It has long been known that coumarins (α-pyrones) and xanthones (γ-pyrones) together form a large class of naturally occurring compounds exhibiting a wide range of biological activities. However, the interest of the scientific community for these secondary metabolites, as well as for their structural analogues, has never decreased since these “old compounds” are constantly generating promising—...

ortho-Quinone methides, arising from a formal [2+2] cycloaddition between arynes and DMF, were found to facilely undergo a [4+2] cycloaddition with ester enolates or ketenimine anions to produce diverse coumarins in a straightforward manner.

The coupling of coumarins with alkynes is described, which proceeds through a palladium-catalyzed cascade sequence. This process provides a new route to the synthesis of highly substituted cyclopentadiene fused chromones.

Four new guaianolides, sinodielides A-D (1-4), were isolated from Sinodielsia yunnanensis WOLFF together with a known polyacetylene, falcarindiol, and two known coumarins, bergapten and scopoletin. Their structures were established by spectral and X-ray analyses.

Benzo-, furo-, thieno-, and pyrido[f]coumarins were prepared by generating the 2H-pyran-2-one moieties from the oxidation of the corresponding 2H-pyran rings, which were formed in situ from the electrocyclization of cis-dienals.