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The first asymmetric convergent total synthesis of four isomers of proposed structures of cryptorigidifoliol K (1a, 1b, 1c, and 1d) has been achieved from commercially available starting materials. The key steps in this synthesis involve tandem isomerization followed by a C-O and C-C bond-forming reaction for the construction of trans-2,6-disubstituted dihydropyran, iodolactonization, isomerization of terminal alkene, and cross-metathesis reaction. The large discrepancies in the spectroscopic data (H NMR) of synthetic cryptorigidifoliol K from the natural product suggest that the structure of the natural cryptorigidifoliol K requires revision.

Complementary to Catellani-type reactions and 1:1 coupling of six-membered halo­(hetero)­arenes and norbornene (NBE) derivatives, Pd-catalyzed 1:2 coupling of five-membered haloheteroarenes with NBEs was achieved to afford rigid nonplanar heterocycles. Pyrazole, thiophene, furan, and indole underwent exo- and trans-selective annulation. Two strained alkene groups of the resulting products were further manipulated to afford 1-alkylindazoles and ladder polymers. The type of heteroarenes and position of halides along with the choice of ligands and bases were critical to set a preference between C–H annulation and Catellani reactions, which will be useful for the development of Pd-catalyzed, NBE-mediated reactions of heteroarenes.