses, it was observed that the Sn–N and Sn–C bond distances are shorter than those in the similar tin porphyrin analogues. The 1H NMR spectrum of a representative σ-methyl complex exhibits peaks corresponding to σ-bonded methyl groups in the high field regions at −3.39 ppm

Woormileela Sinha - One of the best experts on this subject based on the ideXlab platform.

  • reactions of grignard reagents with tin corrole complexes demetalation strategy and σ methyl phenyl complexes
    2014
    Co-Authors: Woormileela Sinha, Sanjib Kar
    Abstract:

    An efficient, mild, and one-step methodology for the conversion of tin-corroles to the corresponding free base corroles has been developed. The Grignard reagent, namely, Methylmagnesium Chloride, is responsible for the facile demetalation of tin-corroles. In an optimized reaction, almost complete destannation is observed using Methylmagnesium Chloride in a representative corrolato-Sn(IV)-Chloride complex. This particular protocol has also been proven to be versatile on a wide variety of corrolato-Sn(IV)-Chloride substrates. Similar Grignard reagents, namely, methyl/phenylmagnesium bromides, however, failed to perform the desired demetalation reaction and rather resulted in the usual σ-methyl/phenyl complexes in good yields. In addition to two novel σ-phenyl complexes and three novel σ-methyl complexes, one new A3-corrole and one new corrolato Sn(IV)Chloride have also been synthesized. All the complexes have been thoroughly characterized by various spectroscopic techniques, including single-crystal X-ray s...

  • Reactions of Grignard Reagents with Tin-Corrole Complexes: Demetalation Strategy and σ‑Methyl/Phenyl Complexes
    2014
    Co-Authors: Woormileela Sinha, Sanjib Kar
    Abstract:

    An efficient, mild, and one-step methodology for the conversion of tin-corroles to the corresponding free base corroles has been developed. The Grignard reagent, namely, Methylmagnesium Chloride, is responsible for the facile demetalation of tin-corroles. In an optimized reaction, almost complete destannation is observed using Methylmagnesium Chloride in a representative corrolato-Sn­(IV)-Chloride complex. This particular protocol has also been proven to be versatile on a wide variety of corrolato-Sn­(IV)-Chloride substrates. Similar Grignard reagents, namely, methyl/phenylmagnesium bromides, however, failed to perform the desired demetalation reaction and rather resulted in the usual σ-methyl/phenyl complexes in good yields. In addition to two novel σ-phenyl complexes and three novel σ-methyl complexes, one new A3-corrole and one new corrolato Sn­(IV)­Chloride have also been synthesized. All the complexes have been thoroughly characterized by various spectroscopic techniques, including single-crystal X-ray structural analysis of the representative complexes. In the single-crystal X-ray data analyses, it was observed that the Sn–N and Sn–C bond distances are shorter than those in the similar tin porphyrin analogues. The 1H NMR spectrum of a representative σ-methyl complex exhibits peaks corresponding to σ-bonded methyl groups in the high field regions at −3.39 ppm

Michal Hocek - One of the best experts on this subject based on the ideXlab platform.

  • regioselectivity in cross coupling reactions of 2 6 8 trichloro 9 tetrahydropyran 2 yl purine synthesis of 2 6 8 trisubstituted purine bases
    2004
    Co-Authors: Michal Hocek, Radek Pohl
    Abstract:

    The regioselectivity of cross-coupling reactions (Pd-catalyzed Suzuki-Miyaura reactions with phenylboronic acid and Fe-catalyzed reactions with Methylmagnesium Chloride) of 2,6,8-trichloro-9-(tetrahydropyran-2-yl)purine with varying amounts of the organometallic reagent was studied. In general, the regioselectivity of these reactions was quite low giving mixtures of isomers of mono-, di- and trisubstituted products. Nevertheless, 2,6-dichloro8-methyl-9-THP-purine (laab), 2-chloro-6,8-dimethyl-9-THP-purine (labb) and 2,8-dichloro-6-phenyl-9-THP-purine (laca) were isolated in acceptable yields and used as intermediates for further cross-coupling reactions giving a series of 2,6,8-trisubstituted 9-THP-purines that were deprotected to the corresponding purine bases. Characteristic 1 3 C NMR shifts cf CH 3 or ipso-Ph carbons in different positions of the purine ring have been observed enabling rapid and facile identification of the particular isomer.

  • dichotomy in regioselective cross coupling reactions of 6 8 dichloropurines with phenylboronic acid and Methylmagnesium Chloride synthesis of 6 8 disubstituted purines
    2004
    Co-Authors: Michal Hocek, Dana Hockova, Hana Dvořakova
    Abstract:

    Pd-catalyzed cross-coupling reaction of 6,8-dichloro-9-(tetrahydropyran-2-yl)purine with one equivalent of phenylboronic acid proceeded regioselectively to give 8-chloro-6-phenylpurine, while the analogous Fe-catalyzed reaction with Methylmagnesium Chloride gave the 6-chloro-8-methylpurine derivative as major product. Both types of the monochloropurine intermediates were subjected to other cross-coupling reactions or nucleophilic substitutions affording the 9-(tetrahydropyran-2-yl)-6,8-disubstituted purines that were easily deprotected to 8-substituted 6-phenylpurines or 6-substituted 8-methylpurines. Attempted analogous reactions with benzylmagnesium Chloride and phenylmagnesium bromide gave low conversions and little selectivity.

Radek Pohl - One of the best experts on this subject based on the ideXlab platform.

  • regioselectivity in cross coupling reactions of 2 6 8 trichloro 9 tetrahydropyran 2 yl purine synthesis of 2 6 8 trisubstituted purine bases
    2004
    Co-Authors: Michal Hocek, Radek Pohl
    Abstract:

    The regioselectivity of cross-coupling reactions (Pd-catalyzed Suzuki-Miyaura reactions with phenylboronic acid and Fe-catalyzed reactions with Methylmagnesium Chloride) of 2,6,8-trichloro-9-(tetrahydropyran-2-yl)purine with varying amounts of the organometallic reagent was studied. In general, the regioselectivity of these reactions was quite low giving mixtures of isomers of mono-, di- and trisubstituted products. Nevertheless, 2,6-dichloro8-methyl-9-THP-purine (laab), 2-chloro-6,8-dimethyl-9-THP-purine (labb) and 2,8-dichloro-6-phenyl-9-THP-purine (laca) were isolated in acceptable yields and used as intermediates for further cross-coupling reactions giving a series of 2,6,8-trisubstituted 9-THP-purines that were deprotected to the corresponding purine bases. Characteristic 1 3 C NMR shifts cf CH 3 or ipso-Ph carbons in different positions of the purine ring have been observed enabling rapid and facile identification of the particular isomer.

Chuchuryukin A.v. - One of the best experts on this subject based on the ideXlab platform.

  • NCN-Pincer Metal Complexes (Ti, Cr, V, Zr, Hf, and Nb) of the Phebox Ligand (S,S)-2,6-Bis(4′-isopropyl-2′-oxazolinyl)phenyl
    2011
    Co-Authors: Chuchuryukin A.v., Huang R., Lutz M., Chadwick J.c., Spek A.l., Van Koten G.
    Abstract:

    Reaction of (S,S)-2,6-bis(4′-isopropyl-2′-oxazolinyl)phenyllithium (i-Pr-Phebox-Li) (2a) with 4,4′-bis[P-(chlorogold(I))diphenylphosphino]biphenyl [(dppbp)(AuCl)2] (5) afforded the new, bimetallic gold complex 4,4′-bis[P-(η1-C-i-Pr-Phebox-gold)diphenylphosphino]biphenyl [(P-Au(η1-C-i-Pr-Phebox))2(dppbp)] (6). Transmetalation of 6 with 2 equiv of Cl3MX (MX = TiOi-Pr, VCl, CrPy, ZrCl, HfCl, NbO) afforded the corresponding monopincer compounds [MCl2X(i-Pr-Phebox)] (M = Ti, V, Cr) (7) and [MCl2X(i-Pr-Phebox)]2 (M = Zr, Hf, Nb) (8) in high yields and the gold starting material 5, which could be quantitatively recovered and reused. The structures in the solid state of the digold compound 6, the monopincer compounds R-PheboxAu(PPh3) (R = i-Pr, t-Bu), and a number of Phebox-ETM complexes (7a, 7b, 7c, 8a, 8b, and 8c) were obtained. In each of these structures the i-Pr-Phebox monoanion is mer-N,C,N-tridentate bonded. The monopincer Phebox-Zr and -Hf compounds are dimeric because of two bridging Chlorides, while the corresponding Nb compound has bridging oxygen atoms. Reaction of 6 with iron(III) Chloride resulted in the formation of a N4(FeCl2)2 complex, characterized by X-ray crystal structure determination, comprising a bridging, tetradentate N4 ligand formed by C–C coupling of two Phebox anions to a biphenyl species. The new Phebox complexes 7 and 8 have been tested as olefin polymerization precatalysts. Rapid catalyst deactivation was observed in ethene polymerization under homogeneous conditions, whereas stable activity was obtained after immobilization on MgCl2-based supports. From preliminary investigations on the reaction of 8a with either Methylmagnesium Chloride or methyllithium we assume that the low reactivity in homogeneous polymerization is due to the alkylation of the Phebox ligand

  • NCN-pincer metal complexes (Ti, Cr, V, Zr, Hf, and Nb) of the phebox ligand (S,S)-2,6-Bis(4'-isopropyl-2'-oxazolinyl)phenyl
    2011
    Co-Authors: Chuchuryukin A.v., Huang R., Lutz M., Chadwick J.c., Spek A.l., Koten, Van G.
    Abstract:

    Reaction of (S,S)-2,6-bis(4'-isopropyl-2'-oxazolinyl)phenyllithium (i-Pr-Phebox-Li) (2a) with 4,4'-bis[P-(chlorogold(I))diphenylphosphino]biphenyl [(dppbp)(AuCl)2] (5) afforded the new, bimetallic gold complex 4,4'-bis[P-(¿1-C-i-Pr-Phebox-gold)diphenylphosphino]biphenyl [(P-Au(¿1-C-i-Pr-Phebox))2(dppbp)] (6). Transmetalation of 6 with 2 equiv of Cl3MX (MX = TiOi-Pr, VCl, CrPy, ZrCl, HfCl, NbO) afforded the corresponding monopincer compounds [MCl2X(i-Pr-Phebox)] (M = Ti, V, Cr) (7) and [MCl2X(i-Pr-Phebox)]2 (M = Zr, Hf, Nb) (8) in high yields and the gold starting material 5, which could be quantitatively recovered and reused. The structures in the solid state of the digold compound 6, the monopincer compounds R-PheboxAu(PPh3) (R = i-Pr, t-Bu), and a number of Phebox-ETM complexes (7a, 7b, 7c, 8a, 8b, and 8c) were obtained. In each of these structures the i-Pr-Phebox monoanion is mer-N,C,N-tridentate bonded. The monopincer Phebox-Zr and -Hf compounds are dimeric because of two bridging Chlorides, while the corresponding Nb compound has bridging oxygen atoms. Reaction of 6 with iron(III) Chloride resulted in the formation of a N4(FeCl2)2 complex, characterized by X-ray crystal structure determination, comprising a bridging, tetradentate N4 ligand formed by C–C coupling of two Phebox anions to a biphenyl species. The new Phebox complexes 7 and 8 have been tested as olefin polymerization precatalysts. Rapid catalyst deactivation was observed in ethene polymerization under homogeneous conditions, whereas stable activity was obtained after immobilization on MgCl2-based supports. From preliminary investigations on the reaction of 8a with either Methylmagnesium Chloride or methyllithium we assume that the low reactivity in homogeneous polymerization is due to the alkylation of the Phebox ligand