NMR-Spectroscopic Investigations of Potentially Planarized Nonafulvenes

¹H- and ¹³C-NMR spectra of nonafulvene 1e and nonafulvenes 2 and 3 have been assigned, high-resolution ¹H-NMR spectra of 2 (600 MHz, Fig. 3) and of 3 (400 MHz, Fig. 2) have been analyzed, and the data are compared with those of other nonafulvenes (Tables 1–6). Generally speaking, according to their spectroscopic behavior, four classes of nonafulvenes (A–D) may be distinguished (Fig. 1). The investigation shows that compounds 1e and 3 belong to class A, being characterized by ¹H-chemical shifts around 6 ppm, strongly alternating ³J(H,H) and ¹³C chemical shifts in the range of 123 to 130 ppm, thus existing in the olefinic form with a non-planar nine-membered ring. On the other hand, 2 is the first nonafulvene of class D, being characterized by ¹H chemical shifts in the aromatic range, large ³J(H,H) values of the same size, and ¹³C chemical shifts around 110 ppm. Since NMR parameters are virtually not influenced by temperature (?50° to 50°) or solvents, it is concluded that 2 exclusively exists in the dipolar structure 2 ^± with a planarized nine-membered ring. According to Fig. 4, these classes (and their spectroscopic data) are linked by 10,10-bis(dimethylamino)nonafulvene ( 1c ; and its temperature-dependent NMR parameters): for 1c , a temperature-dependent equilibrium 1c?1c ^± had earlier been established.     

Synthetic Attempts towards ‘Aromatic’ Nonafulvenes

According to their spectroscopic behavior, four classes of nonafulvenes may be distinguished, but, so far, only three classes have been identified. Type-A nonafulvenes (including parent 1a ) are typically olefinic molecules with strongly alternating bond lengths and a nonplanar nine-membered ring. Type-B nonafulvenes are characterized by four pairs of equivalent ring H-atoms and ring C-atoms. Spectra of both Type-A and Type-B nonafulvenes are not dependent on temperature and solvent polarity. However, spectra of Type-C nonafulvenes (including prototype 1d with R¹ = R² = NMe₂) are strongly influenced by temperature and solvent polarity due to an equilibrium 1?1 ^± between the nonpolar olefinic 1 and dipolar planarized 1 ^±. So far, Type-D nonafulvenes occurring exclusively in the dipolar form 1 ^± were unknown. Synthetic attempts towards nonafulvenes of Type D are described and problems encountered in nonafulvene syntheses are discussed. Several new cyclononatetraenes and four new nonafulvenes (or nonafulvalenes) 31, 1n, 3 , and 5 have been synthesized. Spectroscopic evidence shows that 11,12-bis(diethylamino)nonatriafulvalene 5 is the first Type-D nonafulvene.     

Conformational Analysis of Marine Polyhalogenated β-Chamigrenes Through Temperature-Dependent NMR Spectra

Temperature-dependent ¹H- and ¹³C-NMR spectra reveal that polyhalogenated marine β-chamigrenes or synthetic derivatives thereof which are trans-diequatorially, substituted at C(8) and C(9), such as rogiolol ((?)- 2 ), obtusol ((+)- 3 ), and their acetates (+)- 1 and (?)- 4 , undergo slow ring- A chair-chair inversion. Conformational equilibria and kinetics are investigated with the aid of synthetic model compounds and molecular-mechanics calculations. Thus, steric repulsions between Br_ax–C(2) and H_eq–C(7) are seen to disfavour thermodynamically conformers 1b , 2b , 3b , and 4b , which can only be detected through cross-saturation transfer, while additional steric repulsions between Me_ax–C(1) and OH_ax–C(3) make conformer 8b of obtusol epimer so scarcely populated that it can not be detected. In agreement, with (+)- 9 and (+)- 10 , which have a trigonal C(2), two conformers can be directly observed by NMR. The kinetic barriers, which are seen to arise mainly from steric repulsions between H_ax–C(14) and the axial H or halogen atoms at C(8) and C(10), are calculated and discussed with respect to well documented exocycliemethylidene-substituted cyclohexane(ene) systems. This helps to rationalize why in rogiolol acetate ((+)- 1 ) ring B is unusually inert towards Zn/Et₂O/AcOH which causes bromohydrine-group elimination from ring A.     

1H- und 13C-NMR.-Spektren von 6-(p-X-Phenyl)fulvenen. Kurzmitteilung

¹H- and ¹³C-NMR.-spectra of 6-(p-X-phenyl)fulvenes The ¹H- and ¹³C-NMR.-spectra of a series of 6-(p-X-phenyl)fulvenes 3 , measured at 9.39 T (93.9 kgauss), have been analyzed. In these compounds, electronic effects due to the substituent X clearly exert changes in chemical shifts as well as in coupling constants in the 5-membered ring. Small changes in bond length are observed by comparison of the vicinal ¹H, ¹H-coupling constants, whereas changes in charge densities linearly influence the chemical shifts of C(5), C(2) and C(3).     

1H-and 13C-NMR Investigation of Pentafulvenes

¹H- and ¹³C-NMR spectra of a series of 6-(p-X-phenyl)pentafulvenes 1 – 9 as well as of 6-R-substituted and 6,6-R¹,R²-disubstituted pentafulvenes 10 – 23 have been analysed. It turns out that the π-system of pentafulvenes is an attractive probe for the investigation of electronic substituent effects. Changes of vicinal H,H-coupling constants with increasing electron-donating capacity of the substituents X and R are interpreted in terms of an increasing π delocalisation in the 5-membered ring, and linear correlations of Hammett Substituent constants σ or MNDO-calculated C–C bond lengths and ³J values are observed. On the other hand, a systematic high-field shift of ₁₃C chemical shifts of the ring C-atoms is induced by electron-releasing substituents R and X, which decreases in the series C(5) > C(2)/C(3) > C(1)/C(4), and which mainly reflects changes in π-charge density.     

Über die Temperaturabhängigkeit der 13C-NMR.-Spektren von [5–6-η-(1Z, 5E)-Cyclooctadien]tetracarbonyleisen und (1Z, 5E)-Cyclooctadien

On the Temperature Dependence of the ¹³C-NMR. Spectra of [5-6-η-(1Z,5E)-Cyclooctadien] and of (lZ, 5E)-Cyclooctadiene The activation parameters of the conformational ring inversion process (simultaneous rotation around the C(3), C(4) and C(7), C(8) bonds; cf. Scheme 1) of the title compounds ( 1 and 2 , respectively) have been determined between 275 L and 155 K by a complete line shape analysis of the temperature dependent proton noise-modulated decoupled ¹³C-NMR. spectra of 1 and 2 . The temperature dependence of the rates (k( 1 ) and k( 2 ), respectively) of the inversion process can be described by the following equations (no influence of the solvents was observed; E_a in J/mol): . Further data are given in Tables 1 and 2. The carbonyl groups of the complex 1 show at 180 K , where the ring inversion process is frozen out, a single line at 211 ppm, i. e. the coalescence temperature of the carbonyl groups must be < 180 K .     

Substituent Effects on π‐Bond Delocalization of Fulvenes and Fulvalenes. Are Fulvenes Aromatic?

The influence of exocyclic substituents on π‐delocalization of pentafulvenes 2 , heptafulvenes 3 , and nonafulvenes 4 has been investigated. Pentafulvenes 2 : Changes of bond lengths (induced by exocyclic substituents R¹ and R² of 2 ) are reflected by systematic changes of ³J(H,H) (Fig. 2) as well as of ¹J(C,C) coupling constants (Fig. 4), so that linear correlations of σ_p⁺ vs. ³J(H,H) and ¹J(C,C) coupling constants were obtained. Plots of that type are very useful for determining the extent of π‐delocalization of various pentafulvalenes 5 – 8 (Figs. 6 and 12). Charge density effects of pentafulvenes and pentafulvalenes were observed by substituent‐induced shifts of the ring C‐atoms (Fig. 5). Heptafulvenes 3 : Contrary to planar pentafulvenes, heptafulvenes did not show any linear correlations of σ_p⁺ vs. ³J(H,H)‐plots (Fig. 8) or σ_p⁺ vs. δ(¹³C)‐plots (Fig. 9), although substituents R¹, R² clearly influenced ³J(H,H)‐coupling constants as well as ¹³C chemical shifts of the ring H‐atoms and ring C‐atoms. In the NMR spectra of ‘heptafulvenes with inverse ring polarization’ (in the lower range of Fig. 8), ³J(H,H)‐coupling constants were strongly alternating and were barely influenced by exocyclic substituents. This supported a boat conformation of the corresponding heptafulvenes. In the range of Hammett σ_p⁺‐values above ?0.5 to 0, strong substituent effects started to be effective, and a nearly linear approach of ³J(H,H)‐coupling constants J(2,3)/J(4,5) and J(3,4) was observed. This meant that, as soon as heptafulvenes were planar or nearly planar, there existed similar substituent effects as for planar pentafulvenes. – A similar ‘turning point’ was observed in plots of σ_p⁺ vs. ¹³C‐chemical shifts around σ_p⁺=0 (Fig. 9): In the range of strong electron‐accepting groups (above σ_p⁺=1), there was a marked substituent‐induced high‐frequency shift which strongly decreased in the series C(7)>C(2)/C(5)>C(3)/C(4), while C(1)/C(6) was barely influenced. Nonafulvenes 4 : Most nonafulvenes are non‐planar olefins with strongly alternating vicinal H,H‐coupling constants. This has been convincingly shown by the high‐resolution ¹H‐NMR spectrum of 10‐dimethylaminononafulvene ( 4c , Fig. 10), which was not planar but contained a nearly planar (E)‐dienamine substructure of the segment C(7)?C(8)? C(9)?C(10)? NMe₂ according to the NMR data. Only with very strong π‐donors (like two dimethylamino groups in 4b ), planarization of the nine‐membered ring could be observed at low temperatures (Fig. 10). Finally, the first stable nonatriafulvalene (11,12‐bis(diethylamino)nonatriafulvalene ( 10 )) existed in the planar dipolar form in the whole temperature range and even in unpolar solvents.     

NMR Study of the Steric and Electronic Structure of 2-(2-Acylethenyl)pyrroles

According to the ¹H and ¹³C NMR data, 2-(2-acylethenyl)- and 2-(2-acyl-1-phenylethenyl)pyrroles in chloroform exist exclusively in the keto form. The Z isomers of these compounds are characterized by coplanar arrangement of the olefinic fragment, carbonyl group, and pyrrole ring. The strong intramolecular hydrogen bond NÄH···O is responsible for the presence of only one rotamer. The corresponding E isomers give rise to equilibrium between conformers with syn and anti arrangement of the olefinic fragment with respect to the pyrrole ring. A very strong conjugation between the ketovinyl group and the pyrrole ring is likely to arise from an appreciable contribution of the zwitterionic structure.     

Substituenteneffekte auf die NMR-Spektren von Pentafulvenen. (13C, 13C)-NMR-Kopplungskonstanten (1J(C,C))

Substituent Effects on NMR Spectra of Pentafulvenes. ¹³C, ¹³C-NMR Coupling Constants (¹J(C, C)) ¹H- and ¹³C-NMR spectra of 6-monosubstituted pentafulvenes 1 – 8 have been analysed, and ¹J(C, C) coupling constants have been determined from ID-inadequate spectra of ¹³C satellites. It turns out that ¹³C,¹³C coupling constants of the ring C-atoms, and especially J(1,2)/J(3,4) and J(2,3), reflect the extent of π delocalisation in the fulvene ring. With increasing electron-donating capacity of the substituent R, J(1,2)/J(3,4) values are decreasing, while J(2,3) (and J(1,5)/J(4,5) as well) are increasing, and linear correlations of Hammett substituent constants σ⁺ and ¹J(C,C) values are obtained.     

Nonapentafulvalen

Nonapentafulvalene ( 1 ) has been prepared by oxidative coupling of sodium cyclopentadienide ( 6 ) and sodium cyclononatetraenide ( 7 ) with CuCl₂ in THF, two-fold deprotonation of cyclopentadienyl-cyclononatetraene 8 to give dianion 16 , and oxidative treatment of 16 with CuCl₂ (Schemes 2 and 3). Compound 1 is a highly reactive and thermally instable molecule, since valence isomerisation 1 → 17 proceeds easily even at low temperature (the half-life of 1 is ca. 30 min at ?15° in CDCl₃). NMR investigations show that nonapentafulvalene is an olefinic molecule with strongly alternating bond lengths, its nine-membered ring deviating strongly from planarity. Comparison of the NMR data of 1 with those of a series of sterically similar pentafulvenes 18 and nonafulvenes 19 (Tables 1 and 2) demonstrates that (a) with regard to the pentafulvene unit of 1 , the cyclononatetraene ring acts as very weak electron-donating group, while (b) with regard to the nonafulvene unit of 1 , the cyclopentadiene ring acts as weak electron-accepting group. So nonapentafulvalene may be regarded as a ‘nonafulvene of inverse π-polarisation’.     

1H- and 13C-NMR Investigations of Heptafulvenes

¹H- and ¹³C-NMR spectra of a series of 8-R¹-substituted as well as of 8,8-R¹, R²-disubstituted heptafulvenes, varying from inversely polarized ( 3l ) to unpolar ( 3h ) and polar heptafulvenes with electron-withdrawing groups ( 3d , e , f ), have been analyzed and compared with those of methoxytropylium salt 5a . The results concerning ³J (H,H) values and ¹³C-chemical shifts are shown in Figs. 5 and 6. It turns out that all the NMR parameters are strongly influenced by substituents R¹, R², but contrary to planar pentafulvenes, no linear correlations of the NMR parameter vs. Hammett substituent constant σ⁺ are obtained in the series 3l → 3d . ³J coupling constants J(2,3)/J(4,5) and J(3,4) are not much influenced by substituent changes in the series 3l → 3h , but are approaching in the row 3h → 3d . Similarly, signals of the ¹³C-atoms undergo a moderate shift to higher frequencies in the row 3l → 3h , but are strongly influenced by ? M groups, whereby the sensitivity is decreasing in the series C(7) > C(2)/C(5) > C(3)/C(4) > C(1)/C(6). These results are essentially explained by a boat conformation of inversely polarized heptafulvenes of the type 3l and an increasing planarization of the ring on going to polar heptafulvenes of type 3d .     

Zur Kenntnis des Chinoiden Zustandes—XX: 13CMR-Untersuchungen an Cyclohexadienonen

The ¹³C-NMR-chemical shifts of 19 para- and 5 ortho-cyclohexadienones are determined by ¹³C-Fourier-transformation spectroscopy and assigned. The effect of substituents on the chemical shift of the ring carbon atoms is discussed. The mutual dependence of the shifts of the olefinic ring carbons and the allylic carbon atom in the para-quinolid ring system is shown by computing regression lines. A frequently observed correlation between ¹³C-NMR and ¹H-NMR is examined in the case of cyclohexadienones.     

Characterization of mechanically sheared ethylene–propylene copolymers by high resolution NMR

We report high-resolution solution-state NMR experiments on chain ends generated in ethylene–propylene copolymers by mechanical shearing in an extruder. The use of the higher resolution of the ¹³C-NMR spectrum, in a two-dimensional ¹H-¹³C chemical shift correlation experiment, has allowed the complete resolution and assignment of the olefinic chain-end region of the ¹H-NMR spectrum. Simultaneously, the assignments of the ¹³C olefinic resonances, previously identified [A. C. Kolbert, J. G. Didier, and L. Xu, Macromolecules, 29 , 8591 (1996)] are confirmed. An iterative method for calculating the average molecular weight, based on quantitative measurements of the olefinic ¹H-NMR peak intensities is introduced and these results are compared with measurements from ¹³C-NMR and size exclusion chromatography and correlated to reduced viscosities. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1955–1961, 1997     

Ringtransformationen von 3-substituiertem 5-Trifluormethyl-1,3,4-thiadiazol-2(3H)-on mit Nucleophilen

Ring Transformations of 3-Substituted 5-Trifluoromethyl-1,3,4-thiadiazol-2(3H)-one with Nucleophiles The 3-chlormethyl-5-trifluoromethyl-1,3,4-thiadiazolone 3 undergoes a ring transformation to 3-acylated 2,3-dihydro-1,3,4-thiadiazoles 4 with many nucleophiles. Upon formal replacement of the chloromethyl group in the 3-position of 3 by an extended bromoalkyl chain (→9a-c) , the reaction with nucleophiles yields 4-acylated 5,6-dihydro-4H-1,3,4-thiadiazines 10 (from 9a ), 4,5,6,7-tetrahydrothiadiazepines 13 (from 9b ) and 5,6,7,8-tetrahydro-4H-1,3,4-thiadiazocines 14 (from 9c ) by ring enlargement. The 3-propargyl-thiadiazolone 17 rearranges with nucleophiles to 4-acylated 6-methylidene-5,6-dihydro-4H-1,3,4-thiadiazines 18 . The structures of the new compounds were elucidated by ¹H- and ¹³C-NMR spectroscopy.     

Novel Copolymers of Trisubstituted Ethylenes and Styrene. 7. Dihalogen Ring-Substituted Ethyl 2-Cyano-1-oxo-3-phenyl-2-propenylcarbamates

Electrophilic trisubstituted ethylenes, dihalogen ring-substituted ethyl 2-cyano-1-oxo-3-phenyl-2-propenylcarbamates, RC₆H₃ CH = C(CN)CONHCO₂C₂H₅(where R is 2,3-diCl, 2,4-diCl, 2,6-diCl, 3,4-diCl, 3,5-diCl, and 2-Cl-6-F, were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and N-cyanoacetylurethane, and characterized by CHN analysis, IR, ¹H- and ¹³C-NMR. All the ethylenes were copolymerized with styrene (M₁) in solution with radical initiation (ABCN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, ¹H- and ¹³C-NMR. The order of relative reactivity (1/r ₁) for the monomers 2,4-diCl (4.4) > 2,6-diCl (3.6) > 2,3-diCl (3.4) = 3,4-diCl (3.4) > 2-Cl-6-F (2.7) > 3,5-diCl (2.0). High T _g of the copolymers in comparison with that of polystyrene indicates decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene structural unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in 270–420°C with residue (5–13% wt), which then decomposed in the 420–650°C range.     

PHYTOCHROME MODELS: PART 10. CONCENTRATION,SONICATION AND TEMPERATURE AFFECTING THE POPULATION OF THE GROUND-STATE CONFORMERS OF BILIVERDIN DIMETHYL ESTER IN SOLUTION*

UV-vis absorption and fluorescence spectroscopy were used to show that in alcoholic solutions (methanol, ethanol, 2-methylbutan-1-ol, and 2-octanol) concentration, temperature, and sonication affect the relative populations of the more rigid stretched and the more flexible helically coiled conformers of biliverdin dimethyl ester. In aromatic solvents, e.g. toluene, no such effects could be detected. At concentrations larger than 3 10^-5M in the alcoholic solvents aggregates and monomeric coiled species prevail. Upon dilution, the fraction of stretched monomeric conformers increases. Heating and sonication at concentrations smaller than 3 10^-5M further and irreversibly increase the fraction of the stretched conformers. The activation parameters for this change are compatible with the assessment that no equilibrium is attained between the two families of conformers even after several hours at room temperature, since the barriers arc higher than kT at this temperature. The present results and those previously reported on the excited-state processes of biliverdin dimethyl esters are explained on the basis of a scheme in which the eight possible ring B/C isomers of biliverdin dimethyl ester are interconverted through intra-and intermolecular proton transfers, rotations around C-C single bonds, and E-Z photoisomerizations around C = C double bonds.     

Novel Copolymers of Styrene. 4. Halophenoxy Ring-Substituted 2-Cyano-3-phenyl-2-propenamides

Novel electrophilic trisubstituted ethylenes, halophenoxy ring substituted 2-cyano-3-phenyl-2-propenamides, RC₆H₄CH?C(CN)CONH₂,where R is 4-(4-bromophenoxy), 2-(4-chlorophenoxy), 3-(4-chlorophenoxy), 4-(3-chlorophenoxy), 4-(4-chlorophenoxy), and 4-(4-fluorophenoxy) were prepared and copolymerized with styrene. The monomers were synthesized by potassium hydroxide catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and cyanoacetamide, and characterized by CHN elemental analysis, IR, ¹H- and ¹³C-NMR. Novel copolymers of the ethylenes and styrene were prepared at equimolar monomer feed composition by solution in the presence of a radical initiator, AIBN at 70°C. The compositions of the copolymers were calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H- and ¹³C-NMR, GPC, DSC, and TGA. Thus, the order of relative reactivity (1/r₁) is 4-(4-ClC₆H₄O) (2.01) > 4-(4-FC₆H₄O) (0.89) > 4-(4-BrC₆H₄O) (0.73) > 3-(4-ClC₆H₄O) (0.65) > 2-(4-ClC₆H₄O) (0.24) > 4-(3-ClC₆H₄O) (0.22). High T_g of the copolymers in comparison with that of polystyrene indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200–500°C range with residue (10.4–15.0 wt%), which then decomposed in the 500-800°C range.     

Novel Copolymers of Trisubstituted Ethylenes and Styrene. 8. Fluoro Ring-Substituted Ethyl 2-Cyano-1-oxo-3-phenyl-2-propenylcarbamates

Electrophilic trisubstituted ethylenes, fluoro ring-substituted ethyl 2-cyano-1-oxo-3-phenyl-2-propenylcarbamates, RC₆H₃CH = C(CN)CONHCO₂C₂H₅(where R is 4-F-3-CH₃, 2-CF₃, 4-CF₃, 2,4-diF, 2,5-diF, 2,6-diF, 3,4-diF, and 3,5-diF), were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and N-cyanoacetylurethane, and characterized by CHN analysis, IR, ¹H- and ¹³C-NMR. All the ethylenes were copolymerized with styrene (M₁) in solution with radical initiation (ABCN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, ¹H- and ¹³C-NMR. The order of relative reactivity (1/r ₁) for the monomers 4-CF₃ (5.4) > 2,6-diF (2.0) > 2,4-diF (1.7) > 2,5-diF (1.0) > 2-CF₃ (0.8) > 3,4-diF (0.5) > 3,5-diF (0.4) > 4-F-3-CH₃ (0.3). High T _g of the copolymers in comparison with that of polystyrene indicates decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene structural unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in 270–420°C with residue (5–13% wt), which then decomposed in the 420–650°C range.     

Conformational Analysis of the cis- and trans-Isomers of FK506 by NMR and Molecular Dynamics

The potent immunosuppressant drug FK506 ( 2 ) has been examined by ¹H- and ¹³C-NMR spectroscopy and NOE-restrained molecular dynamics to elucidate the conformation in solution. A combination of two- and three-dimensional NMR techniques was used to completely assign the ¹H- and ¹³C-NMR chemical shifts of the two configurational isomers resulting from the cis-trans isomerization about the single amide bond. Hetero- and homonuclear coupling constants were measured to assign the diastereotopic methylene protons at C(16), C(18), and C(23). Intramolecular H? H distances were defined from NOESY spectra recorded at ?30° in CDCl₃ and used as constraints in molecular-dynamics simulations. The conformational preferences of 2 in solution are discussed in light of the constitutional features recently proposed to be necessary for binding and activity.     

SYNTHESIS AND RADICAL COPOLYMERIZATION OF TRISUBSTITUTED ETHYLENES WITH STYRENE. 6. ALKOXY,PHENOXY, AND CYANO RING-SUBSTITUTED METHYL-2-CYANO-3-PHENYL-2-PROPENOATES

Electrophilic trisubstituted ethylene monomers, ring-substituted methyl 2-cyano-3-phenyl-2-propenoates, RC₆H₄CH?C(CN) CO₂CH₃ (where R is 4-C₂H₅O, 4-C₃H₇O, 4-C₄H₉O, 3-C₆H₅O, and 3-CN), were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and methyl cyanoacetate, and characterized by CHN elemental analysis, IR, ¹H- and ¹³C-NMR. All the propenoates were copolymerized with styrene (M₁) in solution with radical initiation (AIBN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, ¹H- and ¹³C-NMR. The order of relative reactivity (1/r₁ ) for the monomers is 3-CN (1.21) > 3-C₆H₅O (1.16) > 4-C₂H₅O (0.94) > 4-C₃H₇O (0.8305) > 4-C₄H₉O (0.616). The high T _g's of the copolymers (> 130°C) in comparison with that of polystyrene indicate a substantial decrease in the chain mobility of the copolymers due to the high dipolar character of the trisubstituted monomer unit. Gravimetric analysis indicated that the copolymers decompose in the range 300–400°C.