A novel and advantageous protocol for accessing carbamates through the known three-component coupling reaction involving carbon dioxide, amines, and alkyl halides is described. Employing mild conditions, simple experimental set-up, and immobilized DBU, this protocol addresses several drawbacks from the previous described methods. No classical purification procedures are necessary and the immobilized DBU can be recycled and reused several times.

Abstract

The present study highlights a novel and advantageous protocol for accessing carbamates through the well-established three-component coupling reaction involving CO₂, amines, and alkyl halides. By employing an immobilized organic base, operating under mild reaction conditions, an array of alkyl carbamates in yields of up to 95 % could be isolated. This approach offers a broad and versatile product scope, allowing for the facile modification of both the amine and alkyl halide reactants. Notably, the pioneering use of an immobilized organic base, specifically the polymer-supported 1,8-diazabicyclo[5.4.0]undec-7-ene (PS-DBU), in this three-component reaction eliminates the need for classical purification steps, streamlining the process. To ensure practicality and sustainability, extensive studies were conducted to verify the recovery and reusability of the polymer-supported DBU catalyst, which consistently maintained the high chemical yield of the carbamates across multiple cycles. Overall, this innovative protocol represents a significant advancement in carbamate synthesis, combining efficiency, generality, and the potential for DBU recycling.