Recent Advances in Catalyst Development for Transesterification of Dialkyl Carbonates with Phenol

Abstract

Synthesis of diphenyl carbonate (DPC) from dimethyl carbonate (DMC) with phenol is the most prominent application of transesterification of dialkyl carbonates (DACs); this is a significant step for the nonphosgene manufacturing of polycarbonate, which is considered to be one of the best examples of green and sustainable transformations available on such a large scale. In the last decades, extensive efforts have been focusing on atom efficiency, increased safety, waste avoidance, and other process improvements for the transesterification synthesis of DPC. However, low product selectivity, separation, and catalyst deactivation remain bottlenecks of the process, despite recent significant progress. Therefore, the present interest focuses on rational design of highly efficient and stable catalysts. However, there is still a lack of a comprehensive summary on catalyst design and mechanism involved. Therefore, in this work, transesterification of DMC with phenol has been critically revised as a model case, to illustrate the structure–performance correlation and reaction pathways for transesterification with phenols. In this perspective, recent advances on experimental and investigations on rational design of heterogeneous catalysts, for facile liquid-phase reaction of DMC with phenol, have been systematically discussed, in terms of catalyst synthesis, surface characterization, and structure–function relationship. More importantly, plausible mechanisms for transesterification of DMC with phenol will be systematically discussed with the aim to provide insights into fundamental understanding on transesterification chemistry and improvement of activity, selectivity, and stability of these catalytic materials.

Selective C(aryl)–O bond cleavage in biorenewable phenolics

“…An alternative and attractive synthesis of aryl methyl carbonates would be a direct reaction of a phenol with dimethyl carbonate (DMC), obtainable from CO 2 and MeOH. 189 Although synthetically challenging, this would result in a 100% renewable leaving group. Furthermore, DMC is extremely cheap and produced in large scale.…”

Diphenyl Carbonate: Recent Progress on Its Catalytic Synthesis by Transesterification

“…The general transesterification reaction equation of phenol and DMC is [14,[16][17][18] shown by (1) in Figure 1: This reaction includes the following steps: DMC reacts with phenol to form methyl phenyl carbonate (MPC) through transesterification, shown by (2) in Figure 1. MPC and phenol are subjected to the transesterification reaction again to generate DPC, shown by (3) in Figure 1, or MPC undergoes a self-disproportionation reaction to generate DMC and DPC, shown by (4) in Figure 1.…”

“…The source of diphenyl carbonate is crucial in the transesterification process. Currently, the main production processes for diphenyl carbonate include the phosgene method and the transesterification method [13][14][15]. The phosgene method involves the generation of chloroformic acid benzyl ester from benzene and phosgene in a NaOH solution, which is further condensed with benzene to produce diphenyl carbonate.…”

One-Pot Nonisocyanate Synthesis of Sequence-Controlled Poly(hydroxy urethane)s from a Bis(six-membered cyclic carbonate) and Two Different Diamines

“…Although the sequence-controlled PUs have been synthesized via a solution- or solid-phase iterative stepwise approach, most of PUs currently used in industry result from the polyaddition of a diol (or polyol) with a harmful bifunctional (or polyfunctional) isocyanate that is usually prepared from highly toxic phosgene. In contrast, poly­(hydroxy urethane)­s (PHUs) that are PUs bearing hydroxyl groups at the side chains can be synthesized via an isocyanate-free approach, utilizing the ring-opening polyaddition of a bifunctional five- or six-membered cyclic carbonate with a diamine, which is an alternative synthetic route to PUs. − Furthermore, recent advances in the synthesis of such cyclic carbonates by the reactions of the corresponding polyols with transesterification agents, such as dialkyl carbonates and diphenyl carbonate (DPC) that can be prepared by phosgene derivative-free approaches, − and of bifunctional oxiranes with carbon dioxide have provided truly phosgene-free synthetic routes to PUs. − However, most of bifunctional cyclic carbonates synthesized so far require a flexible or semirigid linker to connect two cyclic carbonate moieties. − ,,− Therefore, if monomers are symmetric, the reactivities of the two cyclic carbonate groups connected by a linker are identical to each other and the ring-opening of one of these two ones in principle cannot influence on the reactivity of the other one, thus being unable to synthesize sequence-controlled PHUs from symmetric monomers by a standard polyaddition approach and even by sequential addition of different diamines to such bifunctional cyclic carbonates (Figure a). On the other hand, such a change in the reactivity is expected for a symmetric but “linkerless” bifunctional cyclic carbonate, namely, 2,4,8,10-tetraoxaspiro[5.5]­undecane-3,9-dione ( 1 ), of which two six-membered cyclic carbonate groups are mutually linked by the spiro carbon atom at the 6-position (Figure b), although little is known about its reactivity and its application to the PHU synthesis. − The spiro bis­(six-membered cyclic carbonate) 1 has already been prepared from the reaction of inexpensive pentaerythritol (PE) and diethyl carbonate in the presence of a base catalyst, which is a phosgene derivative-free approach but requires...…”