Dearomatization of aromatic compounds produces highly reactive intermediates and thus affords new opportunities to synthesize novel molecular motifs and complex natural products.Due to the thermodynamic reasons dearomatization is a challenging transformation, even though numerous methodologies have successfully been developed to dearomatize phenols, sulphonamides and other heteroarenes, such as oxidation, alkylation, and acylation. In contrast, limited strategies of the dearomatization of non preoxidized arenes without heteroatoms have been reported. Although arenes are unique substrates to afford complex alicyclic compounds with unmarked functionality, they show poor reactivity for common dearomative methods reported for phenols or heteroarenes. Visible-light-induced dearomatization of challenging non-phenolic 1,1’-biaryl-2-carboxylic acids has been developed. We demonstrate that dearomatization can be performed by either aerobic photocatalytic or anaerobic photooxidative pathway. In both pathways, the dearomatization of the neighboring aryl is induced by electrophilic attack by the carboxyl radical. In order to direct the attack at the ipso position, a twisted conformation of the biaryls is crucial which was achieved by installation of substituents on either or both aryls. The resulting spirodiene radical is captured by either oxygen or water in aerobic and anaerobic systems, respectively, to generate the spirodienone. This method affords a novel route to dearomatization of non-phenolic arenes and spirolactone synthesis.

Visible-light-induced dearomative spirolactonization of non-phenolic biaryl carboxylic acids

2019 Spring National Meeting

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