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Updated: Aug 17, 2026

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones
Published on: February 7, 2019
Triphenylphosphine-mediated reductive cyclization of 2-nitrobiphenyls: a practical and convenient synthesis of
Adam W Freeman1, Marie Urvoy, Megan E Criswell
1Eastman Kodak Company, Research and Development Laboratories, 1999 Lake Avenue, Rochester, NY 14650-2116, USA. adam.freeman@kodak.com
Abstract:
The synthesis of a series of substituted carbazoles from the corresponding 2-nitrobiphenyl derivatives using a novel modification of the Cadogan reaction is described. Cyclization of the 2-nitrobiphenyls was achieved via reductive deoxygenation of the nitro groups using a slight excess of triphenylphosphine in a suitable solvent. We have observed a temperature dependence on the extent of conversion under these conditions, with higher boiling solvents affording higher yields across a range of substrates. The new reaction conditions are very straightforward and convenient to execute, tolerate a broad range of functional groups, and yield carbazole products in the absence of unwanted side products.
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