Synlett
DOI: 10.1055/s-0036-1588571
letter
© Georg Thieme Verlag Stuttgart · New York

Preparation of Propargyl Amines in a ZnCl2–Dimethylurea Deep-Eutectic Solvent

Martin Obsta, Akriti Srivastavab, Sundarababu Baskaran*b, Burkhard König*a
We thank the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG 9209735) and DST (INT/FRG/DFG/P-44/2014) for financial support.
Further Information

Publication History

Received: 25 July 2017

Accepted after revision: 29 August 2017

Publication Date:
21 September 2017 (eFirst)

Abstract

The coupling of an aldehyde, an amine, and an alkyne to yield propargyl amines was performed in a deep-eutectic solvent composed of zinc chloride and dimethylurea. The deep-eutectic solvent acts simultaneously as catalyst and solvent giving access to a variety of propargyl amines, which were isolated in moderate to very good yields.

Supporting Information

 
  • References and Notes

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  • 24 General Procedure for the Synthesis of Propargyl Amines The aldehyde was added to the DES (for preparation of DES, see the Supporting Information), followed by the amine (1.5 equiv) and the alkyne (1.5 equiv), and the reaction was performed at 80 °C for 20 h. For workup, the hot reaction mixture was diluted with 2 mL water and extracted four times with 5 mL EtOAc. The combined organic layers were dried over Na2SO4, and the product was isolated applying flash column chromatography (gradient of EtOAC in PE). 4-​[1-​(4-​Iodophenyl)​-​3-​phenyl-​2-​propyn-​1-​yl]​-morpholine (5) 4-Iodobenzaldehyde (232 mg, 1.0 mmol) was reacted with morpholine (131 μL, 1.5 mmol) and phenylacetylene (165 μL, 1.5 mmol). The reaction was performed in 1 g of melt, prepared from 0.31 g ZnCl2 and 0.69 g DMU; yield 336 mg (82%). 1H NMR (300 MHz, CDCl3): δ = 7.73–7.69 (m, 2 H), 7.57–7.51 (m, 2 H), 7.43–7.40 (m, 2 H), 7.37–7.32 (m, 3 H), 4.74 (s, 1 H), 3.80–3.68 (m, 4 H), 2.63 (t, J = 4.5 Hz, 4 H). 13C NMR (75 MHz, CDCl3): δ = 137.8, 137.4, 131.9, 130.6, 128.5, 128.4, 122.7, 93.6, 89.0, 84.3, 67.1, 61.4, 49.9. ESI-MS: m/z calcd for C19H18INO [MH]+: 404.0512; found: 404.0533. EA (%, theoretical values in brackets): C, 56.50 (56.59); H, 4.36 (4.50); N, 3.38 (3.47).