P(NMe<sub>2</sub>)<sub>3</sub>-Mediated Reductive Intramolecular Annulation of Benzoylformates Tethered with a Trisubstituted Alkene Unit and Synthesis of 2,2-Disubstituted 2<i>H</i>-Chromenes
Jiayong Zhang, Yuhe Qiu, Biao Zhang, Zhiqiang Huang, Zhengjie He
Abstract
In this report, a P(NMe2)3-mediated reductive intramolecular annulation reaction has been developed with benzoyl formates bearing a trisubstituted alkene unit. It provides a facile synthesis of highly functionalized 2,2-disubstituted 2H-chromenes with a broad substrate scope and high efficiency. Experimental results suggest this annulation reaction proceeds via a cascade of alkene isomerization/vinyl o-quinone methide formation/6π-electrocyclization. As a key intermediate, the vinyl-substituted o-quinone methide is presumably generated by a Kukhtin–Ramirez adduct initiated O → C vinyl migration.
Topics & Concepts
AnnulationChemistryAlkeneIntramolecular forceAdductQuinone methideIsomerizationMedicinal chemistryCascade reactionStereochemistryCombinatorial chemistryOrganic chemistryQuinoneCatalysisSynthesis of Indole DerivativesCatalytic C–H Functionalization MethodsOxidative Organic Chemistry Reactions