While Friedel-Crafts (F-C) reaction was widely used for the preparation of functionalized benzylic compounds, the interrupted F-C reaction that allows for the synthesis of stable dearomatized cyclic systems has rarely been reported. We demonstrated herein that the introducing of opportune steric hindrance group around the reactive site of arenes could enable an interrupted F-C reaction by retarding the rearomatization process of the corresponding dearomatized intermediate. Utilizing such a concept, an organocatalyzed dearomative 1,8-addition and formal dearomative Diels-Alder cascade between polycyclic phenols and propargylic alcohols was realized to give efficient access to a series of structurally and stereochemically complex polycyclic diketones. This double dearomatization reaction features a broad substrate scope, exclusive diastereoselectivity, operational simplicity and mild reaction conditions. The preference of the current protocol to undergo a double dearomatization reaction instead of a [3+3] cycloaddition was rationalized by DFT calculations.

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