Synthesis of Furo[3,2‑c]benzopyrans via an Intramolecular [4 + 2] Cycloaddition Reaction of o‑Quinonemethides

An intramolecular [4 + 2] cycloaddition reaction of o-quinonemethides generated from salicylaldehydes and α-prenylated alcohols is described. In the presence of a catalytic amount of benzenesulfonic acid (BSA), the reaction proceeded smoothly in EtOH to afford furo­[3,2-c]­benzopyrans through a thre...

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Bibliographic Details
Published in:Journal of organic chemistry 2015-10, Vol.80 (20), p.10353-10358
Main Authors: Zhao, Li-Ming, Zhang, Ai-Li, Gao, Hua-Shuai, Zhang, Jie-Huan
Format: Article
Language:English
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Summary:An intramolecular [4 + 2] cycloaddition reaction of o-quinonemethides generated from salicylaldehydes and α-prenylated alcohols is described. In the presence of a catalytic amount of benzenesulfonic acid (BSA), the reaction proceeded smoothly in EtOH to afford furo­[3,2-c]­benzopyrans through a three-bond forming process in moderate to excellent yields with high diastereoselectivity. This reaction provides a simple and straightforward protocol to efficiently construct furo­[3,2-c]­benzopyran skeletons. A possible mechanism involving hemiacetal formation/hetero-Diels–Alder reaction is proposed to rationalize the observed results.
ISSN:0022-3263
1520-6904
DOI:10.1021/acs.joc.5b01641