title: Synthesis of Furo[3,2-c]benzopyrans via an Intramolecular [4 + 2] Cycloaddition Reaction of o-Quinonemethides.
abstract: 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.
authors.affiliation: School of Chemistry and Chemical Engineering and Jiangsu Key Laboratory of Green Synthetic Chemistry for Functional Materials, Jiangsu Normal University , Xuzhou 221116, Jiangsu, China.
authors.forename: Li-Ming
authors.initials: LM
authors.lastname: Zhao
authors.affiliation: School of Chemistry and Chemical Engineering and Jiangsu Key Laboratory of Green Synthetic Chemistry for Functional Materials, Jiangsu Normal University , Xuzhou 221116, Jiangsu, China.
authors.forename: Ai-Li
authors.initials: AL
authors.lastname: Zhang
authors.affiliation: School of Chemistry and Chemical Engineering and Jiangsu Key Laboratory of Green Synthetic Chemistry for Functional Materials, Jiangsu Normal University , Xuzhou 221116, Jiangsu, China.
authors.forename: Hua-Shuai
authors.initials: HS
authors.lastname: Gao
authors.affiliation: School of Chemistry and Chemical Engineering and Jiangsu Key Laboratory of Green Synthetic Chemistry for Functional Materials, Jiangsu Normal University , Xuzhou 221116, Jiangsu, China.
authors.forename: Jie-Huan
authors.initials: JH
authors.lastname: Zhang