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Updated: Dec 11, 2025
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Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
Published on: July 17, 2020
From Metallacycle-Mediated Annulative Cross-Coupling to Steroidal Tetracycles through Intramolecular C9-C10 Bond
Adam B Millham1, Chinmay P Bhatt1, Glenn C Micalizio1
1Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States.
Abstract:
While semisynthesis is a common platform for medicinal investigation of steroidal systems, varying the nature of substitution and stereochemistry at C9 and C10 remains challenging. It is demonstrated here that de novo synthesis, enabled by a metallacycle-centered annulation reaction, provides a uniquely effective means of addressing this problem. In short, double asymmetric Friedel-Crafts cyclization proved most effective for establishing anti- relative stereochemistry (with respect to C13), while an intramolecular Heck reaction reliably delivered the syn- diastereomers with high selectivity. In addition, these studies reveal that this oxidative rearrangement is effective for establishing a C10 quaternary center boasting variable alkyl or aryl substitution.
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