Silica-Functionalized CuI: An Efficient and Selective Catalyst for N-Benzylation, Allylation, and Alkylation of Primary and Secondary Amines in Water

Abstract

Silica-functionalized CuI has been reported as an efficient and selective catalyst for the selective mono-N- and N,N-dibenzylation, allylation, and alkylation of primary amines with benzylic, allylic, and alkyl halides using NaOH as base in aqueous medium. By changing the reaction temperature, mono- or di-benzylation, allylation, or alkylation could be achieved in good yield and selectivity. Secondary amines have also been benzylated, allylated, and alkylated under similar conditions. SiO₂-CuI has been characterized by Fourier transform–infrared, atomic absorption spectrometry, thermalgravimetric analysis, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, and found to be highly selective and recyclable under the reaction conditions.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]

GRAPHICAL ABSTRACT

Keywords:

• Aqueous conditions
• heterogeneous catalysis
• N-alkylations
• selectivity
• silica-functionalized CuI

ACKNOWLEDGMENTS

We are grateful to SAIF, Punjab University, Chandigarh, for SEM, TEM, and XRD; and the head, Institute Instrumentation Centre, Indian Institute of Technology, Roorkee, for AAS analysis.

Notes

^a Reaction was carried out by stirring a mixture of amine (0.5 mmol), halide (0.5 mmol), NaOH (2 mmol), TBAB (0.25 mmol), and SiO₂-CuI (0.1 g, 5 mol% Cu) at 15 °C in different solvents.

^b Yield refers to column chromatography yield.

^a Reaction was carried out by stirring a mixture of amine (0.5 mmol), halide (0.5 mmol), NaOH (2 mmol), TBAB (0.25 mmol), and SiO₂-CuI (0.1 g, 5 mol% Cu) at 15 °C in water (4 mL).

^b Yield refers to column chromatography yield.

^a Allylation was carried out at 70 °C.

^b Reaction was carried out by stirring a mixture of amine (0.5 mmol), halide (1 mmol), NaOH (2 mmol), TBAB (0.25 mmol), and SiO₂-CuI (0.1 g, 5 mol% Cu) at 70–100 °C in water (4 mL).

^c Isolated yield (entries 1–5), column chromatography yield (entries 6–12).

^a Reaction was carried out by stirring a mixture of amine (0.5 mmol), halide (0.5 mmol), NaOH (2 mmol), TBAB (0.25 mmol), and SiO₂-CuI (0.1 g, 5 mol% Cu) at 100 °C in water (4 mL).

^b Isolated yield (entries 1–4) and column chromatography yield (entries 5–11).

^a Reaction was carried out by stirring a mixture of amine (0.5 mmol), halide (0.5 mmol), NaOH (2 mmol), TBAB (0.25 mmol), and SiO₂-CuI (0.1 g, 5 mol% Cu) at 15 °C in water (4 mL).

^b Yield refers to column chromatography yield.