Cation radical chain cycloaddition polymerization: A fundamentally new polymerization mechanism

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY

J. Phys. Org. Chem. 12, 808–818 (1999)

Cation radical chain cycloaddition polymerization:

a fundamentally new polymerization mechanism

Nathan L. Bauld,* Daxin Gao and J. Todd Aplin

Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, USA

Received 26 April 1999; revised 4 August 1999; accepted 4 August 1999

ABSTRACT: Cation radical chain cycloaddition polymerization, a fundamentally new addition polymerization

method involving cation radical intermediates in each propagation step, is described and demonstrated. The

cycloaddition reactions of appropriately constituted difunctional monomers, catalyzed by tris(4-bromophenyl)ami-

nium hexachloroantimonate in dichloromethane solvent at 0°C, is shown to afford polymers having average

molecular weights of up to 150000. Both cyclobutanation and Diels–Alder polymers were obtained in this way. The

surprising efﬁciency of these polymerization reactions is believed to be the result of rapid intramolecular hole transfer

from the site at which the hole is originally generated in the cycloaddition step to a reactive, terminal alkene moiety.

Consequently, chain propagation is much more efﬁcient than in the cycloadditions of corresponding monofunctional

KEYWORDS: cation radical chain cycloaddition polymerization; intramolecular hole transfer; chain propagation

INTRODUCTION

in the cycloaddition reaction (which in the example

illustrated in Scheme 2 is the cyclobutane ring) to a

reactive terminal alkene site. The operation of a catalytic

mechanism in the context of the cation radical poly-

merization of a bifunctional molecule then necessarily

Cation radical cycloaddition reactions potentially can

occur via either a catalytic or chain mechanism (Scheme

1

1). In the speciﬁc context of an aminium salt-induced

cycloaddition, the substrate molecule (S) is ionized to the

corresponding cation radical by intermolecular hole

transfer from the aminium salt. The substrate cation

radical then cycloadds to a molecule of neutral substrate

to yield a cyclodimer cation radical, which then must be

neutralized by hole transfer to an appropriate neutral

molecule. If the single electron donor is the neutral

triarylamine, which is formed in the ﬁrst step and also by

decomposition of the aminium salt,²the aminium salt

catalyst is regenerated, resulting in a true catalytic

mechanism. If, on the other hand, the hole transfer is to

neutral S as the single electron donor, the cation radical

of the substrate is generated and the resulting mechanism

is a cation radical chain mechanism.

In the context of cation radical cycloadditions of

difunctional molecules (Scheme 2), addition polymeriza-

tion is at least a formal possibility. A key requirement for

polymerization is the transfer of the hole, either directly

or indirectly, from the site at which it is initially formed

*Correspondence to: N. L. Bauld, Department of Chemistry and

Biochemistry, University of Texas at Austin, Austin, Texas 78712,

USA.

Contract/grant sponsor: National Science Foundation; Contract/grant

number: CHE-9610227.

Contract/grant sponsor: Robert A. Welch Foundation; Contract/grant

number: F-149.

Scheme 1. Chain vs catalytic mechanisms of cation radical

cycloadditions

CCC 0894–3230/99/110808–11 $17.50

CATIONIC RADICAL CHAIN CYCLOADDITION POLYMERIZATION

809

Scheme 4. Cation radical cyclobutadimerization of trans-

anethole

given appropriate linkers and a sufﬁciently exergonic

hole transfer, intramolecular hole transfer can be

exceptionally rapid, it appears not unreasonable to

postulate an intrinsic advantage for cation radical chain

polymerization over cation radical cycloadditions of

corresponding neutral monofunctional molecules, based

upon the advantage of intramolecular hole transfer over

intermolecular hole transfer. Consequently, the possibi-

lity of relatively efﬁcient cation radical chain polymer-

ization was considered a realistic one in spite of the

modest efﬁciency of most aminium salt-induced cation

radical cycloadditions.

Scheme 2. Cation radical cyclobutanation polymerization

involves a step growth polymerization process (Scheme

3). This follows because, in this mechanism, the dimer

cation radical is always neutralized by the triarylamine to

the corresponding neutral dimer, and therefore further

oligomerization and polymerization must involve the

successive re-ionization of the dimer and each higher

oligomer, in turn, by the aminium salt. Given the yields in

typical cycloaddition reactions of monofunctional sub-

strates (ca 30–80%),³and the stringent requirements

upon the yields in the individual (consecutive) reactions

of an efﬁcient step growth polymerization,⁴the prospects

for efﬁcient catalytic cation radical cycloaddition poly-

merization would not appear to be encouraging. Even in

the case of a cation radical chain mechanism, one of the

two possible scenarios also leads to a relatively

undesirable step growth mechanism (Scheme 3). Thus,

RESULTS AND DISCUSSION

Cyclobutanation was selected as the speciﬁc cycloaddi-

tion type for initial, exploratory studies, especially since

this cycloaddition mode requires only a single, symme-

trical difunctional monomer. Further, since the cyclobu-

tadimerization of trans-anethole has been studied fairly

extensively,^2,5,6this reaction was chosen as a monofunc-

tional model for these studies (Scheme 4). Monomer 2

(Scheme 5) was therefore selected as an appropriately

close difunctional analogue of trans-anethole. In fact, 2

has an oxidation potential which is essentially identical

with that of trans-anethole (both have peak potentials at

1.23V vs SCE⁷). The synthesis of 2 from commercially

Á

if the dimer cation radical D is neutralized by hole

transfer to the monomer prior to intramolecular hole

transfer, a step growth process once again results.

Á

However, if intramolecular hole transfer to give D' is

faster than intermolecular hole transfer to the monomer, a

chain polymerization process can be the result. Since,

Scheme 3. Chain growth vs step growth polymerization

J. Phys. Org. Chem. 12, 808–818 (1999)

810

N. L. BAULD, D. GAO AND T. APLIN

Scheme 5. A cation radical chain cyclobutanation polymerization

available 1,2-diphenoxyethane via propionylation, re-

duction and dehydration is straightforward. The poly-

merization of 2 in saturated dichloromethane solution

(0.056 M) at ambient temperature (the low solubility of

2 at 0°C was problematic) in the presence of 15 mol%

of tris(4-bromophenyl)aminium hexachloroantimonate

merization of 2 has already appeared⁸). After a reaction

time of 7 min, the monomer had been completely

consumed and the resulting polymer had M_w= 9400

[polydispersity index (PDI) = 5.30]. The crude polymer

was subsequently puriﬁed by chromatography on alumi-

na, but the NMR spectra of the crude and puriﬁed

polymers were essentially identical except for the

presence of the spent catalyst (the neutral triarylamine)

Á

(1 ) proceeded fairly smoothly to the desired cyclobu-

tapolymer (a preliminary report on the cyclobutapoly-

Scheme 6. Mechanism of cation radical cycloaddition polymerization of 2

J. Phys. Org. Chem. 12, 808–818 (1999)

CATIONIC RADICAL CHAIN CYCLOADDITION POLYMERIZATION

811

Scheme 7. Synthesis of a more soluble monomer

1

in the crude polymer. The H NMR spectrum of the

polymer (55°C, CDCl₃) shows broadened absorptions at

ꢀ 1.1 (diagnostic for methyl attached to a cyclobutane

ring), 1.7 (the non-benzylic methine), 2.7 (the benzylic

methine), 4.1 (the ether methylenes) and 6.8,7.0 (aro-

matic protons), corresponding closely to the absorptions

of the trans,anti,trans-cyclobutadimer of trans-anethole.

In addition, weak propenyl end-group absorptions are

found at ꢀ 1.8, 6.0 and 6.3. The ¹³C NMR spectrum under

the same conditions has absorptions at ꢀ 18.8, 43.3, 52.5,

66.8, 114.6, 127.7, 136.2 and 157.0, again corresponding

very closely to those of the trans,anti,trans-cyclobutadi-

mer of trans-anethole. When the reaction of 2 is carried

out for a longer time (10 min), the polymer has

initially formed diarylcyclobutane cation radical to the

trans-anethole-like terminal site occurs via bonds or

through space is not yet clear, but efﬁcient transmission

via the ethylenedioxy linkage is by no means implausible.

That the cation radical cyclobutapolymerization of 2 is a

chain growth process is strongly suggested by the

theoretical arguments developed in the introduction,

and is further supported by experimental observations.

First, the observed polydispersity indices are much higher

than the theoretical maximum of 2.0 for a step growth

process.¹⁰Further, studies of the molecular weights of the

polymers generated at early reaction times, i.e. under

conditions where the monomer is only partially con-

sumed, yield molecular weights which are very much

larger than those predicted for a step growth process.

Speciﬁcally, the M_win a step growth process is

proportional to the monomer molecular weight and to

the quantity (1 p)/(1 p), where p is the fraction of the

monomer which has been consumed.¹⁰In the case where

p = 0.82, the molecular weight of the polymer generated

from 2 (which has a molecular weight of 294)) via a step

growth process should be 2973, whereas that actually

observed was 15300. Similarly, the predicted molecular

weight in the case where p = 0.5 is only 882 (average

trimer), whereas an average molecular weight of 5000

was observed experimentally. It is important to note that

the efﬁciency of these polymerizations varies from batch

to batch of the initiator and with monomer purity. In

comparison experiments, it is therefore essential to run

side-by-side experiments.

M_w= 37000 (PDI = 7.31), and the H and ¹³C NMR

1

spectra are closely comparable to those of the lower

molecular weight polymer and the trans-anethole cyclo-

butadimer. In addition to the absorption in the ¹H NMR at

ꢀ 1.1, corresponding to the methyl groups attached to a

cyclobutane ring, a much weaker absorption at 0.7–0.9

was also observed, corresponding to methyl groups

attached to either acyclic carbons or to a cyclohexane

ring. This absorption amounted to no more than 10–15%

of the ꢀ 1.1 absorption and was observed, at least to some

extent, even when the polymerizations were run in the

presence of sodium carbonate or di-tert-butylpyridine.

Conceivably this could correspond in part to the

competing production of some acyclic polymer resulting

from acid-catalyzed, carbocation-mediated polymeriza-

tion or from cationic block polymerization of the termini

of the cation radical polymer. However, the fact that the

absorptions were found even under basic conditions

suggests that, at least in part, these absorptions could be

the result of extraneous substances introduced during

workup and handling.

A limiting factor in the case of the cyclobutapolymer-

ization of 2 is its relatively low solubility in dichloro-

methane at 0°C (ca 0.05 M). In order to increase the

degree of polymerization, an appropriate monomer was

sought which would permit polymerization at substan-

tially higher initial monomer concentrations. An un-

symmetrical version of monomer 2, having one propenyl

group in an ortho position and one in the para position of

the other ring, was therefore synthesized (monomer 3;

Scheme 7). The polymerization of monomer 3 in the

The proposed mechanism for the cation radical chain

cyclobutapolymerization of 2 induced by the triarylami-

Á

nium salt 1 (Scheme 6) is based upon the known

mechanism of the trans-anethole dimerization and the

theoretical considerations discussed in the introduction.

In particular, the intramolecular hole transfer shown in

step 3(a) should be strongly exergonic, given the

difference in the oxidation potentials of the trans-

anethole dimer (ca 1.6 V9) and trans-anethole (1.23 V).

Whether the hole transfer from the long bond of the

Á

presence of 10 mol% of 1 at a concentration of 0.192 M

for 8 min yielded a cyclobutapolymer having M_w=

86700 (PDI = 1.84), i.e. roughly twice the average mol-

ecular weight obtainable from the polymerization of

Á

monomer 2 using 15 mol% of 1 . The cyclobutapolymer

J. Phys. Org. Chem. 12, 808–818 (1999)

812

N. L. BAULD, D. GAO AND T. APLIN

Scheme 8. Synthesis of the Diels±Alder monomer 4

Scheme 9. Polymerization of monomer 4

Scheme 10. Cyclobutadimerization/oligomerization of monomer 4

structure was again readily conﬁrmed by proton NMR

and COSY spectra.

the cyclohexene product,¹²which can therefore be

considered the result of an indirect Diels–Alder reaction.

Further, cyclobutanation of a 1,3-pentadiene moiety

would involve a sterically unhindered (i.e. unsubstituted)

diene terminus, and therefore should proceed relatively

rapidly in comparison with addition to a terminal

propenyl moiety such as was involved in the case of

monomers 2 and 3. The monomer 4, which should exhibit

analogous chemistry to that observed for 1,3-pentadiene

and anisole, was therefore prepared (Scheme 8). The

polymerization of 4 in dichloromethane solution (0.31 M)

Indirect Diels±Alder polymerization

Diels–Alder cycloadditions to s-cis conjugated dienes are

also a well known reaction of cation radicals such as that

of trans-anethole.^1,3In the case of an acyclic diene such

as 1,3-pentadiene, the predominant conformation of the

conjugated diene linkage is s-trans, so that addition

initially occurs at least in part to yield a vinylcyclobutane

adduct.¹¹However, the latter typically rearranges rapidly

via a cation radical vinylcyclobutane rearrangement to

Á

at 0°C in the presence of 10 mol% of 1 proceeded

efﬁciently, yielding a polymer of weight average mol-

ecular weight 59000 after 10 min (Scheme 9). When the

J. Phys. Org. Chem. 12, 808–818 (1999)

CATIONIC RADICAL CHAIN CYCLOADDITION POLYMERIZATION

813

Scheme 11. Cation radical cycloaddition of trans-anethole and ortho-anethole to 4-trans-(2,4-pentadienyl)anisole

initial monomer concentration was increased to 0.37 M,

the molecular weight increased to 153000.

reaction, in fact, generated a product distribution very

similar to that observed in the polymer, with cyclobutane

linkages being formed almost exclusively initally and

persisting in substantial amounts even to high conver-

sions. Comparison of the proton NMR spectra of this

latter mixture of vinylcyclobutane and Diels–Alder

adducts with that of the polymer provided clear

conﬁrmation of the structure of poly(4) as a mixture of

these two cycloaddition modes. The percentage of acid-

catalyzed (linear) polymer linkages is negligible. As

would be expected, the propenyl and pentadienyl end-

group absorptions observed in the polymer are compar-

able to each other in amount. At low degrees of

polymerization, the cyclobutane linkages were strongly

predominant, but as the polymerization proceeded to

higher molecular weights, the percentage of Diels–Alder

linkages increased markedly. In the presence of a

relatively large amount of the aminium salt catalyst (30

mol%), the cyclobutane linkages of the polymer could be

rearranged to a predominantly Diels–Alder structure.

Further, the spectra of the crude polymers (from

polymerizations carried out to various molecular

weights), were virtually superimposable upon those of

puriﬁed polymers (chromatography) and closely corre-

sponded to (were virtually superimposable upon) the

spectra of the cycloadduct mixtures obtained in the more

appropriate model reaction.

To characterize the polymer structure and to obtain

information about the relative amounts of cyclobutane

and Diels–Alder linkages in the polymer, model

compounds for both types of polymer linkage were

prepared. First, a mixture of the cyclobutadimer (5) of 4,

along with the trimer, tetramer and lower cyclobutaoli-

Á

gomers, was prepared by reacting 4 with 1 in the

presence of excess 2,6-di(tert-butyl)pyridine (Scheme

10).¹³Interestingly, no Diels–Alder adducts were noted

in the products of this reaction, and it therefore appears

that the initial addition of the cation radical of 4 to neutral

4 occurs predominantly via the cyclobutanation mode.

Second, the model reaction of 5-anisyl-trans-1,3-penta-

Á

diene with trans-anethole in the presence of 1 was

studied (Scheme 11). Although not a perfect model of the

propenyl function of 4, which is ortho to the oxygen

function, trans-anethole is a readily available compound

the cycloadditions of which to various conjugated dienes

had already been studied. This reaction, at very short

reaction times (very low conversions), led to a mixture of

vinylcyclobutane and Diels–Alder adducts, as indicated

by GC–MS, but the conversion of the former to the latter

was fairly rapid. As a consequence, only the Diels–Alder

adduct could be isolated in pure form, and this was

apparently a single diastereoisomer (6a), that correspond-

ing to the endo addition mode. Comparison of the

500 MHz ¹H NMR spectrum of the polymer with those of

the vinylcyclobutane and Diels–Alder model compounds

then revealed that the polymer does consist of a mixture

of these two linkages (>4:1 Diels–Alder: cyclobutane),

but the relative amount of cyclobutane linkages is

substantial even at relatively high degrees of polymer-

ization.

CONCLUSION

A fundamentally new polymerization method, cation

radical chain cycloaddition polymerization, has been

proposed and demonstrated. Polymers having average

molecular weights of up to 150 000 have been obtained

under exceptionally mild thermal conditions and in short

reaction times. Both cyclobutapolymerization and indir-

ect Diels–Alder polymerization have been demonstrated.

The enhanced efﬁciency of cation radical chain poly-

merization as compared with the corresponding reactions

of monofunctional compounds appears to be based upon

The disparity between the amount of vinylcyclobutane

rearrangement in the polymer and in the model reaction

with trans-anethole appeared signiﬁcant, and prompted

the study of a model reaction which more closely

parallels the polymerization of 4, viz. the reaction of o-

propenyl anisole with 5-anisyl-1,3-pentadiene. This

J. Phys. Org. Chem. 12, 808–818 (1999)

814

N. L. BAULD, D. GAO AND T. APLIN

the efﬁciency of intramolecular hole transfer, which is

unique to the polymerization process, relative to

intermolecular hole transfer, which is involved in the

corresponding monofunctional chemistry.

phorus oxychloride at room temperature and the solution

was reﬂuxed for 1.5 h. After cooling the reaction mixture

in an ice bath, water was added slowly, followed by

dichloromethane solvent. The crude monomer 2 was

obtained by separation of the dichloromethane layer,

washing it with water and drying and evaporating the

solvent. Column chromatography on alumina (1:1

hexane–dichloromethane) gave 2.48 g (42.4%) of 2,

which was found to be at least 98% pure by GC criteria:

m.p. 175–176°C; ¹H NMR, ꢀ 1.8 (dd, 6H), 4.3 (s,4H), 6.1

(dq, 2H, J = 15.8 Hz), 6.3 (d,2H, J = 15.8 Hz), 6.8 (d,

4H), 7.3 (d, 4H); ¹³C NMR, ꢀ 8.4, 66.6, 114.7, 124.0,

EXPERIMENTAL

Analysis. Routine ¹H NMR and ¹³C NMR were recorded

on a Bruker AC250 spectrometer as solutions in CDCl₃.

1

High-ﬁeld H NMR spectra were recorded on a General

Electric GN-500 spectrometer. Chemical shifts (ꢀ) are

reported in parts per million downﬁeld from a tetra-

methylsilane reference, and coupling constants (J) are

given in Hz. Low-resolution mass spectrometry (LRMS)

was performed with a Hewlett-Packard Model 5971A

GC–MS system equipped with a DB-1 capillary column

(15 m Â 0.25 mm i.d.). High-resolution mass spectro-

metry (HRMS) was carried out on a Dupont (CEC) 21-

110B mass spectrometer. Gel permeation chromatogra-

phy (GPC) was carried out in tetrahydrofuran using a

Waters Model 550 HPLC pump, a Waters Model 410

differential refractometer, and a Waters Model 745 data

126.9, 130.2, 131.2, 157.1; LRMS, m/z 294 (M ), 164,

133 (base); HRMS, m/z calculated for C₂₀H₂₂O₂

294.1619, found 294.1613; E_p= 1.23 V vs SCE.

Polymerization of 2. To a solution of 2 (200 mg,

0.68 mmol) in dry dichloromethane (12ml) at room

temperature under

(0.1 mmol) of 1

a

nitrogen atmosphere, 80 mg

Á

were added, with stirring. After

7 min the reaction mixture was quenched with an excess

of saturated potassium carbonate in methanol. The

organic layer was washed with water (3 Â 10 ml), dried

and the solvent removed to give 230 mg of the polymer.

GC analysis of the crude product revealed the absence of

any of the starting monomer. The crude polymer was

subjected to column chromatography on alumina. The

column was ﬁrst eluted with 9:1 hexane–dichloro-

methane to remove the neutral triarylamine (1), then

with dichloromethane to elute the polymer. The NMR

specrum of the polymer (see below) was essentially

identical before and after chromatographic puriﬁcation,

except for the aromatic absorptions arising from the

presence of 1 in the crude material. The weight-average

molecular weight (M_w) of this polymer was found (GPC)

to be 9460, with a PDI of 5.30. When the same poly-

merization reaction was carried out in the presence of

excess powdered potassium carbonate for either 10 or

30 min to minimize any acid-catalyzed side reactions, the

NMR of the polymer was again identical with that

obtained in the absence of potassium carbonate. In this

case, however, the M_wwas lowered to 3700, with

PDI = 3.0.

˚

module with an Ultrastyragel 500 A column connected in

4

˚

series with a Styragel 10 A column. The GPC analyses

were calibrated with polystyrene standards.

Solvents, catalyst and reagents. Reagent-grade dichloro-

methane was distilled from phosphorus pentoxide im-

mediately prior to use. Tris(4-bromophenyl)aminium

hexachloroantimonate was used as received from Aldrich.

All other reagents used as starting materials were used as

received from Aldrich.

Synthesis of Monomer 2. 1,2-Diphenoxyethane (Al-

drich) was ﬁrst subjected to bis(propionylation by a

literature procedure.¹⁴From 15 g of 1,2-diphenoxyethane

was obtained 21 g (94%) of 1,2-bis(4-propionylphen-

1

oxy)ethane (99% purity by GC): m.p. 112–114°C; H

NMR, ꢀ 1.2 (t, 6H), 2.9 (q, 4H), 4.4 (s, 4H), 6.94 (d, 4H),

7.93 (d, 4H); ¹³C NMR, ꢀ 8.3, 31.4, 66.4, 114.2, 130.2,

133.1, 162.1, 199.4; IR (C

=

O), 1687; LRMS, m/z 326

(M ), 297, 241, 207, 177, 134, 121 (base). Reduction of

this diketone (16.7 g) with sodium borohydride (2:1

molar ratio of hydride to diketone) in a 3:1 solution of

ethanol and tetrahydrofuran for 1 h at room temperature,

followed by quenching of the reaction at 0°C with acetic

acid (10%) and extraction with dichloromethane, yielded

19 g of the corresponding diol, 1,2-bis [4-(1-hydroxy-1-

propyl)phenoxy]ethane, which was used without further

When the polymerization of 2 is carried out under the

same conditions as described above, but the reaction is

allowed to run for 10 min, the M_wis found to increase to

37000 (PDI = 7.31). The NMR spectra of this higher

molecular weight polymer is virtually identical with

those of the two lower molecular weight polymers

1

puriﬁcation: m.p. 71–72°C; H NMR, ꢀ 0.8 (t,6H), 1.6–

described above: H NMR (55°C, CDCl₃), ꢀ 1.1 (br s,

1.8 (m,4H), 1.8 (br s,2H), 4.2 (s,4H), 4.4 (t,2H), 6.8 (d,

4H), 7.2 (d,4H); ¹³C NMR, ꢀ 10.1,31.7, 66.5,72.1,114.5,

127.2,137.2, 158.0; IR(OH), 3360. Monomer 2 was

prepared by the dehydration of the preceding diol: to

6.6 g (0.02 mol) of the diol dissolved in pyridine (25 ml)

was added a slight excess (7.0 g, 0.045 mol) of phos-

methyl attached to the cyclobutane ring), 1.7 (br s, non-

benzylic methine), 2.6 (br s, benzylic methine), 4.1 (br s,

ether methylenes), 6.6–7.2 (br, aromatics); ¹³C NMR

(55°C, CDCl₃), ꢀ 18.8 (methyl group attached to CB

ring), 43.3 (non-benzylic CB carbon), 52.5 (benzylic CB

carbon), 66.8 (ether carbons), 114.8, 127.7, 136.4, 157.2.

J. Phys. Org. Chem. 12, 808–818 (1999)

CATIONIC RADICAL CHAIN CYCLOADDITION POLYMERIZATION

815

1-(2-Bromoethoxy)-2-(2-propenyl)benzene. A mixture

of 2-allylphenol (10.05 g, 0.075 mol), 1,2-dibromoethane

(28.5 g, 0.15 mol), and potassium carbonate (12.42 g,

0.09 mol) in N,N-dimethylformamide (25 ml) was stirred

at room temperature for 48 h and then subjected to

aqueous workup. Column chromatography on silica gel

(13:1 hexane–ethyl acetate) afforded the pure product

0.89 (t, 3H, J = 7.38 Hz), 1.67–1.80 (m, 2H), 1.84 (dd,

3H, J = 1.65, 6.68), 4.33 (s, 4H), 4.54 (t, 1H, J = 6.59 Hz),

6.25 (m, 1H), 6.71 (d, 1H, J = 15.87 Hz), 6.88–7.45 (m,

8H); ¹³C NMR (CDCl₃, 250 MHz), ꢀ 10.2, 18.9, 31.8,

66.6, 67.2, 75.6, 112.8, 114.6, 121.3, 125.5, 126.5, 127.2,

127.6, 137.8, 155.1, 158.1; LRMS, m/z 312 (M );

HRMS, m/z calculated for C₂₀H₂₄O₃312.172545, found

312.172533.

1

(14 g, 77.5%): H NMR (CDCl₃, 250 MHz), ꢀ 3.42 (d,

2H, J = 6.67 Hz), 3.68 (t, 2H, J = 6.11 Hz), 4.31 (t, 2H,

J = 6.11 Hz), 5.06 (dd, 2H, J = 15.2, 9.51 Hz), 6.0 (m,

1H), 6.82 (d, 1H, J = 8.2 Hz), 6.98 (d, 1H, J = 7.32 Hz),

7.18 (d, 2H, J = 7.2 Hz); LRMS, m/z 242 (M 1);

HRMS, m/z calculated for C₁₁H₁₃OBr 241.022801, found

241.022823.

The product alcohol (1.33 g, 4.26 mmol) was sus-

pended in dry dichloromethane (22 ml), followed by the

addition of dry triethylamine (1.19 ml, 8.53 mmol).

Triﬂic anhydride (0.73 ml, 4.26 mmol) was then added

all in one portion at 78°C. The reaction mixture

was stirred for 30 min at this temperature and then

quenched with dilute sodium hydrogencarbonate solu-

tion. After aqueous workup and silica gel column

chromatography (100:4 hexane–ethyl acetate), monomer

5 was obtained in pure form (330 mg, 26.4%): m.p. 112–

1-(2-Bromoethoxy)-2-(trans-1-propenyl)benzene.

A

catalytic amount of PdCl₂was added to 50 ml of

dichloromethane, followed by the addition of 30 drops

of acetonitrile. After stirring this mixture for 5 min, 14 g

(0.058 mol) of 1-(2-bromoethoxy)-2-(2-propenyl)ben-

zene were added and the solution was stirred for 40 h at

room temperature. After aqueous workup, the product

was chromatographed (silica gel column, hexane eluent),

yielding 14 g (100%) of the pure product: ¹H NMR

(CDCl₃, 250 MHz), ꢀ 1.9 (dd, 3H, J = 6.58, 1.67 Hz),

3.68 (t, 2H, J = 6.28 Hz), 4.3 (t, 2H, J = 6.27 Hz), 6.26

(m, 1H), 6.75 (d, 1H, J = 14.6 Hz), 6.8–7.4 (m, 4H);

LRMS, m/z 242 (M 1); HRMS, calculated for

C₁₁H₁₃OBr 241.022801, found 241.022461.

1

114°C; H NMR (CDCl₃, 250 MHz), ꢀ 1.84 (d, 6H,

J = 6.56), 4.32 (s, 4H), 6.10 (m, 2H), 6.34 (d, 1H,

J = 16.5 Hz), 6.68 (d, 1H, J = 15.55 Hz), 6.78–7.40 (m,

8H); ¹³C NMR (CDCl₃, 250 MHz), ꢀ 18.46, 18.95, 66.70,

67.34 112.8, 114.87, 121.36, 123.76, 126.56, 126.64,

126.96, 127.72, 130.35, 131.8, 155.2, 158.0; LRMS, m/z

294(M ); HRMS, calculated for C₂₀H₂₂O₂294.161980,

found 294.162004.

Polymerization of monomer 3. To monomer 3 (73.5 mg,

2.5 mmol) dissolved in dry dichloromethane (0.8 ml) was

added the aminium salt initiator (20.4 mg, 0.25 mmol)

dissolved in dry dichloromethane (0.5 ml; the overall

monomer concentration is 0.192 M) in one portion at 0°C.

The reaction mixture was stirred for 8 min and then

quenched using saturated potassium carbonate–methanol

solution. The crude polymer (70 mg, 95%) obtained after

aqueous workup was found (GPC) to have M_w= 86700

Synthesis of monomer 3. A solution of 4'-hydroxy-

propiophenone (Aldrich) (4.5 g, 0.03 mol), 1-(2-bromo-

ethoxy)-2-(trans-1-propenyl)benzene (this paper; 4.82 g,

0.02 mol) and potassium carbonate (4.14 g, 0.03 mol) in

N,N-dimethylformamide solution (80 ml) was stirred at

room temperature for 24 h and then subjected to aqueous

workup and silica gel chromatography (100:15 hexane–

ethyl acetate) to yield the pure product, 1-[2'-(trans-1@-

propenyl)phenoxy]-2-[4'-(1@-propionyl)phenoxy]ethane

1

(PDI = 1.837): H NMR (CDCl₃, 500 MHz), ꢀ 1.1–1.2

(br, characteristic of methyl attached to cyclobutane

ring), 1.79–1.85 (br), 2.78–2.80 (br), 4.0–4.35 (br), 6.1–

6.25 (br), 6.3–7.36 (br).

1

(3.2 g, 51%): m.p. 82–83°C; H NMR (deuteroacetone,

250 MHz), ꢀ 1.12 (t, 3H, J = 7.23 Hz), 1.78 (d, 3H,

6.61 Hz), 2.98 (q, 2H, J = 7.25 Hz), 4.40 (t, 2H,

J = 4.37 Hz), 4.51 (t, 2H, J = 4.46 Hz), 6.25 (m, 1H),

6.68 (d, 1H, J = 16.78), 6.88–8.00 (m, 8H); ¹³C NMR

(deuteroacetone, 250 MHz), ꢀ 8.2, 19.5, 31.7, 67.8, 68.0,

113.8, 115.2, 122.0, 126.2, 126.5, 128.0, 128.2, 130.9,

131.2, 156.2, 163.0, 199.0; LRMS, m/z 311 (M 1);

HRMS, m/z calculated for C₂₀H₂₃O₃311.164720, found

311.165234.

trans-2,4-Pentadienyl phenyl ether. To a suspension of

potassium carbonate (6.1 g, 0.044 mol) in 200 ml of

acetone at room temperature was added phenol (7.52 g,

0.08 mol) and then trans-2,4-pentadienyl bromide

(7.38 g, 89% pure by GC, 0.044 mol). The solution was

stirred for 24 h. Aqueous workup yielded a colorless oil,

which was puriﬁed by column chromatography (silica

gel; light petroleum eluent), giving 5.8 g (90%) of the

All of this puriﬁed product (3.2 g, 0.01 mol) was

reduced with sodium borohydride (399 mg, 0.01 mol) in

ethanol (36 ml)–tetrahydrofuran (12 ml) solvent for 5 h at

room temperature. After quenching with 10% aqueous

acetic acid followed by aqueous workup, the pure

product, 1-[2'-(trans-1@propenyl)phenoxy]-2-[4'-(1@-hy-

droxypropyl)phenoxy]ethane was obtained (3.22 g,

product:^{15 1}H NMR (250 MHz),

ꢀ 4.5 (d, 2H,

J = 5.72 Hz), 5.2–5.26 (dd, 2H, J = 14.57, J = 9.29 Hz),

5.8–5.92 (m, 1H), 6.3–6.4 (m, 2H), 6.85–6.92 (m, 3H),

7.29–7.38 (m, 2H); LRMS, m/z 160 (M ).

trans-2,4-Pentadienyl phenol. To a solution of trans-

2,4-pentadienyl phenyl ether (1.6 g, 0.01 mol) in dry

dichloromethane (100 ml) cooled to 40 to 30°C was

1

100%): m.p. 70–72°C; H NMR (CDCl₃, 250 MHz), ꢀ

J. Phys. Org. Chem. 12, 808–818 (1999)

816

N. L. BAULD, D. GAO AND T. APLIN

added boron triﬂuoride–ether complex (1.52 ml,

0.012 mol). The resulting solution was stirred for 1 h at

40 to 30°C. After aqueous workup the crude product

was chromatographed (silica gel column; 10:1 light

petroleum–ethyl acetate), yielding 1.52 g (94.5%) of the

pure product:^{15 1}H NMR (250 MHz), ꢀ 3.32, (d, 2H,

J = 6.84 Hz), 4.92–5.10 (dd, 2H, J = 16.09, 9.18 Hz), 5.8

(m, 1H), 6.08 (m, 1H), 6.3 (m, 1H), 6.75 (d, 2H,

J = 8.52 Hz), 7.0 (d, 2H, J = 8.46 Hz); LRMS, m/z 160

113.829, 115.525, 129.484, 131.716, 132.056, 133.899,

136.935, 157.982; HRMS (CI), m/z calculated for

C₁₂H₁₅O 175.1123, found 175.1114.

Diels±Alder adduct (6a) of trans-anethole and methyl

4-(trans-2',4'-pentadienyl)phenyl ether. To a solution of

trans-anethole (74.1 mg, 0.5 mmol) and methyl 4-(trans-

2,4-pentadienyl)phenyl ether (87 mg, 0.5 mmol) in dry

dichloromethane (1 ml) at 0°C was added tris(4-

bromophenyl)aminium hexachloroantimonate (41 mg,

0.05 mmol) dissolved in 1 ml of dry dichloromethane

dropwise over a period of 30 s. The reaction mixture was

stirred for 7 min and then quenched with excess saturated

potassium carbonate–methanol. Aqueous workup and

column chromatography (silica gel, 100:1 hexane–ethyl

acetate) gave 45 mg (28%) of the pure product: ¹H NMR

(500 MHz), ꢀ 0.92 (d, 3H, methyl, J = 6.62 Hz), 1.74–

1.82 (m, 2H, H6), 2.09–2.15 (m, 1H, H5), 2.26–2.32 (m,

2H, benzylic methylene), 2.45–2.49 (m, 1H, H3), 2.69–

2.72 (dd, 1H, J = 9.03, 5.02 Hz, H4), 3.74 (s, 3H,

—OCH₃), 3.8 (s, 3H, —OCH₃), 5.48–5.53 (m, 1H, H2),

5.63–5.68 (m, 1H, H1), 6.72 (d, 2H, J = 6.62 Hz), 6.84–

6.87 (dd, 4H, J = 6.02, 5.82 Hz), 7.12 (d, 2H, J = 6.02).

Chemical shifts of protons were assigned from H–H

COSY spectra. Speciﬁcally, irradiation of the signal

corresponding to the benzylic methylene protons en-

gendered an intensity increase of 5.11% in the signal

corresponding to the proton at C5, whereas the C4 proton

signal did not show an NOE effect. Similarly, irradiating

the C5 methyl signal caused a small intensity increase in

the C4 proton (1.9%) and C3 (1.08%) proton signals and

had no effect on the C3 proton signal. These observations

indicate that the C5 methyl and the C4 and C3 protons are

all cis. This corresponds to a net endo Diels–Alder

addition with suprafacial addition to the dienophile. ¹³C

NMR (250 MHz), ꢀ 20.786 (CH₃), 28.513 (C6), 33.209

(C5), 37.069 (benzylic methylene carbon), 41.134 (C3),

49.811 (C4), 55.179 (— OCH₃), 55.246 (— OCH₃),

113.310, 113.407, 126.023 (C1), 127.718 (C2), 129.907,

130.266, 130.675, 133.073, 157.574, 157.675. The

stereochemistry was assigned by NOESY spectra; HRMS

m/z calculated for C₂₂H₂₆O₂322.193280, found,

322.193684.

(M ).

1-[4'-trans-2@,4@-Pentadienyl)phenoxy]-2-[2'-trans-1@-

propenyl)phenoxy]ethane (4). To 30 ml of N,N-di-

methylformamide at room temperature were added

2.19 g (0.0159 mol) of potassium carbonate and 2.13 g

(0.0133 mol) of 4-(trans-2,4-pentadienyl)phenol. After

stirring the mixture for 30 min, 3.83 g (0.00158 mol) of

1-(2-bromoethoxy)-2-(trans-1-propenyl)benzene were

added and the reaction mixture was stirred for an

additional 43 h. Aqueous workup and silica gel chroma-

tography (light petroleum, then 100:1 light petroleum–

ethyl acetate) yielded the pure monomer 6 (2.8 g, 66%):

m.p. 58°C; ¹H NMR (500 MHz), ꢀ 1.87 (d, 3H,

J = 6.68 Hz), 3.40 (d, 2H, J = 6.75 Hz), 4.33 (m, 4H),

5.00–5.14 (dd, 2H, J = 16.65, 10.18 Hz), 5.80–5.86

(m, 1H, —CH₂CH

1H, —CH₂CH CHCH

J = 15.85 Hz (d), 6.63 (q) —CH

[dt, 1H, J = 17.06 Hz (d), 10.34 (t), —CH₂CH

CHCH CH₂], 6.70–6.72 (d, 1H, J = 15.93 Hz,

—CH

CHCH₃), 6.9–7.40 (8H, m); ¹³C NMR (500

=

CHCH

CH₂), 6.19–6.27 [dq, 1H,

CHCH₃], 6.29–6.37

=CH₂), 6.06–6.15 (m,

=

MHz, CDCl₃), ꢀ 18.85 (CH₃), 38.01 (CH₂), 66.7, 67.3

(—OCH₂CH₂O), 112.6 (Ar-C), 114.8 (Ar-C), 115.6

(—CH₂CH

(—CH CHCH₃), 126.44 (—CH

(Ar-C), 127.65 (Ar-C), 129.6 (Ar-C), 131.8 (—CH₂CH

=

CHCH=

CH₂), 121.3 (Ar-C), 125.6

=

CHCH₃), 126.54

=CHCH=CH₂), 132.6 (Ar-C), 133.8 (—CH₂CH

=CHCH

=

CH₂), 137.0 (—CH₂CH CHCH CH₂),

=

155.25 (Ar-C), 157.2 (Ar-C); HRMS (CI), m/z calculated

for C₂₂H₂₄O₂320.1776, found 320.1773. Positional

assignments of chemical shifts are based upon H–H

COSY and C–H correlation spectra.

Methyl 4-(trans-2',4'-pentadienyl)phenyl ether. To 4-

(trans-2',4'-pentadienyl)phenol (1.27 g, 7.94 mmol) in

N,N-dimethylformamide (30 ml) at room temperature

was added 1.1 g (7.97 mmol) of potassium carbonate and

the solution was stirred for 30 min. An excess of methyl

iodide (0.5 ml) was then added and the reaction mixture

was stirred for an additional 3 h. After an aqueous

workup, silica gel column chromatography (light petro-

leum) yielded the product (0.9 g, 65.2%): ¹H NMR

(250 MHz), ꢀ 3.39 (d, 2H, J = 6.77 Hz), 3.79 (s, 3H), 5.00

(d, 1H, J = 10.14 Hz), 5.10 (d, 1H, J = 16.99 Hz), 5.82

(m, 1H), 6.10 (m, 1H), 6.35 (m, 1H), 6.82 (d, 2H,

J = 8.63 Hz), 7.10 (d, 2H, J = 8.47 Hz); ¹³C NMR

(250 MHz, CDCl₃), ꢀ 37.973 (CH₂), 55.230 (—OCH₃),

Cyclobutane and Diels±Alder adducts of 2-(trans-1'-

propenyl)anisole with methyl 4-(trans-2',4'-pentadie-

nyl)phenyl ether. To a solution of 2-(trans-1'-propenyl)

anisole (148.2 mg, 1 mmol) and methyl 4-(trans-2',4'-

pentadienyl)phenyl ether (174 mg, 1 mmol) in dichloro-

methane (2 ml) at 0°C was added, in one portion, tris(4-

bromophenyl)aminium hexachloroantimonate (82 mg,

0.1 mmol) in dichloromethane (2 ml). After stirring the

reaction mixture for 10 min at 0°C, a quenching solution

of saturated K₂CO₃in methanol was added. Aqueous

workup and column chromatography (silica gel: ﬁrst

hexane then 1000:5 hexane–ethyl acetate) yielded a 1:1

mixture of cyclobutane and Diels–Alder adducts (52 mg,

J. Phys. Org. Chem. 12, 808–818 (1999)

CATIONIC RADICAL CHAIN CYCLOADDITION POLYMERIZATION

817

16.2%): ¹H NMR (500 MHz, CDCl₃, chemical shift

assignments via H–H COSY spectra): Diels–Alder

adducts: ꢀ 0.908 [minor DA adduct (33%); d, 3H,

J = 7.03, 0.932 (major DA adduct (67%); d, 3H,

J = 6.624), 1.78–1.86 (m, 2H, H6), 2.15–2.22 (m, 1H,

H5), 2.24–2.29 (m, 2H, benzylic protons), 2.27–2.32 (m,

1H, H3), 2.57–2.62 (m, 1H, H4), 3.75 (3H, s), 3.80

(3H,s), 5.52–5.56 (m, 1H, H2), 5.64–5.68 (m, 1H, H1),

6.72–7.26 (m, 8H). Cyclobutane adduct: ꢀ 1.1 (d, 3H,

J = 6.22), 1.37–1.44 (m, 1H, H4), 2.21–2.25 (m, 2H, H3,

H4), 2.75–2.82 (m, 1H, H1), 3.10 (t, 1H, H2, J = 8.23–

9.03), 3.24 (d, 1H, J = 6.63, a diastereotopic benzylic

methylene); 3.38 (d, 1H, J = 6.62, the other diastereo-

topic methylene), 3.74 (3H, s), 3.77 (3H, s), 5.48 (m, 1H,

vinyl proton distal to CB ring), 5.62 (m, 1H, vinyl proton

proximal to CB ring), 6.72–7.26 (m, 8H); HRMS, m/z

calculated for C₂₂H₂₆O₂322.193280, found: 322.192844.

(—CH

=CHCH₃), 126.9, 127.3, 127.7 (—CH₂CH=

CH—CB ring), 127.8, 129.5, 129.6, 131.9

(—CH₂CH

ring), 137.0 (—CH₂CH

=

CHCH

=

CH₂), 133.2, 132.4, 133.8,

CH₂), 135.4 (—CH₂CH CH-CB

CHCH CH₂), 155.23, 156.58,

=CHCH

=

156.93, 157.14.

Polymerization of monomer 4 to M_W59300. To

200 mg (0.626 mmol) of 4 dissolved in 1 ml of dry

dichloromethane were added, in a dropwise fashion over

a 1 min period, 51 mg (0.0625 mol) of 1 in 1 ml of dry

dichloromethane. The reaction mixture was stirred for

10 min and then quenched with saturated K₂CO₃–

CH₃OH. The crude polymer obtained after aqueous

workup had M_W= 59300 (PDI = 1.75). After column

Á

1

chromatography, the H NMR spectrum was essentially

unchanged. The 500 MHz ¹H NMR spectrum revealed an

8:2 ratio of DA:CB linkages. ¹H NMR (500 MHz,

CDCl₃, chemical shift assignments via comparison with

the model Diels–Alder compound), ꢀ 0.9 (d, 3H,

J = 6.62), 1.67–1.76 (m, 2H, H6), 1.80–1.89 (propenyl

methyl end groups), 2.14–2.17 (m, 1H, H5), 2.18–2.23

(m, 2H, benzylic protons), 2.42–2.46 (m, 1H, H3), 2.60–

2.65 (m, 1H, H4), 3.85–4.40 (br, ether methelenes), 4.9

(d, 1H, J = 9.63), 5.10 (d, 1H, J = 16.46), 5.45–5.51 (m,

1H, H₂), 5.60–5.67 (m, 1H, H₁), 5.76–5.86 (m, 1H), 6.03–

6.12 (m, 1H), 6.18–6.26 (m, 1H), 6.27–6.37 (m, 1H),

6.63–6.80 (m, 1H), 6.83–7.40 (brm, 16H).

Oligomerization of monomer 4 in the presence of a

hindered base to form 5. To 200 mg (0.625 mmol) of 4

dissolved in dry dichloromethane (2 ml) was added 2,6-

di-tert-butylpyridine (74 mg, 0.375 mmol) followed by

Á

addition of 255 mg of 1 (0.313 mmol) in dry dichloro-

methane (4 ml) over a 2 min period. The reaction mixture

was stirred for 15 min and quenched by the addition of

saturated K₂CO₃–CH₃OH solution. After aqueous work-

up and column chromatography (alumina), 42 mg (21%)

of the trimer–oligomer mixture (7) were obtained: GPC

M_W1130 (PDI = 1.027); oligomer M_W8080

(PDI = 2.43); ¹H NMR (500 MHz, CDCl₃, chemical shift

assignments via H–H COSY spectra), ꢀ 1.10 [d, 3H,

J = 6.02, methyl attached to a CB ring], 1.41 (m, 1H, one

of the CH₂protons of the CB ring), 1.86 (d, J = 6.42 Hz,

CH₃of propenyl end group), 2.22 (m, 1H, methine on

methyl-bearing CB carbon), 2.22 (m, 1H, one of CB

methylene protons), 2.86 (m, 1H, allylic methine on the

CB ring), 3.14 (t, 1H, J = 8.94–9.23 Hz, benzylic

methine), 3.22 (d, 1H, J = 6.62 Hz, one of the diaster-

eotopic benzylic methylenes), 3.36 (d, 1H, J = 6.63 Hz,

the other diastereotopic benzylic methylene), 4.28–4.36

(m, 8H, ether methylenes), 5.00–5.19 (dd, 2H, J = 17.06,

Polymerization of monomer 4 to M_W= 153000. To

300 mg (0.932 mmol) of 4 dissolved in 1.5 ml of dry

dichloromethane was added, in a dropwise fashion over a

1 min period, a solution of 77 mg (0.0932 mol) of 1 in

1.0 ml of dry dichloromethane. After stirring the reaction

mixture for 4 min at 0°C, the mixture was quenched with

saturated K₂CO₃–CH₃OH. Following aqueous workup,

the polymeric product was found to have M_W= 153 500

(PDI = 3.58).

Á

Polymerization of monomer 4 to the predominantly

Diels±Alder polymer. To 100 mg (0.313 mmol) of 4 in

2.0 ml of dry dichloromethane were added, in a dropwise

fashion over 8 min, 78 mg (0.0939 mmol) of 1 in 8.0 ml

of dry dichloromethane. The reaction mixture was stirred

for 20 min and then quenched with K₂CO₃–CH₃OH

solution, followed by aqueous workup. The polymer was

found to have M_W= 173 000 (PDI = 1.59). The 500 MHz

¹H NMR spectrum corresponded very closely to those of

the Diels–Alder model compounds.

10.04 Hz, C

=CH₂of pentadienyl end groups), 5.50 (m,

Á

1H, vinyl proton off the CB ring), 5.63 (dd, 1H, J = 15.25,

6.42 Hz, vinyl proton nearest the CB ring), 5.83 (m, 1H,

pentadienyl end groups), 6.10 (dd, 1H, J = 14.65,

13.25 Hz, pentadienyl end group), 6.25 (m, 1H, propenyl

end groups), 6.35 (m, 1H, pentadienyl end group), 6.72

(d, 1H, J = 15.93 Hz, propenyl end group), 6.80–7.50 (m,

16H, aryl); ¹³C NMR (500 MHz; chemical shifts assigned

with the assistance of C–H correlation spectra), ꢀ 19 (end

group CH₃), 21 (CH₃attached to CB), 33.6 (CB

methylene), 35 (CB methine attached to CH₃), 37.8

(end group benzyl), 38.0 (benzyl attached to vinyl), 41.0

(CB methine attached to vinyl), 49.2 (CB methine

attached to aryl), 63.5–63.9 (ether methylenes), 111.5,

Acknowledgements

The authors thank the National Science Foundation

(CHE-9610227) and the Robert A. Welch Foundation (F-

149) for support of this research.

112.8, 114.9, 115.0, 115.8 (—CH₂CH

=

CHCH=

CH₂), 121.0, 121.3, 125.7 (—CH=CHCH₃), 126.7

J. Phys. Org. Chem. 12, 808–818 (1999)

818

N. L. BAULD, D. GAO AND T. APLIN

9. B.K. Marsh and N. L. Bauld, unpublished results.

REFERENCES

10. M. P. Stevens, Polymer Chemistry, 2nd edn, p. 339. Oxford

University Press, New York (1990).

11. D. W. Reynolds and N. L. Bauld, Tetrahedron 42, 6189–6194

(1986).

12. D. W. Reynolds, B. Harirchian, H.-S. Chiou, B. K. Marsh and N. L.

Bauld, J. Phys. Org. Chem. 2, 57–88 (1989).

13. P. G. Gassman and D. A. Singleton, J. Am. Chem. Soc. 106, 7993

(1984); K. T. Lorenz and N. L. Bauld, J. Am. Chem. Soc. 109, 1157

(1987).

14. N. P. Bu-Hoi, N. D. Xuong and D. Lavit, J. Chem. Soc. 1034

(1954).

15. K. Maruyama, N. Nagai and Y. Naruta, Tetrahedron Lett. 5149–

5152 (1985).

1. N. L. Bauld, in Advances in Electron Transfer Chemistry, edited by

P. S. Mariano, Vol. 2, pp. 1–66 (1992).

2. K. T. Lorenz and N. L. Bauld, J. Am. Chem. Soc. 109, 1157–1160

(1987).

3. N. L. Bauld, Tetrahedron 45, 5307–5363 (1989).

4. M. P. Stevens, Polymer Chemistry, 2nd edn, p. 15. Oxford

University Press, New York (1990).

5. R. A. Pabon and N. L. Bauld, J. Am. Chem. Soc. 105, 633–634

(1983).

6. R. A. Pabon and N. L. Bauld, J. Am. Chem. Soc. 106, 1145–1146

(1984).

7. J. T. Aplin, Dissertation, University of Texas at Austin (1997).

8. N. L. Bauld, J. T. Aplin, W. Yueh, H. Sarker and D. J. Bellville,

Macromolecules 29, 3661–3662 (1996).

J. Phys. Org. Chem. 12, 808–818 (1999)

Article Doi

Cation radical chain cycloaddition polymerization: A fundamentally new polymerization mechanism

DOI: 10.1002/(SICI)1099-1395(199911)12:11<808::AID-POC207>3.0.CO;2-M

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