Sodium Hydride Induced N-Arylation of Diisopropyl Azodicarboxylate by Aryl Trifluoromethanesulfonates

Abstract

A method for intermolecular N-arylation of the anionic species derived from diisopropyl azodicarboxylate and sodium hydride by aryl trifluoromethanesulfonates, in the presence of a ligand-free copper(I) oxide catalyst at 80 °C in N,N-dimethylformamide, is reported. A variety of functionalized aryl triflouromethanesulfonates were efficiently coupled by this method.

Key words

C–N cross-coupling - aryl trifluoromethanesulfonates - diisopropyl azodicarboxylate - copper(I) oxide

• References and Notes

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Reviews:
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• 12 Typical Procedure for the Preparation of Aryl Hydrazides 3 To a stirred solution of DIAD (1.2 mmol) in DMF (2 mL) at 0 °C, NaH (0.05 g, 1.2 mmol) was added in portions over 20 min. Then, the aryl O-triflate (1.0 mmol), LiI (134 mg, 1mmol), and Cu₂O (15 mg, 0.1 mmol) were added to the reaction mixture, which was stirred at 80 °C for 8 h under N₂. The reaction was cooled and quenched by adding CH₂Cl₂ (2 mL) and sat. aq NH₄Cl (3 mL). The mixture was stirred for an additional 30 min, and two layers were separated. The aqueous layer was extracted with CH₂Cl₂ (3 × 2 mL), the combined organic layers were dried over MgSO₄, filtered, and concentrated in vacuo. The residue was purified by chromatography (silica gel; hexane–EtOAc, 3:1) to give the product. Spectroscopic analyses of all derivatives except 3d and 3m have been reported.¹¹ Diisopropyl 1-o-Tolylhydrazine-1,2-dicarboxylate (3d) Yellow solid; mp 101–103 °C; yield: 0.21 g (72%). IR (KBr): ν_max = 3242, 1541, 1518, 1330, 1140 cm^–1. ¹H NMR (500.1 MHz, CDCl₃): δ = 1.16 (6 H, d, ³ J = 7.1 Hz, 2 Me), 1.25 (6 H, d, ³ J = 7.0 Hz, 2 Me), 2.33 (3 H, s, Me), 4.97–4.99 (2 H, m, 2 CHO), 7.06 (1 H, br s, NH), 7.19–7.22 (3 H, m, 3 CH), 7.44 (1 H, d, ³ J = 7.8 Hz, CH). ¹³C NMR (125.7 MHz, CDCl₃): δ = 21.1 (2 Me), 21.4 (2 Me), 26.1 (Me), 68.9 (CHO), 70.1 (CHO), 113.1 (CH), 119.2 (CH), 126.3 (CH), 129.2 (CH), 130.9 (C), 140.5 (C), 155.7 (C=O), 156.1 (C=O). MS: m/z (%) = 294 (4 [M⁺], 235 (57), 192 (42), 177 (40), 133 (100), 102 (76), 58 (34), 44 (28). Anal. Calcd (%) for C₁₅H₂₂N₂O₄ (294.35): C, 61.21; H, 7.53; N, 9.52. Found: C, 59.89; H, 7.59; N, 9.59. Diisopropyl 1-(2-Chlorophenyl)hydrazine-1,2-dicarboxylate (3m) Colorless solid; mp 103–106 °C; yield 0.24 g (76%). IR (KBr): ν_max = 3286, 1564, 1518, 1332, 1136 cm^–1. ¹H NMR (500.1 MHz, CDCl₃): δ = 1.13 (6 H, d, ³ J = 6.9 Hz, 2 Me), 1.26 (6 H, d, ³ J = 7.0 Hz, 2 Me), 4.98–5.01 (2 H, m, 2 CHO), 7.17 (1 H, br s, NH), 7.46–7.53 (2 H, m, 2 CH), 7.62–7.67 (2 H, m, 2 CH). ¹³C NMR (125.7 MHz, CDCl₃): δ = 21.9 (2 Me), 22.3 (2 Me), 70.1 (CHO), 71.0 (CHO), 123.8 (CH), 128.1 (CH), 131.6 (CH), 132.6 (CH), 133.0 (C), 139.4 (C), 154.3 (C=O), 156.0 (C=O). MS: m/z (%) = 314 (1) [M⁺], 225 (12), 212 (53), 197 (45), 152 (100), 102 (64), 111 (12), 58 (35), 44 (19). Anal. Calcd (%) for C₁₄H₁₉ClN₂O₄ (314.76): C, 53.42; H, 6.08; N, 8.90. Found: C, 53.79; H, 6.04; N, 8.98.