Ring-opening benzannulations of cyclopropenes, alkylidene cyclopropanes, and 2,3-dihydrofuran acetals: A complementary approach to benzo-fused (hetero)aromatics

Cyclopropenes;Alkylidene cyclopropanes;2,3-dihydrofuran;Benzo-fused aromatics;Benzannulation;Ring-opening;Formal-homo-Nazarov cyclization;Heteroaromatics

Aponte-Guzman, Joel ; France, Stefan Collard, David M. Fahrni, Christoph J. Jones, Christopher W. Oyelere, Adegboyega Chemistry and Biochemistry ; France, Stefan

University:Georgia Institute of Technology

Department:Chemistry and Biochemistry

关键词: Cyclopropenes;    Alkylidene cyclopropanes;    2,3-dihydrofuran;    Benzo-fused aromatics;    Benzannulation;    Ring-opening;    Formal-homo-Nazarov cyclization;    Heteroaromatics;   

Others  :  https://smartech.gatech.edu/bitstream/1853/54953/1/APONTE-GUZMAN-DISSERTATION-2015.pdf

美国|英语

来源: SMARTech Repository

【 摘 要 】

Over the past decades, functional group manipulation of aromatic precursors has been a common strategy to access new aromatic compounds. However, these classical methods, such as Friedel-Crafts alkylations and electrophilic/nucleophilic aromatic substitutions, have shown lack of regioselectivity besides the use of activators in excess amounts. To this end, numerous benzannulations to form benzo-fused substrates via Diels-Alder (DA), ring-closing metathesis (RCM), cycloaddition, and transition-metal-promoted processes have been reported. Appending a benzene ring directly onto a pre-existing ring is preferable to many classical methods due to the likely reduction of reaction steps and superior regiocontrol. However, many of these benzannulation reactions require air- and/or moisture- sensitive reaction conditions, a last oxidation step, or the use of highly functionalized precursors. Here we disclose three ‘complementary’ intramolecular ring-opening benzannulations to access a large array of functionalized (hetero)aromatic scaffolds utilizing cyclopropenes-3,3-dicarbonyls, alkylidene cyclopropanes-1,1-diesters, and 2,3-dihydrofuran O,O- and N,O- acetals as building blocks. More than 70 benzo-fused aromatic compounds were synthesized using this complementary approach with yields up to 98% and low catalyst loadings. With these benzannulation reactions in hand, we aim to open the synthetic door to a handful of bioactive natural products.