Intensification of heterogeneously catalyzed Suzuki-Miyaura cross-coupling reaction using ultrasound: Understanding effect of operating parameters

Abstract

Palladium-catalyzed Suzuki-Miyaura cross-coupling reaction is a significant reaction for obtaining industrially important products. The current research work deals with intensification of reaction of 4-bromoanisole and phenylboronic acid catalyzed with 5wt% Pd/C (5% by weight Pd supported on C available as commercial catalyst) using ultrasound and more importantly, without use of any additional phase transfer catalyst. Heterogeneous catalyst has been selected in the present work so as to harness the benefits of easy separation and the possible limitations of heterogeneous operation are minimized by introducing ultrasonic irradiations. The effect of operating parameters such as ultrasound power, temperature, catalyst loading and molar ratio on the progress of reaction has been investigated. It has been observed that an optimum power, temperature and catalyst loading exist for maximum benefits whereas higher molar ratio was found to be favourable for the progress of the reaction. Also, the use of ultrasound reduced the reaction time from 70min required in conventional approach to only 35min under conditions of frequency of 22kHz, power dissipation of 40W and catalyst loading as 1.5mol% (refers to total quantum of catalyst used in the work) in ethanol-water system under ambient conditions. The work also demonstrated successful results at ten times higher volume as compared to the normally used volumes in the case of simple ultrasonic horn. Overall, the work has successfully demonstrated process intensification benefits obtained due to the use of ultrasound for heterogeneously catalyzed Suzuki-Miyaura cross-coupling reaction.

Solvent effects in palladium catalysed cross-coupling reactions

“…Higher proportions of water in an aqueous-organic mixture can also inhibit the dispersion of Pd/C. 285 Suzuki reactions performed in DMAc are also assisted by the addition of water, but again too much water resulted in homocoupling (Scheme 63). 286 The ability of DMAc to reduce Pd(II) (as in Scheme 7) was suggested as contributing to the performance of this particular solvent.…”

The effect of high-energy environments on the structure of laccase-polymerized poly(catechol)

“…Ultrasound has been extensively used in enzyme-catalyzed biotransformations aiming to intensify the reaction processes and obtain higher yield of products in short periods of time [7][8][9][10]. Several works have been reporting laccase catalysis assisted by ultrasound however lacking information about the polymer structure obtained using differentiated devices [9,11,12].…”

Catalytic and biological valorization of a supramolecular mononuclear copper complex based 4‐aminopyridine

“…At first, we optimized the ultrasonic operating parameters. Thus, several parameters can be adjusted to influence the selectivity and the progress of the chemical reaction . The results obtained did not display any progress of the reaction, whose amplitude is less than 30% (Table , entry 1–3), and then by increasing to 40% the yield decreases, which accounts for the threshold or the physical limit of ultrasonic activation.…”