Acceleration of the Eschenmoser coupling reaction by sonication: efficient synthesis of enaminones

Abstract

Enaminones are commonly prepared by the Eschenmoser coupling reaction. The duration of the reaction is often long. Here, we describe how sonication can accelerate this reaction. The reaction conditions provide an efficient method for the coupling of primary, secondary and tertiary thioamides with a-bromocarbonyl compounds.

Magnetically separable γ-Fe2O3 nanoparticles: An efficient catalyst for acylation of alcohols, phenols, and amines using sonication energy under solvent free condition

“…The catalytic activity of synthesized magnetically recoverable γ-Fe 2 O 3 nanoparticles was checked for the acylation reaction using phenols, alcohols and amines with acetic anhydride under solvent free condition using sonication energy at room temperature (28 o C) (Scheme 1). The sonication energy has several advantages such as high efficiency, low waste, less energy requirement, it produces cavitation bubbles which increases the interaction between reactant and catalyst, accelerates the reaction speed, provides better mass and heat transfer efficiency compared to conventional heating, economic and easy operation [45,46].…”

Copper-catalyzed chemoselective cross-coupling reaction of thioamides and α-diazocarbonyl compounds: Synthesis of enaminones

“…The ESC also requires a long time for completion. [27][28][29][30] Furthermore, the ESC method is unsuccessful in coupling sterically hindered thioamides with α-halocarbonyl compounds. 14,31 Modified versions of the ESC reaction have emerged to overcome these shortcomings.…”

Scale-up of microdroplet reactions by heated ultrasonic nebulization

“…61,62 However, the coupling reaction oen requires a long reaction time. [63][64][65] Fig . 5a shows the reaction schematic of the Eschenmoser coupling reaction between 1-methylpyrrolidine-2-thione 9 and diethyl bromomalonate 10 to form the enaminone product 11.…”