Epoxide apparent exchange reaction for the precise synthesis of epoxy resins.

Epoxy resins, exemplified by bisphenol A diglycidyl ether, are widely used in coatings, electronic packaging, and composite materials. However, the conventional NaOH-based synthesis lacks precision, as the harsh alkaline conditions inevitably induce side reactions such as oligomerization and hydrolysis, thereby compromising resin quality. Here, we report an organocatalytic epoxide apparent exchange reaction that enables the precise synthesis of bisphenol A diglycidyl ether from bisphenol A and epichlorohydrin, in which the β-chlorohydrin groups in the ether intermediates undergo apparent exchange with the epoxide groups in epichlorohydrin. Computational studies revealed that the alkoxide in situ generated from epichlorohydrin ring-opening facilitates a hydrogen-bonding-mediated proton-transfer pathway that induces the dehydrochlorination of the β-chlorohydrin groups, thereby forming the target epoxide groups. This approach provides broad applicability to the synthesis of most commercial epoxy resins. Furthermore, this mild method overcomes the structural limitations of the NaOH process, providing an alternative route to polyester-based epoxy resins and promoting the development of sustainable epoxy materials.