Issue 36, 2017

Electronic effects on a one-pot aromatization cascade involving alkynyl-Prins cyclization, Friedel–Crafts alkylation and dehydration to tricyclic benzo[f]isochromenes

Abstract

A three-step domino reaction between 1-aryl-3-hexyne-2,6-diol derivatives and aldehydes is used to construct tricyclic 1,4-dihydro-2H-benzo[f]isochromenes. The cascade is initiated by BF3·OEt2 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 2H-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.

Graphical abstract: Electronic effects on a one-pot aromatization cascade involving alkynyl-Prins cyclization, Friedel–Crafts alkylation and dehydration to tricyclic benzo[f]isochromenes

Supplementary files

Article information

Article type
Paper
Submitted
10 Jun 2017
Accepted
10 Aug 2017
First published
11 Aug 2017

Org. Biomol. Chem., 2017,15, 7584-7593

Electronic effects on a one-pot aromatization cascade involving alkynyl-Prins cyclization, Friedel–Crafts alkylation and dehydration to tricyclic benzo[f]isochromenes

R. J. Hinkle, Y. Chen, C. P. Nofi and S. E. Lewis, Org. Biomol. Chem., 2017, 15, 7584 DOI: 10.1039/C7OB01412K

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