3 years ago

Copper-Catalyzed One-Pot Cross-Dehydrogenative Thienannulation: Chemoselective Access to Naphtho[2,1-b]thiophene-4,5-diones and Subsequent Transformation to Benzo[a]thieno[3,2-c]phenazines

Copper-Catalyzed One-Pot Cross-Dehydrogenative Thienannulation:
Chemoselective Access to Naphtho[2,1-b]thiophene-4,5-diones
and Subsequent
Transformation to Benzo[a]thieno[3,2-c]phenazines
Abhijeet Srivastava, Dhananjay Yadav, Maya Shankar Singh, Gaurav Shukla
A facile, cost-effective, and highly efficient copper-catalyzed, TEMPO-mediated straightforward synthesis of 2,3-disubstituted naphtho[2,1-b]thiophene-4,5-diones has been achieved via cross-dehydrogenative thienannulation. The reaction proceeded via in situ generated naphthalene-1,2-diones by dearomatization of β-naphthols, followed by oxidative heteroannulation with α-enolic dithioesters chemoselectively in an open flask. Further, the naphtho[2,1-b]thiophene-4,5-diones undergo l-proline-catalyzed cross-dehydrative coupling with ortho-phenylenediamine enabling pentacyclic benzo[a]thieno[3,2-c]phenazines in good yields under solvent-free conditions. A mechanistic rationale for this cascade reaction sequence is well supported by the control experiments.

Publisher URL: http://dx.doi.org/10.1021/acs.joc.7b03092

DOI: 10.1021/acs.joc.7b03092

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