Highly efficient synthesis of sustainable bisphenols from hydroxycinnamic acids

• Published in: RSC sustainability 2023-10, Vol.1 (7), p.1765-1772
• Main Authors: Zavala, Cristian E, Vest, Natalie A, Baca, Joshua E, Zhang, Derek D, McClain, K. Randall, Harvey, Benjamin G
• Format: Article
• Language: English
• ISSN: 2753-8125; 2753-8125
• DOI: 10.1039/d3su00175j

Three stilbene based bisphenols: ( E )-4,4′-(ethene-1,2-diyl)diphenol ( 1 ), ( E )-4,4′-(ethene-1,2-diyl)bis(2-methoxyphenol) ( 2 ), and ( E )-4,4′-(ethene-1,2-diyl)bis(2,6-dimethoxyphenol) ( 3 ) were synthesized from p -coumaric, ferulic, and sinapic acid, respectively. This was accomplished with a high-yielding two-step approach, which combined catalyst-free thermal decarboxylation of the cinnamic acids followed by olefin metathesis. The thermal decarboxylation proceeded in quantitative yield merely by refluxing the cinnamic acids in DMF under a nitrogen atmosphere. The resulting vinyl phenols were briefly isolated and then immediately subjected to olefin metathesis with a Grubbs-Hoveyda 2nd generation catalyst, which resulted in direct precipitation of the bisphenols from the reaction mixture. Overall yields of 1 , 2 , and 3 were 92, 88, and 85%, respectively, starting from the cinnamic acids. The compounds were isolated as pure solids without the need for crystallization or column chromatography. Bisphenol 1 was isomerized to the cis -isomer by irradiation with UV light. The resulting 80 : 20 cis  :  trans mixture exhibited a glass transition at low temperatures and a decreased melting temperature. To further expand the suite of bisphenols that can be produced from cinnamic acids, p -coumaric acid was directly converted into a 4-vinylphenol dimer by thermal decarboxylation/dimerization in a biphasic aqueous base/toluene solution to yield ( E )-4,4′-(but-1-ene-1,3-diyl)diphenol ( 4 ). The ability to efficiently produce bisphenols from abundant, low-cost, and easily sourced bio-based substrates holds great promise for the development of more sustainable polymers. A series of bisphenols were efficiently prepared from bio-based hydroxycinnamic acids via thermal decarboxylation followed by [Ru]-catalyzed olefin metathesis.