Electronic effects on a one-pot aromatization cascade involving alkynyl-Prins cyclization, Friedel-Crafts alkylation and dehydration to tricyclic benzo[f]isochromenesElectronic supplementary information (ESI) available: Copies of 1H and 13C NMR spectra of starting alkynediols as well as benzo[f]isochromene products, HPLC traces of chiral products, abbreviated X-ray information for two products and experimental procedures/data. CCDC 1554998 and 1554999. For ESI and crystallographic data in CIF or

A three-step domino reaction between 1-aryl-3-hexyne-2,6-diol derivatives and aldehydes is used to construct tricyclic 1,4-dihydro-2 H -benzo[ f ]isochromenes. The cascade is initiated by BF 3 ·OEt 2 and involves alkynyl-Prins cyclization, Friedel-Crafts alkenylation, and dehydration/aromatization to create a new, central aromatic ring and eliminate 2 equiv. of water. Electron-donating substituents on the aryl ring of the 1-aryl-3-hexyne-2,6-diols significantly increase overall yields as do electron-rich aldehyde reaction partners. For 2,4-disubstituted 2 H -benzo[ f ]isochromene products, diastereoselectivities in the alkynyl-Prins reaction are ∼1.4 : 1 in favor of the cis -diastereomer. The stereochemistry of one cis -product was verified by X-ray crystallographic analysis and a second structure was also verified by X-ray analysis. A short, efficient cyclization/aromatization cascade affords tricyclic 1,4-dihydro-2 H -benzo[ f ]isochromenes. Electronic factors suggest concerted alkynyl-Prins and Friedel-Crafts reactions in the sequence.