1,3-BIS(2,4,6-TRIMETHYLPHENYL)-IMIDAZOLIDINIUM-CHLORIDE

beige to pink-brown powder

To a solution of diimine (8.0 g, 27.3 mmol) in THF (100 mL) was added NaBHA mixture of 1.12 g (3.03 mmol) of N, N'-bis-(2, 4, 6-trimethylphenylamino)ethane dihydrochloride, 10mL of triethyl orthoformate, and one drop of 96percent formic acid was heated in a distillation apparatus until the ethanol distillation ceased. The temperature of the reaction mixture reached 130 In a flask, the imine(1.3 g, 4.45 mmol) was suspended in ethyl alcohol(65 ml), then cooled to 0 °C and sodium borohydride(3.36 g, 89 mmol) was added slowly, after stirring for 30 min, the mixture was reflux until the reaction solution was changed to colorless, the reaction was complete. The solution was cooled to room temperature, then aqueous saturated sodium chloride(12 ml) was added to stir for 30 min, after that, 50 ml water and 40 ml chloroform was added, organic phase was separated, washed with small amount of water, dried under anhydrous sodium sulfate, and then volatiles were removed under vacuum, yielding lightyellow oil. The oil was purged to next step, in the same flask, ammonium chlorite(261.9 mg, 4.9 mmol), and triethyl orthoformate(4 ml) was added, the mixture was stirred under N2 at 110 °C overnight, then ethyl ether was added to separated yellow solid, filtered and then crystaled through dichloromethane and ethyl ether, affording 1.3 g yellow SIMes*HCl in 85percent yield. 1H NMR(CDCl3, 400 MHz): δ 2.30(s, 6H), 2.40(s, 12H), 4.61(s, 4H), 6.97(s, 4H), 7.27(s, 2H), 9.16(s, 1H); 13C NMR(CDCl3, 100 MHz): δ 17.9, 21.0, 51.9, 129.9, 130.3, 135.0, 140.3, 160.1.In a flask, the imine (1.3 g, 4.45 mmol) was suspended in ethyl alcohol (65 ml), then cooled to 0 °C and sodium borohydride (3.36 g, 89 mmol) was added slowly, after stirring for 30 min, the mixture was heated to reflux until the color of the solution turn into colorless. Cool to room temperature, then aqueous saturated sodium chloride (12 ml) was added to stir for 30 min, after that, 50 ml water and 40 ml chloroform was added, then organic phase was separated, washed with small amount of water, dried under anhydrous sodium sulfate, and then volatiles were removed under vacuum, yielding light yellow oil. The oil was purged to next step. In the same flask, ammonium chlorite (261.9 mg, 4.9 mmol) and triethyl orthoformate (4 ml) was added, the mixture was stirred under NAccording to method Al, diisopropylethylamine (0.34 mL, 1.96 mmol) was added to a stirred solution of A^/V'-dimesitylformamidine (0.5 g, 1.78 mmo.) and dichloroethane (1.36 mL, 17.8 mmol) in a schienk tube. The tube was evacuated until solvent began to bubble and then sealed and heated to 120 According to method Cl, dichloroethane (2.23 mL) was added to a schlenk flask charged with 2, 4, 6-trmethylaniIine (1.64 mL, 11.66 mmo.) and triethyl orthoformate (0.97 mL, 5.83 mmol). The tube was evacuated until solvent began to bubble and then sealed and heated with stirring to 120 According to method Bl, dichloroethane (1.36 ml_) was added to a schlenk flask charged with /VA mixtureof 2, 4, 6-trimethylaniline (11.9 g, 0.088 mol), triethyl orthoformate (7.1 g, 0.048 mol)and acetic acid (0.12 mL) was heated at reflux (?120 ) for 5 h. The mixture wasevaporated until dry under reduced pressure. A mixture of dichloroethane (25 mL)and diisopropylethylamine (8.9 mL, 0.05 mol) was added to the precipitate and afterthat the suspension was stirred at 120 for 5 h in a hermetically sealed Schlenkflask. The formed solution was evaporated to dryness under reduced pressure. Theobtained precipitate was washed with acetone (85 mL) and dried under vacuum at rt.The residue was dissolved in chloroform (300 mL) at 0 C, and then granulatedNaOH (68.0 g, 1.70 mol, with a pellet diameter of '0.5 mm) was added in one portionto the solution at the same temperature under vigorous stirring. Stirring wascontinued until the temperature reaches 18 C (?40 min), then the reaction wasstirred at this temperature for another 4 h (until the end of the heat release process).The precipitate (NaOH) was filtered off, washed with chloroform (2 × 40 mL) andhexane (2 × 40 mL). After the last operation, sodium hydroxide can be used onemore time in the same step. The filtrate was evaporated under reduced pressure.The solid residue was treated with hexane (70 mL) under ultrasonic irradiation for 10min and then held at 4 C for 24 h. The precipitate was filtered off, suspended withmethanol (60 mL), treated by ultrasonic irradiation for 2 min and filtered off. The lastoperation was repeated three more times, after that the white powder was driedunder vacuum at rt to give 14.3 g of the title compound 9 (87% relative to the starting2, 4, 6-trimethylaniline) with >95% purity (by 1H NMR).

N-Heterocyclic Carbene LigandsPrecursor to an N-heterocyclic carbene catalysts