Polyethylene Glycol–Enhanced Chemoselective Synthesis of Organic Carbamates from Amines, CO₂, and Alkyl Halides

Abstract

An efficient and environmentally benign method for the synthesis of organic carbamates was developed. Amines, CO₂, and alkyl halides underwent a three-component reaction with the aid of K₂CO₃ and polyethylene glycol (PEG, MW = 400), affording the organic carbamates under ambient conditions. PEG could presumably act as a solvent and phase-transfer catalyst (PTC). Notably, the presence of PEG could also depress the alkylation of both the amine and the carbamate, thus resulting in enhanced selectivity toward the target carbamate.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.

Keywords:

• Amine
• carbon dioxide
• organic carbamate
• polyethylene glycol
• potassium carbonate

ACKNOWLEDGMENTS

Financial support from the National Natural Science Foundation of China (Grant Nos. 20421202, 20672054 and 20872073), the 111 Project (B06005), and the Committee of Science and Technology of Tianjin is gratefully acknowledged.

Notes

^a Reaction conditions: dibutylamine (2 mmol), 1-bromobutane (4 mmol), PEG400 (10 mL), base (4 mmol), CO₂ (1 atm), and biphenyl (60 mg, as internal standard), rt, 24 h.

^b Determined by GC using biphenyl as internal standard.

^c 1,4-Diazabicyclo[2.2.2]octane.

^a Reactions were conducted with dibutylamine (2 mmol), 1-bromobutane (4 mmol), solvent (10 mL), K₂CO₃ (4 mmol), CO₂ (1 atm), and biphenyl (60 mg, as internal standard) at rt for 24 h.

^b Determined by GC using biphenyl as internal standard.

^c N-Methylpyrrolidone.

^d 373 K for 6 h.

^a Reactions were conducted with dibutylamine (2 mmol), 1-bromobutane (4 mmol), PEG400 (10 mL), biphenyl (60 mg, as internal standard), and K₂CO₃ (4 mmol).

^b Determined by GC using biphenyl as internal standard.

^a Reactions were conducted with amine (2 mmol), halide (4 mmol), PEG400 (10 mL), biphenyl (60 mg, as internal standard), K₂CO₃ (4 mmol), and CO₂ (1 atm), at rt for 48 h.

^b Conversion and yield were determined by GC using biphenyl as internal standard. Data in parentheses refer to the isolated yield.