Dicarboxylic acids and their derivatives have a variety of applications in many fields such as polymers, pharmaceuticals, and metal-organic materials. Cyclobutanedicarboxylic acids (CBDAs) represent a family of promising diacids that can be synthesized by using photoreaction. It has been known for about a century that both CBDA-1 (α-truxillic acid) and CBDA-4 (β-truxinic acid) could be synthesized from two polymorphs: α- and β-trans-cinnamic acid, respectively. However, researchers had to take a detour to make CBDA-4 by turning trans-cinnamic acid into its p-nitrophenyl ester or 1,3-trimethylene diester for photodimerization, and then hydrolyzed the ester dimer back to CBDA-4. This is because that the metastable crystalline β-form (head-tohead packing) of trans-cinnamic acid is readily to transfer to the stable α- form (head-to-tail packing). The low energy barrier from the β-form to the α-form renders reliable synthesis of CBDA- 4 challenging because the β-form gives CBDA-4 after photodimerization and α-form leads to CBDA-1, which also explained the conflicting experimental results about CBDA-4 synthesis in the literature. In this presentation, we will show a facile and scalable preparation method of CBDA-4 accomplished by capturing and photodimerizing the metastable crystalline solid of trans-cinnamic acid. This synthetic approach builds a foundation for investigating the properties and applications of the useful diacid and its derivatives. The X-ray crystal structure of CBDA-4 was determined for the first time. The synthesis of a series of mono- and di-esters derived from CBDA-4, which have similar structure to the widely used phthalates, will also be discussed.

Scalable synthesis of a cyclobutane-1, 2-diacid and its derivatives from trans-cinnamic acid via photoreaction

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.