Solid Acid Catalysts for the Hock Cleavage of Hydroperoxides

Abstract

The oxidation of cumene and following cleavage of cumene hydroperoxide (CHP) with sulfuric acid (Hock rearrangement) is still, by far, the dominant synthetic route to produce phenol. In 2020, the global phenol market reached a value of 23.3 billion US$ with a projected compound annual growth rate of 3.4% for 2020–2025. From ecological and economical viewpoints, the key step of this process is the cleavage of CHP. One sought-after way to likewise reduce energy consumption and waste production of the process is to substitute sulfuric acid with heterogeneous catalysts. Different types of zeolites, silicon-based clays, heteropoly acids, and ion exchange resins have been investigated and tested in various studies. For every type of these solid acid catalysts, several materials were found that show high yield and selectivity to phenol. In this mini-review, first a brief introduction and overview on the Hock process is given. Next, the mechanism, kinetics, and safety aspects are summarized and discussed. Following, the different types of heterogeneous catalysts and their performance as catalyst in the Hock process are illustrated. Finally, the different approaches to substitute sulfuric acid in the synthetic route to produce phenol are briefly concluded and a short outlook is given.

Tandem InCl3-promoted hydroperoxide rearrangements and nucleophilic additions, a straightforward entry to benzoxacycles

“…The oxidative cleavage of organic hydroperoxides (Hock rearrangement 1 ) and related peresters (Criegee rearrangement 2 ) constitutes a straightforward route to carbonyl and phenol derivatives. 3 Important applications of the Hock cleavage concern the industrial cumene process, which allows the synthesis of millions tons of phenol and acetone each year (Scheme 1a), 4,5 and the synthesis of artemisinin, a major antimalarial compound. 6 It was also used to transform complex terpenoids, like cholesterol 7 or diterpenic acids, 8 in a bio-inspired manner.…”

“…H2SO4) and zeolithes. 4,5 However, there have been scarce systematic studies on the catalyst scope and applications. 3,9,17 Interestingly, the selectivity of the Hock and Criegee rearrangements is strongly influenced by strain relief 18 and by the electronic properties of substituents.…”

Traveling across Life Sciences with Acetophenone—A Simple Ketone That Has Special Multipurpose Missions

“…Almost 50 years ago, Sanders et al [ 6 ] appropriately analyzed eight possible syntheses of acetophenone ( 1 ) that could attain commercial status. Among them, the acid-catalyzed Friedel–Crafts acetylation of benzene ( 4 ) with acetic anhydride or acetyl chloride (method A) [ 62 ], the oxidation process of cumene ( 5 ), known as the Hock process (for phenol and acetone production), based on the decomposition of cumene hydroperoxide ( 6 ) under acid catalysis conditions [ 63 , 64 , 65 ] (method B), and the catalytic liquid-phase oxidation of ethylbenzene ( 7 ) with oxygen from air [ 66 ], giving the required acetophenone as the main product (together with 1-phenylethanol) through ethylbenzene hydroperoxide ( 8 ) (method C), are still the main procedures in the modern acetophenone industry ( Figure 4 ).…”

Tandem InCl3-promoted hydroperoxide rearrangements and nucleophilic additions, a straightforward entry to benzoxacycles

“…The oxidative cleavage of organic hydroperoxides (Hock rearrangement 1 ) and related peresters (Criegee rearrangement 2 ) constitutes a straightforward route to carbonyl and phenol derivatives. 3 Important applications of the Hock cleavage concern the industrial cumene process, which allows the synthesis of millions tons of phenol and acetone each year (Scheme 1a), 4,5 and the synthesis of artemisinin, a major antimalarial compound. 6 It was also used to transform complex terpenoids, like cholesterol 7 or diterpenic acids, 8 in a bio-inspired manner.…”

“…H2SO4) and zeolithes. 4,5 However, there have been scarce systematic studies on the catalyst scope and applications. 3,9,17 Interestingly, the selectivity of the Hock and Criegee rearrangements is strongly influenced by strain relief 18 and by the electronic properties of substituents.…”