Supporting Information for: Displacement of Dinitrogen by Oxygen: A Methodology for the Catalytic Conversion of Diazocarbonyl Compounds to Ketocarbonyl Compounds by 2,6-Dichloropyridine-N-oxide Yang Yu, a Qiang Sha, b Hui Cui, a Kory S. Chandler, a Michael P. Doyle a * a Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249 b Department of Chemistry, College of Sciences, Nanjing Agricultural University, Nanjing, China 210095 Corresponding Author * E-mail: michael.doyle@utsa.edu. Content S1 S2 S3 S9 S11 General Information Optimization of Reaction Conditions for the Oxidation of 1a General Procedure for Oxygen Transfer Reaction Applications in C-C Bond Formation Coordination Studies on N-oxides with Rhodium Catalyst by UV-vis Spectroscopy and 1 H NMR S17 S18 References 1 H NMR and 13 C NMR Spectra
General Information All reactions, unless noted, were performed in oven-dried (120 C) glassware with magnetic stirring under an inert atmosphere of dry nitrogen. Analytical thin layer chromatography (TLC) was carried out using EM Science silica gel 60 F254 plates; visualization was accomplished with UV light (254 nm). Liquid chromatography was performed by flash chromatography of the indicated system on silica gel (230-400 mesh). Melting points were obtained uncorrected from an Electro Thermo Mel-Temp DLX 104 device. Column chromatography was performed on a CombiFlash Rf 200 purification system using normal phase disposable columns. Coordination experiments were performed on a Cary 5000 UV-Vis spectrometer. Proton nuclear magnetic resonance ( 1 H NMR) spectra were recorded in CDCl 3 on an Agilent DD2-500 spectrometer (500 MHz) and Bruker Avance III HD 300 MHz spectrometer. Chemical shifts were reported as δ in ppm downfield from internal Me 4 Si. The peak information was described as: br = broad, s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet, comp = composite; coupling constant(s) in Hz. The number of protons (n) for a given resonance was indicated by nh. Coupling constants were reported as J-values in Hz. Carbon nuclear magnetic resonance ( 13 C NMR) spectra were recorded in CDCl 3 on an Agilent DD2-500 spectrometer (126 MHz) with complete proton decoupling, Bruker Avance III HD 300 MHz spectrometer and a Bruker Avance III HD 500 MHz spectrometer. Enantiomeric excesses were determined by high-performance liquid chromatography (HPLC) using an Agilent 1260 Infinity HPLC system with a Daicel Chiralpak AD-H column. High-resolution mass spectra (HRMS) were performed on a TOF-CS mass spectrometer using CsI as the standard. Metal catalysts were purchased from Aldrich or Strem and used without further purification. Solvents were dried according to standard procedures. 1 Other chemicals were obtained from commercial sources and used as received. S1
Optimization of Reaction Conditions for the Oxidation of 1a. a entry O-transfer reagent Catalyst temperature time yield (%) b 1 C 5 H 5 N-O Rh 2 (OAc) 4 23/82 C 24 h trace 2 4-ClC 5 H 5 N-O Rh 2 (OAc) 4 23 C 24 h 0 3 4-MeC 5 H 5 N-O Rh 2 (OAc) 4 23 C 24 h 0 4 4-NO 2 C 5 H 5 N-O Rh 2 (OAc) 4 23 C 24 h 0 5 4-MeOC 5 H 5 N-O Rh 2 (OAc) 4 23 C 24 h 0 6 3,5-Br 2 C 5 H 5 N-O(2a) Rh 2 (OAc) 4 23 C 24 h 0 7 2,6-Cl 2 C 5 H 5 N-O (2b) Rh 2 (OAc) 4 23 C 1 h 90 8 2,6-Cl 2-4-NO 2 C 5 H 5 N-O Rh 2 (OAc) 4 23 C 1.5 h 82 (2c) 9 2,6-Me 2 C 5 H 5 N-O(2d) Rh 2 (OAc) 4 23 C 24 h 30 10 2,6-Br 2 C 5 H 5 N-O (2e) Rh 2 (OAc) 4 23 C 1.5 h 69 11 c 2,6-Cl 2 C 5 H 5 N-O (2b) Rh 2 (oct) 4 23 C 0.67 h 94 12 d 2,6-Cl 2 C 5 H 5 N-O (2b) None 23/82 C 12 h 0 13 e none Rh 2 (OAc) 4 23 C 24 h complex 14 f DMSO Rh 2 (OAc) 4 23/75 C 24 h 0 15 g DMSO none 75 C 24 h 0 S2
a. Standard reaction conditions: Rh 2 (OAc) 4 (2.0x10-3 mmol) was added to a 1.0 ml DCM solution of 1a (0.20 mmol) and pyridine N-oxides 2 (1.0 equiv) at room temperature. b. NMR yield with 1,3,5-trimethoxylbenzene as internal standard. c. 4 Å Molecular sieves (50 mg) were added into a solution of 1a (28.4 mg, 0.20 mmol), 2,6-dichloropyridine-N-oxide 2b (32.8 mg, 0.20 mmol, 1.0 equiv) in DCM (1.0 ml). The mixture was stirred for 10 min before the addition of Rh 2 (oct) 4 (1.56 mg, 2.0x10-3 mmol) at room temperature. Reaction time is 40 min. d. No rhodium catalyst was added. There was no reaction after 12 h, only starting material was recovered. e. No O-transfer reagent was added. The starting material was decomposed, however the reaction materials became very complex after stirring for 24 h. f. 3 Equiv of anhydrous DMSO was used as oxygen transfer reagent with DCE as the solvent at 23 or 75 C. g. no rhodium catalyst, anhydrous DMSO was used as solvent (0.2 M) at 75 C. General Procedure for Oxygen Transfer Reaction of Acceptor-Acceptor Diazo Compounds 1a-f and Analytical Data for the Hydrate Products 4 Å Molecular sieves (50 mg) were added to a solution of 1a-f (0.2 mmol), 2,6-dichloropyridine-N-oxide (32.8 mg, 0.20 mmol, 1.0 equiv) in DCM (1 ml). The mixture was stirred for 10 min before addition of Rh 2 (OAc) 4 (0.884 mg, 2.00 10-3 mmol) or Rh 2 (oct) 4 (1.56 mg, 2.00 10-3 mmol) at room temperature. Reactions were monitored by TLC. After the reactions were complete, molecular sieves were removed by the filtration with cotton. The filtrate was concentrated to afford the crude reaction S3
mixture. The yields for 3a-f were determined by 1 H NMR from the crude reaction mixture with 1,3,5-trimethoxylbenzene as the internal standard in molecular sieves dried CDCl 3 (0.5 ml). Since the tricarbonyl compounds 3a-f are sensitive to water, the hydrate products 5a-f were obtained after column chromatography on silica gel. The hydrate products 5a-f were purified by flash column chromatography (SiO 2, ethyl acetate/hexane). Characterization data of compounds 5a, 1 5b, 2 5d, 3 5f 4 were previously reported in the literature. Analytical data for 5c, 5e are listed below. Methyl 2,2-Dihydroxy-3-oxobutanoate (5a) White solid, 21.3 mg, 72% yield. Methyl 2,2-Dihydroxy-3-oxopentanoate (5b) Yellow solid, 25.3 mg, 78% yield. Dimethyl 2,2-Dihydroxymalonate (5c) White solid (mp = 79-80 C), 79% yield. 1 H NMR (500 MHz, CDCl 3 ) δ 4.92 (br s, 2H), 3.89 (s, 6H); 13 C NMR (126 MHz, CDCl 3 ) δ 168.7, 90.2, 54.0. HRMS (ESI) calculated for C 5 H 8 O 6 Na [M+Na] + : 187.0213; found: 187.0208. 2,2-Dihydroxycyclohexane-1,3-dione (5d) White solid, 23.6 mg, 82% yield. 2,2,2-Trichloroethyl 2,2-Dihydroxy-3-oxobutanoate (5e) White solid (mp = 84-85 C), 80% yield. 1 H NMR (300 MHz, CDCl 3 ) δ 4.93 (br s, 2H), 4.88 (s, 2H), 2.39 (s, 3H); 13 C NMR (126 MHz, CDCl 3 ) δ 199.7, 167.3, 93.7, 92.5, 75.0, 23.3. HRMS (ESI) calculated for S4
C 6 H 7 Cl 4 O 5 [M+Cl] - : 298.9053; found: 298.9052. Methyl 2,2-Dihydroxy-3-oxo-3-phenylpropanoate (5f) White solid, 35.7 mg, 85% yield. Benzyl 2,2-Dihydroxy-3-oxobutanoate (5g) White solid, 35.0 mg, 78% yield. Ethyl 2,2-Dihydroxy-3-oxo-3-phenylpropanoate (5h) White solid, 31.4 mg, 70% yield. General Procedure for Oxygen Transfer Reaction of Donor-Acceptor Diazo Compounds 6a-d and Analytical Data for the product 7a-d 4 Å Molecular sieves (50 mg) were added to a solution of 6a-d (0.200 mmol), 2,6-dichloropyridine-N-oxide (32.8 mg, 0.200 mmol, 1.0 equiv) in DCM (1.0 ml). The mixture was stirred for 10 min before addition of Rh 2 (oct) 4 (1.56 mg, 2.00 10-3 mmol) at room temperature. The reactions were monitored by TLC. The products 7a-d were purified by flash column chromatography (SiO 2, ethyl acetate/hexane). Characterization data of compounds 7a, 5 7b, 6 7c, 7 7d 8 were previously reported in the literature. 1-Phenylpropane-1,2-dione (7a) S5
colorless oil. 27.3 mg, 92% yield. Ethyl 2-Oxo-2-phenylacetate (7b) colorless oil. 32.1 mg, 90% yield. Methyl 2-(2-Bromophenyl)-2-oxoacetate (7c) light yellow oil. 44.7 mg, 92% yield. Methyl 2-(4-Methoxyphenyl)-2-oxoacetate (7d) white solid. 35.3 mg, 91% yield. Competition reactions for substrates 1g, 1h and 1i. 4 Å Molecular sieves (50 mg) were added to a solution of 1g (43.6 mg, 0.20 mmol), 2,6-dichloropyridine-N-oxide (32.8 mg, 0.20 mmol, 1.0 equiv; and 164.0 mg, 1.0 mmol, 5.0 equiv) in DCM (1.0 ml). The mixture was stirred for 10 min before addition of Rh 2 (oct) 4 (1.56 mg, 2.00 10-3 mmol) at room temperature. The reactions were monitored by TLC. After the reaction was complete, molecular sieves were removed by the filtration with cotton. The filtrate were concentrated to afford the S6
crude reaction mixture. The yields for 3g (64%) and 10 (25%) were determined by 1 H NMR of crude reaction mixture with 1,3,5-trimethoxylbenzene as the internal standard in molecular sieves dried CDCl 3 (0.5 ml). Only 3g (85% yield) was obtained when 5 equiv of 2,6-dichloropyridine-N-oxide was used. Since the tricarbonyl compound 3g are sensitive to water, the hydrate product 5g was obtained after column chromatography on silica gel. Compounds 5g and 10 were purified by flash column chromatography (SiO 2, ethyl acetate/hexane). Characterization data of compound 5g 1 were previously reported in the literature. 4 Å Molecular sieves (50 mg) were added to a solution of 1i (34.0 mg, 0.20 mmol), 2,6-dichloropyridine-N-oxide (32.8 mg, 0.20 mmol, 1.0 equiv; and 164.0 mg, 1.0 mmol, 5.0 equiv) in DCM (1.0 ml). The mixture was stirred for 10 min before addition of Rh 2 (oct) 4 (1.56 mg, 2.00 10-3 mmol) at room temperature. The reactions were monitored by TLC. The yields for 3i (10%) and 9 (51%) were determined by 1 H NMR with 1,3,5-trimethoxylbenzene as the internal standard in molecular sieves dried CDCl 3 (0.5 ml). 3i (49% yield) and 9 (37% yield) were obtained when 5 equiv of 2,6-dichloropyridine-N-oxide was used. Since the tricarbonyl compound 3i are sensitive to water, the hydrate product 5i was obtained after column chromatography on silica gel. 5i and 9 were purified by flash column chromatography (SiO 2, ethyl acetate/hexane). Characterization data of compounds 5i, 1 9 9 were previously reported in the literature. S7
4 Å Molecular sieves (50 mg) were added to a solution of 1h (43.6 mg, 0.20 mmol), 2,6-dichloropyridine-N-oxide (32.8 mg, 0.20 mmol, 1.0 equiv; 98.4 mg, 0.60 mmol, 3.0 equiv; 164.0 mg, 1.0 mmol, 5 equiv; 328.0 mg, 2.0 mmol, 10.0 equiv) in DCM (1.0 ml). The mixture was stirred for 10 min before addition of Rh 2 (oct) 4 (1.56 mg, 2.00 10-3 mmol) at room temperature. The reactions were monitored by TLC. The yields for 3h (60%), 8 (28%) were determined by 1 H NMR with 1,3,5-trimethoxylbenzene as the internal standard in molecular sieves dried CDCl 3 (0.5 ml). 3h (66% yield) and 8 (24% yield) were obtained when 3 equiv of 2,6-dichloropyridine-N-oxide was used. 3h (67% yield) and 8 (15% yield) were obtained when 5 equiv of 2,6-dichloropyridine-N-oxide was used. 3h (77% yield) and 8 (12% yield) were obtained when 10 equiv of 2,6-dichloropyridine-N-oxide was used. Since the tricarbonyl compound 3h are sensitive to water, the hydrate product 5h was obtained after column chromatography on silica gel. Compounds 5h, 8 were purified by flash column chromatography (SiO 2, ethyl acetate/hexane). Characterization data of compounds 5h, 1 8 10 were previously reported in literature. Applications in C-C Bond Formation Reactions General Procedure for One-pot Oxygen Transfer Reaction Cascade S8
Carbonyl-ene Reaction. 4 Å Molecular sieves (100 mg) were added to a solution of 1a (56.8 mg, 0.400 mmol), 2,6-dichloropyridine-N-oxide (65.6 mg, 0.400 mmol, 1.0 equiv) in DCM (2.0 ml). The mixture was stirred for 10 min before addition of Rh 2 (oct) 4 (3.12 mg, 4.00 10-3 mmol) at room temperature. The reaction monitored by TLC was complete in one hour after which the reaction solution was cooled to -78 C. Anhydrous Sc(OTf) 3 (19.6 mg, 4.00 10-2 mmol) was added under nitrogen followed by α-methylstyrene (141.8 mg, 1.20 mmol, dropwise at -78 C). After stirring for 10 min, the solution was warmed to 0 C and stirred for additional 50 min. The reaction was directly subjected to flash column chromatography (SiO 2, hexane and EtOAc) to afford 11a (76.4 mg, 77% yield for 2 steps) as a colorless oil. The characterization of 11a were reported in the literature. 1 General Procedure for One-pot Oxygen Transfer Reaction Cascade Asymmetric Aldol Reaction. 4 Å Molecular sieves (100 mg) were added to a solution of 1a (56.8 mg, 0.400 mmol), 2,6-dichloropyridine-N-oxide (65.6 mg, 0.400 mmol, 1.0 equiv) in DCM (2.0 ml). S9
The mixture was stirred for 10 min before addition of Rh 2 (oct) 4 (3.12 mg, 4.00 10-3 mmol) at room temperature. The reaction was complete in one hour monitored by TLC after which cyclohexone (78.5 mg, 0.800 mmol) and L-proline (9.21 mg, 8.00 10-2 mmol) were added in sequence. Then the reaction mixture was stirred at room temperature for 24 h. After reaction was complete, the product mixture was concentrated and purified by flash column chromatography (SiO 2, hexane and EtOAc) to afford 12 (63.91 mg, 70% yield) as cis-12 (93% ee) and trans-12 (93% ee) isomers (cis: trans = 53:47). The characterization of cis and trans isomers of 12 and their HPLC conditions to determine ee value were reported in the literature. 2 Larger scale of oxygen transfer reaction for 1a and subsequent carbonyl-ene reaction: 4 Å Molecular sieves (250 mg) were added to a solution of 1a (142.0 mg, 1.0 mmol), 2,6-dichloropyridine-N-oxide (164.0 mg, 1.0 mmol, 1.0 equiv) in DCM (5 ml). The mixture was stirred for 10 min before addition of Rh 2 (oct) 4 (7.81 mg, 1.00 10-2 mmol) at room temperature. Reaction was monitored by TLC. After the reaction was complete, molecular sieves were removed by the filtration with cotton. The filtrate was concentrated to afford the crude reaction mixture. The yield for 3a was determined by 1 H NMR from the crude reaction mixture with 1,3,5-trimethoxylbenzene as the internal standard in molecular sieves dried CDCl 3 (0.5 ml), which is 90% yield (3a:5a = 95:5). S10
4 Å Molecular sieves (250 mg) were added to a solution of 1a (142.0 mg, 1.0 mmol), 2,6-dichloropyridine-N-oxide (164.0 mg, 1.0 mmol, 1.0 equiv) in DCM (5.0 ml). The mixture was stirred for 10 min before addition of Rh 2 (oct) 4 (7.81 mg, 1.00 10-2 mmol) at room temperature. The reaction monitored by TLC was complete in one hour after which the reaction solution was cooled to -78 C. Anhydrous Sc(OTf) 3 (49.2 mg, 1.00 10-1 mmol) was added under nitrogen followed by α-methylstyrene (354.5 mg, 3.0 mmol, dropwise at -78 C). After stirring for 10 min, the solution was warmed to 0 C and stirred for additional 50 min. The reaction was directly subjected to flash column chromatography (SiO 2, hexane and EtOAc) to afford 11a (183.7 mg, 74% yield for 2 steps) as a colorless oil. Coordination Studies on N-Oxides with Rhodium Catalyst by UV-Vis Spectroscopy and 1 H NMR UV/Vis spectra for the coordination between 2,6-dichloropyridine-N-oxide (2b) and Rh 2 (oct) 4 were acquired by the sequential additions of 2,6-dichloropyridine-N-oxide (0.30 M in DCM, from 0.20 equiv to 2.0 equiv) to Rh 2 (oct) 4 (1.20 10-2 M) in 2.5 ml of anhydrous DCM at 23 C. S11
1/ A Abs 2 1 0 0.0024 M 0.0048 M 0.0072 M 0.0096 M 0.0120 M 0.0144 M 0.0168 M 0.0192 M 0.0216 M 0.024 M 0 400 500 600 700 800 Wavelength Equilibrium constants K were determined from a plot of 1/ΔA versus 1/ [2b], which yielded a straight line (r>0.99) with intercept/slope equal to K. The equilibrium constant K = 30.2±1.5 in DCM at 23 C for 2b and Rh 2 (oct) 4 was determined from three different wavelengths (380 nm, 385 nm and 390 nm). 380 nm 10 8 6 4 2 0 y = 0.0179x + 0.568 R² = 0.9998 0 100 200 300 400 500 1/c, L/mol S12
1/ A 1/ A 385 nm 12 10 8 6 4 2 0 y = 0.0223x + 0.6676 R² = 0.9998 0 100 200 300 400 500 1/c, L/mol 390 nm 14 12 10 8 6 4 2 0 y = 0.0281x + 0.8143 R² = 0.9997 0 100 200 300 400 500 1/c, L/mol The 1 H NMR spectrum shows no obvious chemical shift. S13
Abs UV/Vis spectra for the coordination between pyridine-n-oxide and Rh 2 (oct) 4 were acquired by the sequential additions of pyridine-n-oxide (0.30 M in DCM, from 0.20 equiv to 2.0 equiv) to Rh 2 (oct) 4 (6.0 10-3 M) in 2.5 ml of anhydrous DCM at 23 C. 4 3 2 0 0.0024 M 0.0048 M 0.0072 M 0.0096 M 0.0120 M 0.0144 M 0.0168 M 0.0192 M 0.0216 M 0.024 M 1 0 400 500 600 700 800 Wavelength S14
1/ A 1/ A Equilibrium constants K were determined from a plot of 1/ Δ A versus 1/ [pyridine-n-oxide], which yielded a straight line (r>0.99) with intercept/slope equal to K. The equilibrium constant K = 43.2±3.1 in DCM at 23 C for 2b and Rh 2 (oct) 4 was determined from three different wavelengths (400 nm, 405 nm and 410 nm). 400 nm 7 6 5 4 3 2 1 0 y = 0.0067x + 0.3101 R² = 0.9975 0 200 400 600 800 1000 1/c, L/mol 405 nm 9 8 7 6 5 4 3 2 1 0 y = 0.0098x + 0.4084 R² = 0.998 0 200 400 600 800 1000 1/c, L/mol S15
1/ A 14 12 10 8 6 4 2 0 410 nm y = 0.0142x + 0.5895 R² = 0.9974 0 200 400 600 800 1000 1/c, L/mol The 1 H NMR spectrum shows a large chemical shift for protons adjacent to the nitrogen atom of pyridine-n-oxide. There is no obvious coordination between 2,6-dichloropyridine and Rh 2 (oct) 4, shown S16
as UV-Vis spectra below. References: 1 Truong, P. M.; Zavalij, P. Y.; Doyle, M. P. Angew. Chem. Int. Ed. 2014, 53, 6468. 2 Sha, Q.; Arman, H.; Doyle, M. P. Chem. Commun. 2016, 52, 108. 3 Seitz, T.; Harms, K.; Koert, U. Synthesis, 2014, 46, 381. 4 Cui, J.; Duan, Y.; Yu, J.; Zhang, C. Org. Chem. Front. 2016, 3, 1686. 5 Andia, A. A.; Miner, M. R.; Woerpel, K. A. Org. Lett. 2015, 17, 2704. 6 Stergiou, A.; Bariotaki, A.; Kalaitzakis, D.; Smonou, I. J. Org. Chem. 2013, 78, 7268. 7 Wang, S. R.; Radosevich, A. T. Org. Lett. 2015, 17, 3810. 8 Fabbri, C.; Bietti, M.; Lanzalunga, O. J. Org. Chem. 2005, 70, 2720. 9 Lee, E.; Kim, E. K.; Jung, K. W.; Lee, K. H.; Kim, Y. S.; Lee, K. H. Bull. Korean Chem. Soc. 1991, 12, 361. 10 Chen, Z. S.; Huang, X. Y.; Gao, J. M.; Ji, K. Org. Lett. 2016, 18, 5876. S17
S18
1 H NMR and 13 C NMR spectra S19
S20
S21
S22
S23
S24
S25
S26
S27
S28
S29
S30
S31
S32
S33
S34
cis-12: S35
trans-12: S36
HPLC spectra for cis-12: rac-cis-12 Chiral cis-12 S37
rac-trans-12 Chiral trans-12 S38