Bypassing the lack of reactivity of endo-substituted norbornenes with the catalytic rectification–insertion mechanism

The novel rectification–insertion mechanism for the polymerization of polar norbornenes: making alternating copolymers from a single monomer.

. Zoom of the carbonyl region of the 13 C spectrum PNBE(CO 2 Me) 2 prepared with the endo monomer and superimposed deconvolution by three peaks.

Experimental Section
General considerations: All manipulations that involved air-and/or moisture-sensitive compounds were performed in a nitrogen-filled glove-box. Allylpalladium chloride dimer, palladium dichloride, silver hexafluoroantimonate, norbornene, monomer precursors, NBE(CHO), deuterated solvents for NMR and phenyl silanes were all purchased from Sigma-Aldrich and were stored under nitrogen. Solvents and liquid monomers used for polymerisation were dried over molecular sieves and deoxygenated by bubbling nitrogen.
Instrumentation: 1 H, 13 C, 19 F, COSY, DEPT 145, and HSQC NMR spectra were recorded on Bruker Ultrashield 300 MHz or Varian Inova 600 MHz spectrometers at ambient temperature. 1 H and 13 C NMR chemical shifts were referenced to the solvent signal. The molecular weight distributions of the polymers were determined by gel permeation chromatography (GPC) using a Viscotek instrument equipped with one PL-Gel mixed A LS 20 µm column, one PL-Gel mixed B LS 10 µm column and one polypore 5 µm column, a Wyatt DSP refractometer and a Wyatt Dawn light scattering detector. For the PNBE(CO 2 Me) 2 and PNBE(CO 2 Me) polymers, elution was performed in THF at 40 o C, and all samples were analyzed using a dn/dc of 0.03 and 0.028 respectively. For PNBE(CO 2 H), elution was performed at 40 o C in DMF containing 1g/L of LiCl (dn/dc = 0.04). PNBE(CO 2 H) 2 and PCA were analyzed in an aqueous GPC equipped with two Aquagel PAA-M columns from Poly Analytik, using a Wyatt DSP refractometer and a Wyatt Dawn light scattering detector. Elution was performed at 60 o C (0.5 mL/min) using an aqueous buffer (NaHCO 3 0.05 M, NaNO 3 0.1 M, NEt 3 0.02 M, NaN 3 0.05 wt%). All other polymers were analyzed using the same conditions as PNBE(CO 2 Me) 2 , but using dn/dc = 0.04. Crystallographic analysis was performed at the X-ray crystallography laboratory of the University of Delaware, Dept of Chemistry and Biochemistry, by Prof. G. Yapp and Mr G. Andrade. Differential scanning calorimetry measurements (DSC) of solid polymers were performed on a DSC823e (TOPEM modulation) equipped with an FRS5 sample cell, a sample robot, a Julabo FT400 intracooler and an HRS7 sensor from Mettler Toledo. Samples were heated from 50 o C to 300 o C at a rate of 10 o C/minute and data were analyzed with STAR software. The data associated to the second heated ramp are shown.

NBE(CO 2 H) (75% endo)
The synthesis of NBE(CO 2 H) was adapted from reference 2 . Acrylic acid (83g, 1.15 mol, 1.2eq) and hydroquinone (1.2 g, 10.9mmol, 0,01 eq) were dissolved in 50mL of ethyl acetate. This solution was cooled in an iced bath, and freshly cracked cyclopentadiene (63g, 0.95 mol, 1eq) was added dropwise over 60 minutes. The reaction was stirred under reflux for 12h. Ethyl acetate was then evaporated and the product was distilled under vacuum (to yield a color-free liquid (bp = 150 o C at 5 mmHg). Yield : 100g (76%). The liquid crystallized when left for a few days. 1

NBE(CO 2 Me) 2 (trans):
The synthesis of NBE(CO 2 Me) 2 (fumarate) was adapted from reference 3 . Dimethyl fumarate (50g, 0.34mol, 1eq) and hydroquinone (1.5g, 13.6mmol) were dissolved in 150mL of ethyl acetate. This solution was cooled in an iced bath, and freshly cracked cyclopentadiene (25g, 0.38 mol, 1.11eq) was added dropwise over 60 minutes. The reaction was stirred under reflux for 12h. Ethyl acetate was then evaporated and the product was distilled under vacuum to yield a color-free liquid (bp = 150 o C at 5 mmHg). During distillation, the column was monitored as an impurity (identified as dimethyl fumarate) tended to plug the column. Yield: 42g (0.2mol, 59%). 1

CA (35% endo):
The synthesis of CA (35% endo) was adapted from reference [5]. In a 250ml Schlenk flask equipped with a condenser, CA (100% endo) (50g, 0.30 mol) was heated at 180 o C during 12 hours under a nitrogen flow. The walls of the Schlenk tube were covered with white crystals which were carefully collected, and proved to be CA containing 35% endo isomer and 65% exo isomer, as measured by 1

CA (20% endo):
The synthesis of CA (20% endo) was adapted from reference [5]. In a 250ml Schlenk flask equipped with a condenser, CA (35% endo) (50g, 0.30 mol) was heated at 180 o C during 12 hours under a nitrogen flow. The walls of the Schlenk tube were covered with white crystals which were carefully collected, and proved to be CA containing 20% endo isomer and 80% exo isomer, as measured by 1

NBE(CO 2 Me) 2 (0% endo):
The synthesis of NBE(CO 2 ME) 2 (0 % endo) was adapted from reference 4 . CA (0% endo) (34g, 0.21 mol) and p-TsOH (1g, 5.8 mmol) were dissolved in MeOH (100 mL) in a round bottom flask and heated at reflux for 24 hours. The methanol was evaporated, and the slurry was diluted with ethyl acetate and extracted with water, dried over MgSO 4 , filtered and concentrated on a rotary evaporator. The product was distilled under vacuum to yield a color-free liquid (bp = 150 o C at 5 mmHg). Care was taken to monitor the column and the condenser as the product tended to crystallize and plug the column. Yield 34g (0.16 mol, 76%). The liquid was fully crystallized a few hours after distillation. 1

NBEimide (35% endo):
In a 250ml Schlenk flask equipped with a condenser, CA (35% endo) (30g, 0.183mol, 1eq) was dissolved in 150g of THF. This solution was cooled in an iced bath, and allyl amine (15g, 0.262mol, 1.43eq) was added dropwise over 60 minutes (reaction very exothermic). A white precipitate was immediately formed. When the addition was complete, the reaction was stirred at room temperature for 2 hours. The solution was concentrated on a rotary evaporator to yield an off-white solid. The product was distilled under vacuum to yield a color-free liquid (bp=200 o C at 5 mmHg). The high temperature induces the imidation reaction conducting to formation of water which was trapped in an dry-S10 ice trap connected to the vacuum outlet. Care was taken to monitor the column and the condenser as the product tended to crystallize and plug the column. Occasionally, the column and refrigerant walls were heated to avoid plugging. Yield 31g (0.152mol, 83%). 1

NBEimide (5% endo):
In a 250ml Schlenk flask equipped with a condenser, CA (20% endo) (30g, 0.183 mol, 1eq) was dissolved in 150g of THF. This solution was cooled in an iced bath, and allyl amine (15g, 0.262mol, 1.43eq) was added dropwise over 60 minutes (reaction very exothermic). A white precipitate was immediately formed. When the addition was complete, the reaction was stirred at room temperature for 2 hours. The solution was vacuum-filtered in order to separate the solid from the solution. We believe that the solid is enriched in endo adduct whereas the liquid contains the exo adduct. The solution was cooled in the fridge, leading to the precipitation of endo rich adducts. After separation, the solution was concentrated on a rotary evaporator to yield a white solid. Yield 16g. The product was distilled under vacuum to yield a color-free liquid (bp=200 o C at 5 mmHg). The high temperature induces the imidation reaction conducting to formation of water which was trapped in an dry-ice trap connected to the vacuum outlet. Care was taken to monitor the column and the condenser as the product tended to crystallize and plug the column. To avoid the crystallization on the column walls the column was heated at 60 o C. Yield 15g (0.074 mol, 40%). 1

Compound 2-H 2 O
This compound was prepared in the same manner as 2, but by replacing deuterated tetrachloroethane by a mixture of deuterated nitreomethane:water (9.5:0.5 v:v). Crystals were obtained by slow evaporation of the solvent.

Preparation of Polymers (Typical polymerisation):
With solvent: A stock solution of catalyst 1 was prepared by adding [PdCl(C 3 H 5 )] 2 (100mg, 273 µmol, 546 µmol of Pd, 1 eq) and AgSbF 6 (230mg, 669 µmol, 1.22 eq) to nitromethane (10g, [1]=54.6 µmol/g). Then the solution was filtered using a 0.22µm filter to remove the AgCl precipitate. A transparent yellow catalytic solution was obtained. A vial was loaded with part of the stock solution of 1 (0.875g, 47.78 µmol, 1eq) nitromethane (0.125g) and NBE(CO 2 Me) 2 (1g, 4.761mmol, 100eq). The solution was heated at 70°C under vigorous stirring for 24h. The polymer was precipitated by adding diethyl ether (10ml) and was washed 5 times with diethyl ether. It was then filtered and dried under vacuum at 80°C overnight.        The exothermic transition at 160 o C for PCH 2 OH is not associated with a Tg, as a Tg is expected to be endothermic and the corresponding cooling curve does not show any thermal transition. Putatively, this thermal transition is assigned to an irreversible dehydration reaction. The polymer PNBE(CHO) is not sufficiently stable to be heated up to 300 o C.

Figure S49
ORTEP view of 2-H 2 O with 50% probability ellipsoids Figure S50. ORTEP view of 3-THF with 50% probability ellipsoids (for the sake of clarity, the SbF 6 anion has been omitted) Figure S51. ORTEP view of 2s with 50% probability ellipsoids (for the sake of clarity, the four SbF 6 anions and solvent molecules have been omitted) Figure S52. ORTEP view of 3s with 50% probability ellipsoids (for the sake of clarity, the SbF 6 anion and solvent molecules have been omitted) Figure S53. ORTEP view of 4Ns with 50% probability ellipsoids (for the sake of clarity, the SbF 6 anion and solvent molecules have been omitted)