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An All-Purpose Preparation of Oxime Carbonates and Resultant Insights Into the Chemistry of Alkoxycarbonyloxyl Radicals

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An All-Purpose Preparation of Oxime Carbonates and Resultant Insights Into the Chemistry of Alkoxycarbonyloxyl Radicals Electronic Supplementary Material (ESI) for Chemical Science This journal is © The Royal Society of Chemistry 2012 Electronic Supplementary Information An all-purpose preparation of oxime carbonates and resultant insights into the chemistry of alkoxycarbonyloxyl radicals. Roy T. McBurney,* Andrew D. Harper, Alexandra M. Z. Slawin and John C. Walton.* School of Chemistry, University of St. Andrews, EaStChem, St. Andrews, Fife, KY16 9ST, UK. S1 Electronic Supplementary Material (ESI) for Chemical Science This journal is © The Royal Society of Chemistry 2012 Table of Contents General Experimental Section S3 Scheme S1. General one-pot procedure for the synthesis of oxime carbonates. S4 Scheme S2. General two-pot procedure for the synthesis of oxime carbonates. S4 Scheme S3. Chloroformate synthesis of oxime carbonates. S5 Synthesis and Experimental Section S6 Figure S1. The X-ray crystal structure of 5e. S18 Table S1. Crystal data and structure refinement for 5e. S18 Figure S2. The X-ray crystal structure of 9a. S19 Table S2. Crystal data and structure refinement for 9a. S19 UV Photolyses of Oxime Carbonates S20 EPR Spectroscopy S25 EPR spectra S26 Computational Methods S31 DFT Optimised Structures and Energies S31 References S40 1H and 13C NMR spectra of novel compounds S42 S2 Electronic Supplementary Material (ESI) for Chemical Science This journal is © The Royal Society of Chemistry 2012 General Experimental Section All reagents and solvents were purchased from either Sigma Aldrich or Alfa Aesar and used without further purification. Toluene and tetrahydrofuran were distilled over sodium and dichloromethane was distilled over calcium hydride. Benzaldehyde oxime, acetophenone oxime, 4- methoxyacetophenone oxime, and benzophenone oxime were prepared according to the literature procedure,1 as was 4-(1H-indol-3-yl)butan-2-one.2 1-Phenylpent-4-en-1-ol was prepared in an analogous fashion to the method reported by Studer;3 1H NMR and 13C NMR spectra were consistent with literature values.4 Column chromatography was carried out using Silica 60A (particle size 40-63 µm, Silicycle, Canada) as the stationary phase, and TLC was performed on precoated silica gel plates (0.20 mm thick, Sil G UV254, Macherey-Nagel, Germany) and observed under UV light. 1H and 13C NMR spectra were recorded on Bruker AV III 500, Bruker AV II 400 and Bruker AV 300 instruments. Chemical shifts are reported in parts per million (ppm) from low to high frequency and referenced to the residual solvent resonance. Coupling constants (J) are reported in hertz (Hz). Standard abbreviations indicating multiplicity were used as follows: s = singlet, d = doublet, t = triplet, dd = double doublet, q = quartet, m = multiplet, b = broad. Melting points (M.p.) were determined using a Sanyo Gallenkamp apparatus and are reported uncorrected. Mass spectrometry was carried out at the EPSRC National Mass Spectrometry Service Centre, Swansea, UK. One-Pot CDI Oxime Carbonate General Procedure5 1,1-Carbonyldiimidazole (CDI) (1.0 equiv) was dissolved in THF (20 cm3) at 0 °C, alcohol (1 equiv.) in THF (10 cm3) was added dropwise and the solution stirred at 0 °C for 1 h then allowed to warm to rt for another hour. In a second flask oxime (1 equiv.) was dissolved in THF (20 cm3) at 0 °C and sodium hydride was added (0.3 equiv.), the suspension was stirred for 5 min. The imidazole intermediate mixture was then added slowly to the oxime/sodium hydride flask and stirred at 0 °C S3 Electronic Supplementary Material (ESI) for Chemical Science This journal is © The Royal Society of Chemistry 2012 for 30 min before being allowed to warm to rt for a further 2 h. The solvent was removed under reduced pressure and the crude residue was redissolved in EtOAc (100 cm3) and washed with 3 NH4Cl (3 × 100 cm ), dried over MgSO4, filtered and purified by column chromatography (CH2Cl2/Pet Ether 40:60 (1:1) as eluent). Scheme S1. General one-pot procedure for the synthesis of oxime carbonates. Reagents and conditions: i) R1OH, CDI, THF, O °C to rt, 2 h; oxime, NaH, THF, O °C to rt, 2 h. Two-Pot CDI Oxime Carbonate General Procedure6 To a 0 °C solution of 1,1-carbonyldimiidazole (3 equiv.) in THF (30 cm3) was added alcohol (1 equiv.). The reaction was stirred and allowed to warm to rt over 2 h. The solvent was removed under reduced pressure and the crude residue was re-dissolved in EtOAc (100 cm3) and washed 3 with NH4Cl (3 × 100 cm ), dried over MgSO4, filtered and concentrated under reduced pressure. To a solution of oxime (1.5 equiv.) in THF (20 cm3) at 0 °C, pre-treated with sodium hydride (0.3 equiv.), was added a THF solution (10 cm3) of the imidiazole intermediate. The reaction mixture was stirred at 0 °C for 30 min and allowed to warm to rt and stirred for 18 h. The solvent was removed under reduced pressure and the crude residue was re-dissolved in EtOAc (100 cm3) and 3 washed with NH4Cl (3 × 100 cm ), dried over MgSO4, filtered and purified by column chromatography (CH2Cl2/Pet Ether 40:60 (1:1) as eluent). (For the cases where the imidazole carboxylate intermediate was characterised, its spectral data immediately follows the characterisation data for the resultant oxime carbonate.) S4 Electronic Supplementary Material (ESI) for Chemical Science This journal is © The Royal Society of Chemistry 2012 Scheme S2. General two-pot procedure for the synthesis of oxime carbonates. Reagents and conditions: i) R1OH, CDI, THF, O °C to rt, 2 h; ii) oxime, NaH, THF, O °C to rt, 18 h. Chloroformate Synthesis of Oxime Carbonates General Procedure 3 To a stirred 0 °C solution of oxime (1.0 equiv.) and pyridine (1.0 equiv.) in CH2Cl2 (25 cm ) was added dropwise chloroformate (1.0 equiv.). The solution was allowed to warm to rt over 18 h. The 3 3 reaction mixture was diluted with CH2Cl2 (75 cm ) and washed with 1 M HCl (100 cm ), sat. aq. 3 3 NHCO3 (100 cm ) and brine (100 cm ). The organic layer was dried over MgSO4, filtered, concentrated under reduced pressure and purified by column chromatography (gradient elution Pet Ether 40:60 to CH2Cl2). Scheme S3. Chloroformate synthesis of oxime carbonates. Reagents and conditions: i) R1OC(O)Cl, oxime, pyridine, CH2Cl2, O °C to rt, 18 h. S5 Electronic Supplementary Material (ESI) for Chemical Science This journal is © The Royal Society of Chemistry 2012 Synthesis and Experimental Section Benzaldehyde O-phenoxycarbonyl oxime Prepared from phenyl chloroformate (0.68 cm3, 5.42 mmol), benzaldehyde oxime (0.547 g, 4.52 mmol) and pyridine (0.44 cm3, 5.42 mmol) to give a colourless oil (0.255 g, yield = 22%). 1H NMR (300 MHz, CDCl3, 299 K): = 7.26‒7.31 (m, 3H, HAr), 7.39‒7.54 (m, 5H, HAr), 7.77 (dd, J = 1.6 13 Hz, 7.9 Hz, 2H, Ha), 8.45 (s, 1H, Hb); C NMR (75 MHz, CDCl3, 297 K): = 121.0, 126.3, 128.5, 129.0, 129.6, 129.6, 132.0, 150.9, 152.1, 156.5; LR-ESIMS: m/z = 242 [MH]+; HR-ESIMS: m/z = 242.0813 (calcd. for C14H12NO3, 242.0812). Benzaldehyde O-((benzyloxy)carbonyl) oxime - 5a Prepared from benzyl chloroformate (0.63 cm3, 4.42 mmol), benzaldehyde oxime (0.446 g, 3.69 mmol) and pyridine (0.35 cm3, 4.42 mmol) to give a colourless crystalline powder, 0.648 g, yield = 1 69%. M.p. = 58‒61 °C; H NMR (400 MHz, CDCl3, 297 K): = 5.31 (s, 2H, Ha), 7.34‒7.50 (m, 13 8H, HAr), 7.72 (d, J = 9.6 Hz, 2H, Hc), 8.34 (s, 1H, Hb); C NMR (75 MHz, CDCl3, 297 K): = 70.7, 128.8, 129.1 (× 2), 129.2, 129.3, 130.2, 132.2, 135.2, 154.2, 156.3; LR-ESIMS: m/z = 256 + [MH] ; HR-ESIMS: m/z = 256.0970 (calcd. for C15H14NO3, 256.0968). S6 Electronic Supplementary Material (ESI) for Chemical Science This journal is © The Royal Society of Chemistry 2012 Acetophenone O-((benzyloxy)carbonyl) oxime - 5b Chloroformate Route: Prepared from benzyl chloroformate (0.45 cm3, 3.16 mmol), acetophenone oxime (0.355 g, 2.63 mmol) and pyridine (0.25 cm3, 3.16 mmol) to give a colourless crystalline powder, 0.648 g, yield = 87%. CDI One-Pot Route: Prepared from benzyl alcohol (0.50 cm3, 4.83 mmol), CDI (0.783 g, 4.83 mmol), acetophenone oxime (0.652 g, 4.83 mmol) and sodium hydride (0.035 g, 1.45 mmol) to give a colourless crystalline powder, 0.597 g, yield = 46%. CDI Two-Pot Route: Prepared from benzyl alcohol (0.50 cm3, 4.83 mmol), CDI (2.348 g, 14.5 mmol), acetophenone oxime (0.979 g, 7.25 mmol), sodium hydride (0.035 g, 1.44 mmol) to give a colourless crystalline powder, 0.861 g, yield = 63%. 1 M.p. = 53‒56 °C; H NMR (400 MHz, CDCl3, 294 K): = 2.39 (s, 3H, Hb), 5.31 (s, 2H, Ha), 7.36‒ 13 7.47 (m, 8H, HAr), 7.74 (d, J = 8.3 Hz, 2H, Hc); C NMR (100 MHz, CDCl3, 295 K): = 14.4, 70.2, 127.0, 128.6, 128.7 (× 2), 128.8, 130.6, 134.6, 134.9, 153.9, 162.7; LR-ESIMS: m/z = 270 + [MH] ; HR-ESIMS: m/z = 270.1126 (calcd. for C16H16NO3, 270.1125). 1 Benzyl 1H-imidazole-1-carboxylate - 4b: H NMR (400 MHz, CDCl3, 296 K): = 5.42 (s, 2H, Hd), 7.06 (d, J = 1.0 Hz, 1H, Hg), 7.11 (d, J = 1.0 Hz, 1H, Hf), 7.40‒7.46 (m, 5H, Ha,b,c), 8.15 (s, 1H, 13 He); C NMR (100 MHz, CDCl3, 297 K): = 69.9, 117.2, 128.8, 128.9, 129.2, 130.7, 134.0, 135.1, 137.2.
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