Abstract:The radical chain addition of tosyl iodide to some alkenes has been studied. The reaction was carried out at room temperature under visible light, giving the usual high yields of P-iodo sulfones. These adducts were transformed into the corresponding unsaturated sulfones. Relative reactivities of the addition of the tosyl radical to alkenes were measured in acetonitrile, dichloromethane and carbon tetrachloride, the effect of the solvent being important only with polarized alkenes, such as vinyl and allyl cyani… Show more
“…This implies some kind of interaction between monomer and catalyst. Even if more kinetic studies are needed to elucidate the mechanism of this initiation, the ratio between various k i app reported here (with the exeption of BA) are in excelent agreement with data available in the literature, even if the literature data were generated in the absence of CuCl (Table ). 7 Determination of the external order of reaction of the rate of initiation of MA (a) and MMA (b) initiated with MBSC in p -xylene at 36 °C ([MBSC] = 0.3 M, [MBSC]/[CuCl]/[bpy9] = 1:0.3:0.42 molar ratios), and (c) determination of the external order of reaction of the rate of initiation of MMA with MBSC in CuCl concentration ([MMA] = 3.12 M, [MMA]/[MBSC] = 10:1 and [CuCl]/[bpy9] = 1:1.3 molar ratios, 32 °C).…”
The complex Cu(I)Cl/4,4‘-dinonyl-2,2‘-bipyridine (bpy9)
catalyzes via a redox process the
homogeneous “living” radical polymerization of styrene(s),
methacrylates, and acrylates initiated with a variety
of functional phenylsulfonyl chlorides. Polymers with narrow
molecular weight distribution and molecular
weights close to the theoretical ones are obtained from these three
classes of monomers. Kinetics of propagation
and initiation were performed with selected substituted phenylsulfonyl
chlorides and with their monoadducts
to monomer. Polymerizations follow first-order kinetics internally
in monomer and externally in Cu(I)Cl
while initiation is first order internally in initiator and in
Cu(I)Cl concentrations. A catalyst
concentration
dependence of the optimum bpy9/Cu(I)Cl ratio which yields the
largest rate constant of polymerization was
observed. The apparent rate constants of propagation corrected for
catalyst concentration are in the order:
methacrylates > styrene > acrylates. This inversion from the
classic dependence of the corresponding absolute
rate constants (acrylates > methacrylates > styrene) was shown to be
determined by a different steady-state
concentration of propagating radicals which is in dynamic equilibrium
with an extremely large excess of the
corresponding dormant C−Cl species. The formation and the
concentration of the radical species is determined
by the C−Cl bond strength of the dormant species. Apparent rate
constants of initiation corrected for catalyst
concentration are in the order: styrene > methacrylates >
acrylates. Within experimental error, initiation
efficiency is 100% and the apparent rate constants of initiation are 4
(for styrene and methacrylates) and 3 or
2 (for acrylates) orders of magnitude higher than those of propagation.
The absence of conjugation between
the sulfonyl radical and its phenyl group generates a small effect of
the phenyl group substituent on the rate
constant of initiation. These results demonstrate that
arenesulfonyl chlorides are the first class of
universal
functional
initiators for the metal-catalyzed
“living” radical polymerization of styrene(s), methacrylates,
and
acrylates. This discovery provides numerous fundamental and
technological opportunities in the field of
controlled radical polymerization and copolymerization, of well-defined
functional polymers and copolymers
with complex architecture, and of self-organized supramolecular systems
based on them.
“…This implies some kind of interaction between monomer and catalyst. Even if more kinetic studies are needed to elucidate the mechanism of this initiation, the ratio between various k i app reported here (with the exeption of BA) are in excelent agreement with data available in the literature, even if the literature data were generated in the absence of CuCl (Table ). 7 Determination of the external order of reaction of the rate of initiation of MA (a) and MMA (b) initiated with MBSC in p -xylene at 36 °C ([MBSC] = 0.3 M, [MBSC]/[CuCl]/[bpy9] = 1:0.3:0.42 molar ratios), and (c) determination of the external order of reaction of the rate of initiation of MMA with MBSC in CuCl concentration ([MMA] = 3.12 M, [MMA]/[MBSC] = 10:1 and [CuCl]/[bpy9] = 1:1.3 molar ratios, 32 °C).…”
The complex Cu(I)Cl/4,4‘-dinonyl-2,2‘-bipyridine (bpy9)
catalyzes via a redox process the
homogeneous “living” radical polymerization of styrene(s),
methacrylates, and acrylates initiated with a variety
of functional phenylsulfonyl chlorides. Polymers with narrow
molecular weight distribution and molecular
weights close to the theoretical ones are obtained from these three
classes of monomers. Kinetics of propagation
and initiation were performed with selected substituted phenylsulfonyl
chlorides and with their monoadducts
to monomer. Polymerizations follow first-order kinetics internally
in monomer and externally in Cu(I)Cl
while initiation is first order internally in initiator and in
Cu(I)Cl concentrations. A catalyst
concentration
dependence of the optimum bpy9/Cu(I)Cl ratio which yields the
largest rate constant of polymerization was
observed. The apparent rate constants of propagation corrected for
catalyst concentration are in the order:
methacrylates > styrene > acrylates. This inversion from the
classic dependence of the corresponding absolute
rate constants (acrylates > methacrylates > styrene) was shown to be
determined by a different steady-state
concentration of propagating radicals which is in dynamic equilibrium
with an extremely large excess of the
corresponding dormant C−Cl species. The formation and the
concentration of the radical species is determined
by the C−Cl bond strength of the dormant species. Apparent rate
constants of initiation corrected for catalyst
concentration are in the order: styrene > methacrylates >
acrylates. Within experimental error, initiation
efficiency is 100% and the apparent rate constants of initiation are 4
(for styrene and methacrylates) and 3 or
2 (for acrylates) orders of magnitude higher than those of propagation.
The absence of conjugation between
the sulfonyl radical and its phenyl group generates a small effect of
the phenyl group substituent on the rate
constant of initiation. These results demonstrate that
arenesulfonyl chlorides are the first class of
universal
functional
initiators for the metal-catalyzed
“living” radical polymerization of styrene(s), methacrylates,
and
acrylates. This discovery provides numerous fundamental and
technological opportunities in the field of
controlled radical polymerization and copolymerization, of well-defined
functional polymers and copolymers
with complex architecture, and of self-organized supramolecular systems
based on them.
“…In the above calculations the polar and enthalpy effects were found to be the dominant factors influencing radical addition reactions. In addition to polar and enthalpy effects, however, steric and solvent effects may also influence these reactions. ,,, The α-steric effects were minimized by choosing vinyl-type alkenes for the investigations. Our analysis revealed no β-steric and solvent effects.…”
Section: Discussionmentioning
confidence: 99%
“…The rate constants and barrier height values used in the calculations were collected from the literature, 1a,,,,,,,,,, and they are given as Supporting Information. In addition to the radical reactivities, three descriptors were also considered as follows: electron affinity (EA) and negative ionization potential (−IP) of alkenes, as well as exothermicity (−Δ H r , negative enthalpy) of reactions between the alkenes and the methyl radical chosen as a model.…”
Section: Methodsmentioning
confidence: 99%
“…The most widespread method in the literature to classify radicals according to nucleophilicity and electrophilicity is a simple regression analysis of radical reactivity data as a function of certain descriptors (Hammett σ p substituent constant, electron affinity, and ionization potential). − ,,,,− …”
Section: Introductionmentioning
confidence: 99%
“…However, electrophilic radicals such as dicyanomethyl, phenylsulfonyl, tert -butoxyl, phenylthiyl, p -chlorophenylthiyl, diethyl α-benzylmalonyl, nitrate, perfluoroalkyls, tosyl, methylmalononitrile, perhaloalkylperoxyl, azidyl, and 2,2-dimethyl-4,6-dioxo-1,3-dioxan-5-yl 33 can also be found in the literature. Unfortunately, a sufficient number of rate constants are available only for the reactions of phenylsulfonyl, tosyl, and 2,2-dimethyl-4,6-dioxo-1,3-dioxan-5-yl radicals with the alkenes involved in our previous calculations 1a…”
Principal component analysis (PCA) was performed on experimental rate constant and theoretical
barrier height data of radical addition reactions involving various carbon- and sulfur-centered
radicals and vinyl-type alkenes. Altogether six data sets were analyzed. In three cases the reactivity
data were completed by certain descriptors, i.e., the electron affinity (EA) and negative ionization
potential (−IP) of alkenes, as well as the exothermicity (−ΔH
r) of reactions. It was found that in
each case the first two principal components account for more than 93% of the total variance in
the data. The scores of the first principal component correlate with EA and (−ΔH
r), whereas those
of the second principal component with (−IP). It is concluded that PCA is able to decompose both
experimental and theoretical reactivity data into nucleophilic and electrophilic components, as well
as into polar and enthalpy terms. In the plots of component loadings the radicals form significant
groups depending on their character. Thus, PCA can classify radicals according to nucleophilicity
and electrophilicity. The PCA results were validated by significant correlations of experimental
and theoretical reactivity data with Hammett σp as well as with the descriptors EA, (−ΔH
r), and
(−IP). The hydroxymethyl radical is classified as strongly nucleophilic, the methyl radical as
moderately nucleophilic, the tert-butoxycarbonylmethyl and cyanomethyl radicals as weakly
nucleophilic, the phenylsulfonyl and tosyl radicals as moderately electrophilic, and the 2,2-dimethyl-4,6-dioxo-1,3-dioxan-5-yl radical as strongly electrophilic. It is concluded that the reactivities of
tert-butoxycarbonylmethyl and cyanomethyl radicals are mainly governed by enthalpy effects. This
conclusion is in agreement with the findings of Giese et al. [Chem.
Ber.
1988, 121, 2063−2066]
and Fischer et al. [Helv.
Chim. Acta
1995, 78, 194−214]. A symmetry pattern of correlations is
proposed: the reactivity correlates with EA for strongly nucleophilic radicals, with EA and (−ΔH
r)
for moderately nucleophilic radicals, with (−ΔH
r) for weakly nucleophilic or weakly electrophilic
radicals, with (−ΔH
r) and (−IP) for moderately electrophilic radicals, and with (−IP) for strongly
electrophilic radicals. On the basis of the symmetry pattern of correlations, it is concluded that
the dominant factors influencing radical addition reactions are polar effects alone for strongly
nucleophilic or strongly electrophilic radicals, polar and enthalpy effects for moderately nucleophilic
or moderately electrophilic radicals, and enthalpy effects alone for weakly nucleophilic or weakly
electrophilic radicals.
A simple, practical, and metal‐free protocol has been developed for the synthesis of sulfonamides from sodium sulfinates and various amines through an iodine‐mediated SN bond formation reaction at room temperature. This green reaction is cost‐effective, operationally straightforward, and especially proceeds under very mild conditions to afford the target products in good to excellent yields (up to 98%).magnified image
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