C- vs. N-Oxidations of Benzyltriazanes: Selective Access to Triazones, Azimines, and TriazenesWe thank the CNRS, CNES, ArianeGroup and Université C. Bernard-Lyon 1 for funding, including a doctoral stipend for AG. VJ thanks the CNES for a postdoctoral fellowship.
Received: 14 October 2017
Accepted after revision: 16 November 2017
22 January 2018 (online)
The oxidation of several benzyltriazanes has been studied. Routes to the selective formation of triazenes, azimines, and triazones via C- or N-oxidation (and rearrangement) were devised. The rich reactivity of triazanes shows that trinitrogen chains are interesting functions, whose reactivity has been overlooked despite their interest as 3-N building blocks.
References and Notes
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- 12 General Procedure for the Formation of Triazones The triazane (0.5 mmol) was dissolved in CH2Cl2 (4 mL) under N2 at rt K2CO3 (10 equiv) and lead(IV) acetate (1 equiv, 85%) were added at –78 °C. The cold bath was removed, and the reaction mixture was stirred for 30 min. The precipitate was filtered off and washed several times with CH2Cl2. The combined organics extracts were concentrated in vacuo and purified by column chromatography. Compound 2a: 1H NMR (400 MHz, CDCl3) δ: 1.50 and 1.58 (bs + s, 18H, t-Bu), 6.45 (s, 1H, NH), 7.35–7.39 (m, 3H, Ar), 7.71–7.75 (m, 2H, Ar), 7.92 (s, 1H, CH=N). 13C NMR (100 MHz, CDCl3) δ: 28.0 (Me), 82.3 (C-N), 82.9 (C-N), 127.6 (CH), 128.4 (CH), 129.6 (CH), 134.0 (C), 139.5 (CH=N), 151.6 (C=O), 153.8 (C=O). ESI-HRMS: m/z calcd [M+H]+: 336.1918; found: 336.1924 (1.8 ppm). IR (neat): ν = 1450, 1479, 1720, 2979, 3287 cm–1; mp 106°C, decomp: 159°C. General Procedure for the Formation of Triazenes or Azimines The triazane (0.5 mmol) was dissolved in EtOH (10 mL) under N2 at rt PhI(OAc)2 (2.2 equiv) was added at 0 °C, and the reaction mixture was stirred for 30 min at 0 °C. Water was then added, and the mixture was extracted three times with EtOAc. The combined organic extracts were washed with water and brine, dried over MgSO4, filtered, and the solvent removed. The triazenes (or azimine) were purified by chromatography. Compound 5: 1H NMR (400 MHz, CDCl3): δ = 1.52 (s, 18 H, t-Bu), 5.50 (s, CH2), 7.36–7.38 (m, 3 H, Ar), 7.48–7.51 (m, 2H, Ar). 13C NMR (100 MHz, CDCl3): δ = 28.2 (Me, t-Bu), 74.3 (CH2), 82.8 (C, t-Bu), 128.8 (CH, Ar), 129.0 (CH, Ar), 129.2 (CH, Ar), 132.3 (C, Ar), 156.7 (C=O). ESI-HRMS: m/z calcd [M + Na]+: 358.1737; found: 358.1720 (4.8 ppm). IR (neat): ν = 1467, 1690, 1704, 2927, 2975 cm–1; mp 145–146 °C, decomp.: 150 °C.
Triazenes are important compounds with a rich reactivity, see: