Green chemistry topics are important additions to subjects normally offered at any level of chemistry education. As part of a continuing effort to further green the organic chemistry laboratory curriculum, aqueous and solventless Diels-Alder reactions between 2-furfuryl alcohol and maleimide were developed and resulted in good yields of endo and exo 3a,4,7,7a-tetrahydro-4-(hydroxymethyl)-4,7-epoxy-1H-isoindole-1,3(2H)-dione at room temperature and atmospheric pressure in the hands of students during a single four-hour laboratory period. Attempts to increase the reaction rates by heating above room temperature increased the exo:endo ratios significantly. Heating pure solid endo isomer at temperatures below 80 oC for 4 hours did not produce the exo isomer, but heating pure solid endo isomer above 100 oC produced the exo isomer exclusively in a quantitative yield. The thermal isomerization was studied using Diels-Alder adducts between several 2-substituted furans and maleimide to further investigate possible assistance by intramolecular hydrogen bonding.

Endo to exo thermal isomerization of a green Diels-Alder adduct

251st National Meeting (2016)

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