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Mild Intermolecular Synthesis of a Cyclopropane‐Containing Tricyclic Skeleton: Unusual Reactivity of Isobenzopyryliums
Author(s) -
Liu Shuxuan,
Qian Hui,
Zhang Tianyu,
Xie Hongling,
Han Zhengyu,
Guo Wengang,
Huang Hai,
Sun Jianwei
Publication year - 2021
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.202108258
Subject(s) - cyclopropane , regioselectivity , cycloaddition , chemistry , electrophile , carbenoid , nucleophile , intermolecular force , combinatorial chemistry , reactivity (psychology) , brønsted–lowry acid–base theory , computational chemistry , stereochemistry , ring (chemistry) , catalysis , organic chemistry , molecule , rhodium , medicine , alternative medicine , pathology
Abstract Cyclopropanes embedded in a polycyclic bridged architecture are a versatile structural motif, but such complex frameworks often impose substantial synthetic challenges. Herein we introduce a new approach for the expedient access to such spring‐loaded strained systems via an exceptionally mild intermolecular convergent process between the readily available isobenzopyryliums and vinyl boronic acids. Different from the typical conventional approaches, our protocol does not involve the highly active carbenoid intermediates or strong conditions in order to overcome the disfavored kinetic and thermodynamic problems. Instead, the key cyclopropane ring was formed between the well‐positioned nucleophile and electrophile in the adduct from the regioselective [4+2] cycloaddition. Thus, this unusual process also represents a new reactivity of the versatile isobenzopyryliums. The choice of a Brønsted acid catalyst with proper acidity is crucial to the high efficiency and selectivity for this multiple bond‐forming process. The strained products are precursors to other useful synthetic building blocks.