Showing papers by "Samir Z. Zard published in 2000"
TL;DR: The key parameter for the control with N,N-disubstituted (A) or cyclic (B) dithiocarbamates was found to be the conjugation of the lone pair of electrons of the nitrogen atom with carbonyl or aromatic groups.
Abstract: Control of the radical polymerization of acrylates, styrene and vinyl acetate has been achieved by using novel dithiocarbamates as reversible addition-fragmentation chain transfer agents. The key parameter for the control with N,N-disubstituted (A) or cyclic (B) dithiocarbamates was found to be the conjugation of the lone pair of electrons of the nitrogen atom with carbonyl or aromatic groups.
301 citations
TL;DR: An unusual radical-mediated fusion of a seven-membered ring onto an aromatic system exploits the relatively long lifetime of radicals generated using dithiocarbonares (xanthates) as discussed by the authors.
Abstract: An unusual radical-mediated fusion of a seven-membered ring onto an aromatic system exploits the relatively long lifetime of radicals generated using dithiocarbonares (xanthates). This type of annelation (an example is shown), which was hitherto very difficult to accomplish by more traditional radical methods, was used to construct a variety of complex structures. Y = OAc, CN, (CH2)8OAc, CH2CO2Et, phthaloyl.
82 citations
TL;DR: Intermolecular radical additions to various strained olefins such as cyclopropenes, cyclobutenes, azetines and methylenecyclopropanes can be accomplished using the xanthate transfer method; the adducts may undergo further cyclisation to give polycyclic structures as discussed by the authors.
40 citations
TL;DR: Intermolecular radical addition of a xanthyl phosphonoacetate to a γ,δ-enone gives rise to an adduct suitable for a base 龍円-induced Horner-Emmons ring closure to a cyclohexene derivative, after the reductive removal of the xanthate group as mentioned in this paper.
20 citations
TL;DR: In this paper, various complex structures can be attached to a polystyrene oligomer using the simple but powerful xanthate transfer technology; the material obtained is soluble in many of the common organic solvents allowing further reactions under homogeneous conditions, but can be precipitated with methanol making this technique especially suitable for conducting parallel syntheses.
16 citations
2 citations
Patent•
28 Oct 2000
TL;DR: In this paper, the authors describe a process for polymerizing block polymers of general formula (I): in which process the following are brought into contact with each other: an ethylenically unsaturated monomer of formula: CYY'(=CW-CW')a=CH2, a precursor compoun of generic formula (II): a radical polymerization initiator.
Abstract: PCT No. PCT/FR98/01316 Sec. 371 Date Jan. 14, 1999 Sec. 102(e) Date Jan. 14, 1999 PCT Filed Jun. 23, 1998 PCT Pub. No. WO98/58974 PCT Pub. Date Dec. 30, 1998The invention relates to a process for polymerizing block polymers of general formula (I): in which process the following are brought into contact with each other: an ethylenically unsaturated monomer of formula: CYY'(=CW-CW')a=CH2, a precursor compoun of general formula (II): a radical polymerization initiator.
1 citations
TL;DR: In this paper, the 9-membered rings are constructed through a radical addition-cyclisation sequence on a 1,6-dien-3-ol system followed by a Grob-type fragmentation.
Abstract: 9-Membered rings are readily constructed through a radical addition-cyclisation sequence on a 1,6-dien-3-ol system followed by a Grob-type fragmentation.
TL;DR: In this paper, S-Propargyl xanthates exihibit a special behavior which involves a sigmatropic rearrangement to the corresponding allene and ring closure to a novel betaine.
Abstract: Xanthates are convenient precursors of a variety of radicals that can be captured in an inter-or intramolecular fashion. Overall, the process involves rupture of the sulfide C-S bond and addition of the elements of the xanthate to the olefinic trap. The xanthate in the product can be used in another radical sequence or ionically modified in a grear variety of ways. S-Propargyl xanthates exihibit a special but interesting behaviour which involves a sigmatropic rearrangement to the corresponding allene and ring closure to a novel betaine.
TL;DR: An unusual radical-mediated fusion of a seven-membered ring onto an aromatic system exploits the relatively long lifetime of radicals generated using dithiocarbonares (xanthates) as mentioned in this paper.
Abstract: An unusual radical-mediated fusion of a seven-membered ring onto an aromatic system exploits the relatively long lifetime of radicals generated using dithiocarbonares (xanthates). This type of annelation (an example is shown), which was hitherto very difficult to accomplish by more traditional radical methods, was used to construct a variety of complex structures. Y = OAc, CN, (CH2)8OAc, CH2CO2Et, phthaloyl.