Copper(II)-Promoted Regioselective Synthesis of 1,4-Disubstituted 1,2,3-Triazoles in Water

Abstract

A high-yielding synthesis of 1,2,3-triazole with cheaply available Cu(OAc)₂ without any additional reducing agents is ­explored, which provides an exclusive 1,4-regioselectivity at ­ambient conditions in an environmentally benign solvent - water.

Key words

Cu(II) catalyst - regioselective - 1,2,3-triazole - water

References and Notes

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16

Typical Procedure for the Synthesis of 1,2,3-Triazoles
To the stirred solution of alkyne (1.2 mmol) and copper catalyst (20 mol%) in H₂O (3 mL), was added alkyl azide (1.0 mmol) in one portion at r.t. After 20 h of stirring, the precipitated product was extracted with EtOAc (3 × 5 mL) and the organic extract was dried. The crude product was subjected to column chromatography to yield the desired product. The products were characterized by ¹H NMR.
Compound 1a: ¹H NMR (CDCl₃): δ = 5.55 (s, 2 H), 7.25-7.37 (m, 8 H), 7.58 (s, 1 H), 7.75 (d, 2 H, J = 8.30 Hz). Compound 2a: ¹H NMR (CDCl₃): δ = 2.36 (s, 3 H), 5.55 (s, 2 H), 7.14-7.37 (m, 7 H), 7.55 (s, 1 H), 7.64 (d, 2 H, J = 8.3 Hz). Compound 3a: ¹H NMR (CDCl₃): δ = 3.83 (s, 3 H), 5.52 (s, 2 H), 6.69 (m, 1 H), 7.19-7.38 (m, 8 H), 7.58 (s, 1 H). Compound 4a: ¹H NMR (CDCl₃): δ = 3.12 (br, 1 H), 4.69 (s, 2 H), 5.48 (s, 2 H), 7.18-7.38 (m, 6 H). Compound 5a: ¹H NMR (CDCl₃): δ = 1.52 (s, 6 H), 4.20 (br, 1 H), 5.39 (s, 2 H), 7.21-7.36 (m, 6 H). Compound 6a: ¹H NMR (CDCl₃): δ = 1.90 (s, 3 H), 2.93 (br, 1 H), 5.43 (s, 2 H), 7.15-7.42 (m, 11 H).