Mechanistic Insights into the Kinetic and Regiochemical Control of the Thiol-Promoted Catalytic Synthesis of Diphenolic Acid

Challenges and Opportunities in the Catalytic Synthesis of Diphenolic Acid and Evaluation of Its Application Potential

Diphenolic acid, or 4,4-bis(4-hydroxyphenyl)pentanoic acid, represents one of the potentially most interesting bio-products obtainable from the levulinic acid supply-chain. It represents a valuable candidate for the replacement of bisphenol A, which is strongly questioned for its toxicological issues. Diphenolic acid synthesis involves the condensation reaction between phenol and levulinic acid and requires the presence of a Brønsted acid as a catalyst. In this review, the state of the art related to the catalytic issues of its synthesis have been critically discussed, with particular attention to the heterogeneous systems, the reference benchmark being represented by the homogeneous acids. The main opportunities in the field of heterogeneous catalysis are deeply discussed, as well as the bottlenecks to be overcome to facilitate diphenolic acid production on an industrial scale. The regioselectivity of the reaction is a critical point because only the p,p'-isomer is of industrial interest; thus, several strategies aiming at the improvement of the selectivity towards this isomer are considered. The future potential of adopting alkyl levulinates, instead of levulinic acid, as starting materials for the synthesis of new classes of biopolymers, such as new epoxy and phenolic resins and polycarbonates, is also briefly considered.

A guide towards safe, functional and renewable BPA alternatives by rational molecular design: structure–property and structure–toxicity relationships

Putting the pieces together: a guide for rational molecular design of safe, functional and renewable BPA alternatives.

Synthesis of 9,9-bis(4-hydroxyphenyl) fluorene catalyzed by bifunctional ionic liquids

A series of bifunctional ionic liquids (BFILs) containing sulfonic acid (–SO3H) and sulfhydryl groups (–SH) were synthesized, and their catalytic performance in the condensation reaction of 9-fluorenone and phenol were studied.

Condensation of 9-fluorenone and phenol using an ionic liquid and a mercapto compound synergistic catalyst

A SO₃H-functionalized ionic liquid and thiol co-catalyst synergistically catalyze the condensation reaction of 9-fluorenone with phenol.

Evaluation of Estrogenic Activity of Novel Bisphenol A Alternatives, Four Bioinspired Bisguaiacol F Specimens, by in Vitro Assays

Alternatives to bisphenol A (BPA), such as lignin-inspired bisguaiacol F (BGF), are of interest for food contact materials due to increasing evidence of estrogenic activity (EA) and exposure-correlated harmful effects of BPA and its analogues. BGF has similar thermal and mechanical properties to BPA, but contains additional methoxy substituents that may significantly reduce its endocrine disruption potential. In this study, the EA of four BGF samples with different regioisomer ratios was quantified relative to 17β-estradiol at ten concentrations by using two in vitro assays: MCF-7 cell proliferation and VM7Luc4E2 transactivation (TA). The results suggest BGF mixtures with higher molar ratios of p, p'-BGF and o, p'-BGF regioisomers exhibited lower EA than BPA, while BGF samples containing higher molar ratios of m, p'-BGF had no detectable EA over a wide range of test concentrations. These findings suggest the potential of BGF as a viable alternative to BPA for use in more environmentally friendly materials.

Zeolites as sustainable catalysts for the selective synthesis of renewable bisphenols from lignin-derived monomers

Alternative biobased bisphenols from lignocellulosic biomass are not only favorable to reduce the environmental impact of current petroleum-derived plastics, but they can be simultaneously beneficial for health issues related to bisphenol A (BPA). Additionally, conventional BPA synthesis entails a large excess of unrecoverable homogeneous acid catalyst (e.g., HCl) or unrecyclable thermolabile sulfonated resins. In this report, zeolites are proposed as recoverable and thermally stable solid acids for the Brønsted-acid-catalyzed condensation between 4-methylguaiacol and formaldehyde to selectively produce renewable bisphenols. It is found that the Brønsted-acid-site density plays a pivotal role for catalyst performance. In particular, the cheap and environmentally friendly FAU 40 exhibits outstanding activity (turnover frequency of 496 h^-1 ) and selectivity (>95 %), outperforming even the best benchmark catalyst. Additionally, the zeolite can be easily recycled without activity loss after regeneration by coke burn-off. The catalytic zeolite system also seems very promising for other lignin-derived alkylphenols, alkylguaiacols, and alkylsyringols.

Water-soluble sulfonated hyperbranched poly(arylene oxindole) catalysts as functional biomimics of cellulases

A new polymer acid catalyst, sulfonated hyperbranched poly(arylene oxindole), 5-OH–SHPAO, was prepared for selective cellulose hydrolysis.