A set of coumarin-fused electron-deficient 1,3-dienes was synthesized, which differ in the nature of the electron-withdrawing group (EWG) at the terminus of the diene unit and (when EWG = CO(2)Me) the nature and position of substituents. These dienes reacted with the enamine derived from cyclopentanone and pyrrolidine to afford the corresponding cyclopenteno-fused 6H-dibenzo[b,d]pyran-6-ones, most likely via a domino inverse electron demand Diels-Alder (IEDDA)/elimination/transfer hydrogenation sequence. The parent diene (EWG = CO(2)Me, no substituents) was reacted with a range of electron-rich dienophiles (mostly enamines) to afford the corresponding 6H-dibenzo[b,d]pyran-6-ones or their nondehydrogenated precursors, which were aromatized upon treatment with a suitable oxidant. The enamines could either be synthesized prior to the reaction or generated in situ. The syntheses of 30 dibenzopyranones are reported.

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Many of the current issues facing humans are geologic in nature. Whether the issue is mitigating the impact of geologic hazards, reducing air and water pollution, managing the energy of mineral resources, or minimizing the impact of anthropogenic global climate change, we require a geosciences-literate population. This is crucial to developing policies to best address these issues and to voting to implement such policies. In this article, we introduce a novel strategy for teaching geoscience content, as well as the nature of science, to a diverse audience: the historical case study. Essentially, the historical case studies "braid" the separate strands of history, inquiry, and modelbased learning into a narrative, thus allowing students to experience science in the making. This is in contrast to ready-made science as traditionally taught. We discuss the generations of the cases, summarize their content, and describe their implementation in multiple contexts of different courses. We also provide insights from the undergraduate researchers who developed the cases, the instructors who implemented them, and some preliminary data on student knowledge development concerning both geoscience content and nature of science. The cases are available online and open to the public. We welcome any feedback you wish to share.

In some cases, the dihydro analogues are obtained which can smoothly be converted into the title compounds by treatment with DDQ.