Rh2(ii)-catalyzed enantioselective intramolecular Büchner reaction and aromatic substitution of donor–donor carbenes |
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| Authors: | Dong Zhu Tongxiang Cao Kai Chen Shifa Zhu |
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| Institution: | Key Laboratory of Functional Molecular Engineering of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640 P. R. China.; College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 P. R. China.; Guangdong Youmei Institute of Intelligent Bio-manufacturing, Foshan 528225 P. R. China |
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| Abstract: | The chiral dirhodium(ii) tetracarboxylate-catalyzed enantioselective intramolecular Büchner reaction of donor/donor-carbenes was reported and a series of valuable chiral polycyclic products were synthesized. Both aryloxy enynones and diazo compounds were efficient carbene precursors for this reaction. Excellent yields (up to 99%) and outstanding enantioselectivities (up to >99% ee) were achieved under standard conditions. For furyl substituted chiral cycloheptab]benzofurans bearing a substituent at the C4 position on cycloheptatrienes, control reactions showed that the chiral Büchner products could slowly racemize either under dark or natural light conditions. A diradical-involved mechanism rather than a zwitterionic intermediate was proposed to explain the racemization. Furthermore, furyl substituted chiral fluorene derivatives were obtained via asymmetric aromatic substitution when biaryl enynones were employed as carbene precursors.The chiral dirhodium(ii) tetracarboxylate-catalyzed enantioselective intramolecular Büchner reaction and aromatic substitution of donor/donor-carbenes were reported and a series of valuable chiral polycyclic products were synthesized. |
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