Direct Synthesis of Organic Azides from Alcohols Using 2-Azido-1,3-dimethyl­imidazolinium Hexafluorophosphate

Abstract

Direct synthesis of organic azides from alcohols was developed. Azide transfer of 2-azido-1,3-dimethylimidazolinium hexafluorophosphate (ADMP) to alcohols proceeds to give the corresponding azides under mild reaction conditions, which were easily isolated because the byproducts are highly soluble in water.

Key words

ADMP - azides - diazo compounds - azide transfer - heterocycles

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• 10 Typical Procedure for the Synthesis of Organic Azides from Alcohols with ADMP (1; Table 1, Entry 6) To a solution of 4-phenylbenzyl alcohol (2a, 185 mg, 1.0 mmol) in THF (5 mL), 2-azide-1,3-dimethylimidazolinium hexafluorophosphate (1, 332 mg, 1.2 mmol), and DBU (0.15 mL, 1.3 mmol) were added at r.t., and the mixture was stirred for 10 min. The reaction was quenched with sat. aq NH₄Cl, and organic materials were extracted with CH₂Cl₂. The combined extracts were washed with brine, and then dried over anhyd Na₂SO₄. The solvent was removed in vacuo to afford the crude compounds that were purified by flash column chromatography (silica gel, hexane–EtOAc) to give pure 4-biphenylmethylazide (3a) in 93% yield as a white solid. Physical Data for 3a Mp 35–36 °C. ¹H NMR (400 MHz, CDCl₃): δ = 7.62–7.57 (m, 4 H), 7.48–7.42 (m, 2 H), 7.42–7.32 (m, 3 H), 4.36 (s, 2 H) ppm. ¹³C NMR (101 MHz, CDCl₃): δ = 141.3, 140.5, 134.4, 128.9, 128.7, 127.6, 127.5, 127.1, 54.5 ppm. IR (Nujol): 2098, 1463, 1253, 823 cm^–1. Anal. Calcd for C₁₃H₁₁N₃: C, 74.62; H, 5.30; N, 20.08. Found: C, 74.76; H, 5.42; N, 19.99