Supporting Information for Boronic Acid–DMAPO Cooperative Catalysis for Dehydrative Condensation Between Carboxylic Acids and Amines

Supporting Information for Boronic Acid–DMAPO Cooperative Catalysis for Dehydrative Condensation Between Carboxylic Acids and Amines

Electronic Supplementary Material (ESI) for Chemical Science. This journal is © The Royal Society of Chemistry 2015 Supporting Information for Boronic Acid–DMAPO Cooperative Catalysis for Dehydrative Condensation between Carboxylic Acids and Amines Kazuaki Ishihara*†‡ and Yanhui Lu† †Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan ‡Japan Science and Technology (JST), CREST, Japan E-mail: [email protected] Contents General Methods……………………………………………………………….….……..……S2 Detailed Synthetic Procedures and Characterization of the Products…………….….…....S2 Inert Species 9…………………..………………………………….………………………....S11 Control Experiments for the Chemoselective Dehydrative Condensation of Unsaturated Carboxylic Acids………………………………………………….…....S15 References…………………………………………………………………………………….S17 1H and 13C NMR Charts of New Compounds……………………………………….……..S18 S1 Experimental section General Methods. IR spectra were recorded on a JASCO FT/IR-460 plus spectrometer. 1H NMR spectra were measured on a JEOL ECS-400 spectrometer (400 MHz) at ambient temperature. Data were recorded as follows: chemical shift in ppm from internal tetramethysilane on the δ scale, multiplicity (s = singlet; d = doublet; t = triplet; m = multiplet), coupling constant (Hz), and integration. 13C NMR spectra were measured on a JEOL ECS-400 (100 MHz). Chemical shifts were recorded in ppm from the solvent resonance employed as the internal standard (CDCl3 at 77.0 11 ppm). B NMR spectra were taken on a JEOL ECS-400 (128 MHz) spectrometer using B(OMe)3 as an external reference. Analytical HPLC was performed on a Shimadzu Model LC-10AD instrument coupled diode array-detector SPD-MA-10A-VP using a column of Daicel CHIRALCEL OD-H (4.6 # 250 mm). Optical rotations were measured on a RUDOLPH AUTOPOL IV digital polarimeter. For TLC analysis, Merck precoated TLC plates (silica gel 60 F254 0.25 mm) were used. For preparative column chromatography, Merck silica gel 60 (0.040–0.063 mm) was used. High resolution mass spectral analysis (HRMS) was performed at Chemical Instrument Facility, Nagoya University. Dry toluene was purchased from Kanto as the “anhydrous” and stored under nitrogen. Fluorobenzene was purchased from TCI and used directly, benzene was purchased from Wako and used directly. Molecular sieves were activated by heating in a flask by a microwave oven for 1 min and then placed under high vacuum for 10 min. 3,4,5-Trifluorophenylboronic acid 1 (Wako), 3,5-bis(trifluoromethyl)phenylboronic acid 2 (Aldrich), phenylboronic acid (Wako), 4-(N,N-dimethylamino)pyridine N-oxide (DMAPO) (TCI) and other materials were obtained from commercial supplies and used without further purification. 2-[(N,N-diisopropylamino)methyl]phenylboronic acid 31 and 2-iodo-5-methoxyphenylboronic acid 4b2 were previously reported. General procedure for the amide condensation under azeotropic reflux conditions: A 10-mL, single-necked, round-bottomed flask equipped with a Teflon-coated magnetic stirring bar and a 5-mL pressure-equalized addition funnel [containing a cotton plug and ca. 2 g of activated molecular sieves 4Å (pellets)] surmounted by a reflux condenser was charged with carboxylic acid, ArB(OH)2, and DMAPO in fluorobenzene or benzene or toluene (0.2 M). Dean-Stark apparatus was also available in place of a pressure-equalized addition funnel containing molecular sieves. After the mixture was stirred at ambient temperature for 5 min, amine (1.0 equiv) was added. The resulting mixture was heated under azeotropic reflux conditions with the removal of water for S2 several hours. After the reaction mixture was cooled to ambient temperature, the solvent was evaporated. The residue was purified by column chromatography on silica gel (eluents: hexane– EtOAc = 4:1) to give the desired amide products. N N+ O- p-Pyrrolidinopyridine N-Oxide (PPYO) (Table 1): PPYO was synthesized from p-pyrrolidinopyridine (PPY) according to the literature method to prepare DMAPO.3 3-Chloroperoxybenzoic acid (m-CPBA, 75%, 805 mg, 3.5 mmol) was added to a solution of PPY (435 mg, 2.94 mmol) in dichloromethane (10 mL) at 0 °C. After the reaction mixture was stirred for 5 h at room temperature, it was passed through a column of anion-exchange resin (DOWEXTM 1x2 100–200 Mesh Anion Exchange Resin; Wako Pure Chemical Industries, Ltd.) with methanol, and the filtrate was concentrated by evaporation of the solvent to afford the crude product. The residue was purified by column chromatography on silica gel (NH) (eluents: hexane–EtOAc = 1:1 to chloroform–methanol = 10:1) to give PPYO as a white solid (190 mg, 39% yield). IR (KBr) –1 1 1627, 1516, 1461, 1208, 1188, 818 cm ; H NMR (CDCl3, 400 MHz) δ 2.08 (dt, 4H, J = 3.7, 6.4 13 Hz), 3.33 (t, 4H, J = 6.4 Hz), 6.35 (d, 2H, J = 6.9 Hz), 7.96 (d, 2H, J = 6.9 Hz); C NMR (CDCl3, 100 MHz) δ 25.4 (2C), 47.6 (2C), 107.7 (2C), 140.0 (2C), 145.7; HRMS (FAB) calcd for C9H13N2O [M+H]+ 165.1028, found 165.1033. O Ph Bn N H Et 4 1 N-Benzyl-2-phenylbutanamide (Tables 1 and 2): white solid; H NMR (CDCl3, 400 MHz) δ 0.89 (t, J = 7.3 Hz, 3H), 1.76–1.88 (m, 1H), 2.17–2.29 (m, 1H), 3.25 (t, J = 7.8 Hz, 1H), 4.34 (dd, J = 5.9, 15.1 Hz, 1H), 4.44 (dd, J = 5.9, 14.6 Hz), 5.74 (brs, 1H), 7.14 (d, J = 6.4 Hz, 2H), 13 7.20–7.37 (m, 8H); C NMR (100 MHz, CDCl3) δ 12.4, 26.4, 43.4, 55.1, 127.2, 127.3, 127.4 (2C), 128.0 (2C), 128.6 (2C), 128.7 (2C), 138.4, 140.1, 173.6. O Bn Ph N 5 1 H N-Benzyl Benzamide (Table 2): white solid; H NMR (CDCl3, 400 MHz) δ 4.65 (d, J 13 = 6.0 Hz, 2H), 6.42 (br, 1H), 7.27–7.54 (m, 8H), 7.79 (d, J = 7.3 Hz, 2H); C NMR (CDCl3, 100 MHz) δ 44.1, 127.1 (2C), 127.5, 127.9 (2C), 128.6 (2C), 128.8 (2C), 131.5, 134.4, 138.4, 167.5. O Ph OBn N H Et N-(Benzyloxy)-2-phenylbutanamide (entry 1, Table 3): white solid; IR (KBr) 3213, –1 1 2958, 1655 cm ; H NMR (DMSO-d6, 400 MHz) δ 0.80 (t, J = 7.3 Hz, 3H), 1.57–1.69 (m,1H), 1.89–2.01 (m, 1H), 3.13 (dd, J = 6.4, 8.7 Hz, 1H), 4.73 (s, 2H), 7.20–7.45 (m, 10H), 11.22 (s, 1H); 13 C NMR (DMSO-d6, 100 MHz) δ 12.1, 25.9, 50.0, 76.7, 126.8, 127.7 (2C), 128.2 (5C), 128.9 (2C), + 135.9, 140.2, 169.7; HRMS (ESI) calcd for C17H20NO2 [M+H] 270.1489, found 270.1490. Note: S3 To a solution of O-benzylhydroxylamine hydrochloride (0.50 mmol) in 2 mL of water was added sodium hydrogen carbonate (0.55 mmol, 1.1 equiv) portionwise. Then 3 mL of dichloromethane was added. The resulting mixture was stirred at room temperature for 15 minutes. Organic phases were collected, and water phase was re-extracted with dichloromethane (3 mL x 2). The combined organic layers were washed with brine (5 mL) and dried over anhydrous MgSO4. Removal of the solvent under reduced pressure to give O-benzylhydroxylamine in quantitative yield. Then it was used as a substrate amine following general procedure. OMe O Ph N H Et N-Benzyl-2-phenylbutanamide (entry 2, Table 3): white solid; IR (KBr) 3282, –1 1 1655, 1604, 1511, 1234 cm ; H NMR (CDCl3, 400 MHz) δ 0.92 (t, J = 7.3 Hz, 3H), 1.80–1.91 (m, 1H), 2.21–2.33 (m, 1H), 3.37 (t, J = 7.3 Hz, 1H), 3.76 (s, 3H), 6.80 (d, J = 6.9 Hz, 2H), 7.04 (br, 13 1H), 7.25-7.36 (m, 7H); C NMR (100 MHz, CDCl3) δ 12.5, 26.6, 55.6, 56.0, 114.1 (2C), 121.8 (2C), 127.5, 128.2 (2C), 129.1 (2C), 131.1, 139.8, 156.5, 171.7; HRMS (ESI) calcd for C17H20NO2 [M+H]+ 270.1489, found 270.1491. O Ph NHBn N-benzyl-2-phenylpropanamide (entries 3 and 4, Table 3):6 White solid; 1H NMR (400 MHz, CDCl3) δ 1.56 (d, J = 7.3 Hz, 3H), 3.56 (q, J = 7.2 Hz, 1H), 4.37 (dd, J = 5.9, 15.1 Hz, 1H), 4.42 (dd, J = 5.9, 15.1 Hz, 1H), 5.63 (br, 1H), 7.14 (d, J = 6.9 Hz, 2H), 7.21–7.38 (m, 8H); 13C NMR (CDCl3, 100 MHz) δ 18.6, 43.6, 47.1, 127.35, 127.38, 127.5 (2C), 127.7 (2C), 128.7 (2C), 129.0 (2C), 138.4, 141.4, 174.2. O Bn N H N-Cyclohexyl-2-methyl-3-phenylpropanamide (entry 5, Table 3): White solid; IR –1 1 (KBr) 3293, 2934, 1638, 1552 cm ; HNMR (CDCl3, 400 MHz) δ 0.74–0.78 (m, 1 H), 0.92–1.14 (m, 2 H), 1.17 (d, J = 6.8 Hz, 3 H), 1.21–1.30 (m, 2 H), 1.50–1.72 (m, 4 H), 1.76–1.87 (m, 1 H), 2.28–2.40 (m, 1 H), 2.65 (dd, J = 5.9, 13.2 Hz, 1 H), 2.92 (dd, J = 8.7, 13.2 Hz, 1 H), 3.60–3.75 (m, 13 1 H), 5.00 (d, J = 7.3 Hz, 1H), 7.12–7.32 (m, 5H); C NMR (CDCl3, 100 MHz) δ 17.9, 24.8, 24.9, 25.6, 33.0, 33.1, 40.7, 44.1, 47.8, 126.3, 128.4 (2C), 129.0 (2C), 140.1, 174.5.

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