Palladium-Catalyzed Regioselective ortho-Acetoxylation of 3-Aryl-1,2,4-Benzotriazines via C–H Activation

Abstract

A highly regioselective ortho-acetoxylation has been achieved in the presence of 10 mol% Pd(OAc)₂ and a stoichiometric amount of PhI(OAc)₂ in a mixture of acetic anhydride and acetic acid via C–H activation to produce the corresponding acetoxy-substituted 3-aryl-1,2,4-benzotriazines derivatives in good yields.

Key words

palladium catalyst - acetoxylation - C–H activation - 3-aryl-1,2,4-benzotriazines

• References and Notes


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• 17 Typical Procedure for the Preparation of 2-{Benzo[e][1,2,4]triazin-3-yl}phenyl Acetate A test tube was charged with 1a (0.2 mmol), Pd(OAc)₂ (0.02 mmol), and PhI(OAc)₂ (0.22 mmol). Then AcOH–Ac₂O (1 mL) was added to the reaction system. The reaction was stirred at 100 °C under air for 6 h. After cooling to r.t., the solvent was diluted with EtOAc (10 mL) and washed with brine (5 mL) and dried over anhyd Na₂SO₄. After the solvent was evaporated in vacuo, the residues were purified by column chromatography, eluting with PE–EtOAc to afford 38 mg (72%) pure 2a as yellow solid, mp 102–105 °C. ¹H NMR (400 MHz, CDCl₃): δ = 8.55 (d d, J = 8.0 Hz, 1.6 Hz, 2 H), 8.07–8.05 (m, 1 H), 8.01–7.97 (m, 1 H), 7.89–7.85 (m, 1 H), 7.62–7.58 (m, 1 H), 7.51–7.47 (m, 1 H), 7.27 (d d, J = 8.0 Hz, J = 1.6 Hz, 1 H), 2.39 (s, 3 H). ¹³C NMR (100 MHz, CDCl₃): δ = 169.9, 159.3, 149.7, 145.8, 140.6, 135.6, 132.1, 132.1, 130.6, 129.5, 128.9, 128.6, 126.5, 124.2, 21.2. IR (neat): 3070, 2924, 2853, 1768, 1514, 1458, 1372, 1322, 1198, 1100, 1012, 769 cm^–1. ESI-HRMS: m/z calcd for C₁₅H₁₁N₃O₂ [M + H]⁺: 266.0930; found: 266.0922.