Acylation and Related Reactions under Microwaves. 5. Development to Large Laboratory Scale with a Continuous-Flow Process

Abstract

Iron(III) chloride-catalyzed Friedel-Crafts acylation and sulfonylation of aromatics have been carried out using a continuous-flow microwave (MW) reactor. The MW applicator is a monomode waveguide fitted with power and temperature controls. The flow-through system operates at atmospheric pressure, and homogeneous conditions were ensured by using an excess of the aromatic. Factors that influence the reaction yield (MW power, ratio and flow rate of reactants) were optimized for two different types of substrate, two polar aromatic ethers, anisole (1) and phenetole (2), and a nonpolar arene, mesitylene (3). Although the energy yield was mainly influenced by the nature of the aromatic, the temperature necessary to achieve a high yield was reached in all cases. Methoxybenzophenone (7), 4-chloroethoxybenzophenone (8), and mesityl phenyl sulfone (9) were obtained from 1-3 and the corresponding acid chloride in 85-95% yield with a 1.2 L h -1 flow rate.

Microwave Synthesis of Nanoporous Materials

“…Several other similar continuous organic synthesis microwave reactors have been reported. [152][153][154][155] There are few examples of continuous microwave reactors for the synthesis of inorganic materials, namely porous oxides such as zeolites. Braun et al [156] described the synthesis of AlPO 4 zeolites using a continuous tube reactor.…”

Large-scale microwave-assisted ring-opening polymerization of ɛ-caprolactone

“…With reference to the successful small-scale examples, the larger scale microwaveassisted synthesis technology that can economically provide product on a multikilogram scale (or even higher) need to be developed for making it to become widespread technology in the future. Actually, for the ability of the direct homogenous heating of the reaction mixtures under microwave irradiation to facilitate direct scaling without heat and mass transport issues [7], several reports have demonstrated the feasibility of direct scaling reaction conditions from small-scale single-mode (0.5-5 mL) to larger scale batch modes (10-500 mL), such as multimode [8][9][10][11][12][13][14], monomode [15,16] and continuous-flow microwave reactors [17][18][19][20], without reoptimization of the reaction conditions. The larger scale microwave-assisted polymerizations (250-400 mL) have also been performed in domestic microwave ovens that equipped with reflux condensers [21,22].…”

Efficient and General Continuous‐Flow Hydroarylation and Hydroalkylation of Styrenes

“…The hydroarylation of halo-substituted styrenes with anisole was achieved under CF-MW conditions and the diarylethane products were obtained in good yields (71-88%; Table 3, entries [2][3][4][5]. Similarly, the reaction of 4-methyl-substituted styrene with anisole 2c also proceeded well providing the product in 89% yield (Table 3, entry 8).…”

“…[1] Scale-up of the reaction can be achieved by either running a single reactor for extended periods of time or by running several reactors in parallel. [2] Moreover, microwave technology has been incorporated into flow processes providing faster, cleaner and more selective reactions with higher yields as compared to traditional batch methods. [3][4][5] Thus, chemists in industry and in academia have begun to focus on reactor design and the development of new flow processes.…”