A general method to access CF3-substituted allenes from propargylic alcohols under Lewis acid catalysis in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as solvent is described. By tuning the reaction time and temperature, the obtained allenes rearrange to 1,3-biaryl-1-trifluoromethyl-1Hindenes. By tuning the structure of the propargylic alcohol substrates, a range of trifluoromethylated 2H-chromenes were successfully synthesized, with use of catalytic quantities of strong Brønsted acid in HFIP. The present method is therefore highly potent for synthesis of a number of potentially pharmaceutically interesting new trifluoromethylated compounds and produces water as the only stoichiometric byproduct.

Triterpenoid natural products from the Schisandraceae family have long presented a significant synthetic challenge. Lancifodilactone I, a member of the family not previously synthesized, was identified as a key natural product target, from which many other members could be synthesized. We envisaged that the core ring system of lancifodilactone I could be accessed by a strategy involving palladium-catalysed cascade cyclisation of a bromoenynamide, via carbopalladation, Suzuki coupling and 8π-electrocyclisation, to synthesize the core 7,8-fused ring system. Exploration of this strategy on model systems resulted in efficient syntheses of 5,6- and 5,8-fused systems in high yields, which represent the first such cyclisation where the ynamide nitrogen atom is ‘external’ to the forming ring system. The enamide functionality resident in the cascade cyclisation product was found to be less nucleophilic than the accompanying tri-/tetrasubstituted alkene(s), enabling regioselective oxidations. Application of this strategy to 7,6-, and 7,8-fused systems, and ultimately the ‘real’ substrate, was ultimately thwarted by the difficulty of 7-membered ring closure, leading to side product formation. Nevertheless, a tandem bromoenynamide carbopalladation, Suzuki coupling and 6/8π-electrocyclisation was shown to be a highly efficient tactic for the formation of bicyclic enamides, which may find applications in other synthetic contexts.